# Overheating



## Getyourgoat (Jul 1, 2014)

I have a 1967 GTO with a 1972 455 engine.
It keeps overheating and I can't figure out what to do.
I just installed a new 4 core desert cooler radiator, new rad cap and thermostat.
Any ideas anyone?


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## Goat Roper (Oct 28, 2014)

Lots of info on this thread.

http://www.gtoforum.com/f50/possible-causes-gtos-overheating-15588/


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## Getyourgoat (Jul 1, 2014)

Thanks for the reply. I read the thread and found it very interesting. I'm wondering if my clutch fan is operating correctly. What is the best way to test it?


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## BearGFR (Aug 25, 2008)

One of the most important things, if not THE most important thing, is to make sure your divider plate clearance is correct. If you're not sure, it's worth pulling the pump and making sure.

Bear


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## Getyourgoat (Jul 1, 2014)

I agree. I'm going to pull my water pump of and inspect it. I found a cool video on You Tube that deals with this... https://youtu.be/UdyAo5546JQ
Is the guy in the video on target with what you are talking about?
He recommended 1/10" clearance. 
I have a question about my clutch fan. With the car off and cold, should I be able to turn the fan by hand?


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## Goat Roper (Oct 28, 2014)

That is pretty much it, when I pulled mine off the threads came out on the bolts because some ham fisted mook had over tightened them and one of the two plates was missing and I ordered a new set.
Do not over torque when re assembling 12-15 lbs. is all you need.
Support the pump housing across a vise not by the shaft and tap the plate down around in a circle until the plate just touches the impeller.
Then put the gasket on and spin it to make sure it isn't hitting the plate.

On the fan clutch you should be able to turn the fan when it is cold but there should be quite a bit of resistance.
Google testing a fan clutch for more info.

If you don't have the service manual get one, a quick read through the section pertaining to the repair you are doing will help you avoid many pitfalls.


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## Getyourgoat (Jul 1, 2014)

So, I pulled the water pump off tonight and I can see that it is leaking from the little hole behind the pulley making me think the bearing seal is bad. For this reason, I plan to buy a new water pump. Upon closer inspection of the impeller, I can see almost a 1/4 inch gap between the outside edge of the impeller and the inside edge of the divider plate. I plan to reuse the steel divider plate because I can't find one locally anywhere and the plate show no signs of rust. It has been in the car for more than 20 years. If it hasn't rusted by now, it will probably out live me.
I think that once I get the new pump I will work the divider plate until I can get the utmost minimum amount of clearance possible and then re-install the pump. My only question at this point is what is the best pump available cast Iron or aluminum?
Also, when reinstalling should I use non-hardening permatex, hardening permatex, silicone or nothing at all on the two gaskets?


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## Pinion head (Jan 3, 2015)

Getyourgoat said:


> So, I pulled the water pump off tonight and I can see that it is leaking from the little hole behind the pulley making me think the bearing seal is bad. For this reason, I plan to buy a new water pump. Upon closer inspection of the impeller, I can see almost a 1/4 inch gap between the outside edge of the impeller and the inside edge of the divider plate. I plan to reuse the steel divider plate because I can't find one locally anywhere and the plate show no signs of rust. It has been in the car for more than 20 years. If it hasn't rusted by now, it will probably out live me.
> I think that once I get the new pump I will work the divider plate until I can get the utmost minimum amount of clearance possible and then re-install the pump. My only question at this point is what is the best pump available cast Iron or aluminum?
> Also, when reinstalling should I use non-hardening permatex, hardening permatex, silicone or nothing at all on the two gaskets?


The best pump?
Does your 72 455 have an 11 bolt timing cover and waterpump, or does it have the '67's original 8 bolt timing cover and waterpump?


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## Old Goat 67 (Feb 2, 2009)

One for sale with the correct impeller.
Should not require beating on plate.
Water Pump Pontiac 1959 1960 1951 1962 1963 1964 1965 1966 1967 1968 V8 GM | eBay


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## Getyourgoat (Jul 1, 2014)

Pinion head said:


> The best pump?
> Does your 72 455 have an 11 bolt timing cover and waterpump, or does it have the '67's original 8 bolt timing cover and waterpump?


My water pump is an 11 bolt.


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## Getyourgoat (Jul 1, 2014)

Old Goat 67 said:


> One for sale with the correct impeller.
> Should not require beating on plate.
> Water Pump Pontiac 1959 1960 1951 1962 1963 1964 1965 1966 1967 1968 V8 GM | eBay


Thanks for the reply. The one you linked to on eBay is a re-manufactured pump. I want a brand spanking new one, the best money can buy. I'm not looking for a bargain, I'm looking for best performance and quality. 
I'm confused by your statement about hammering the divider plate. 
Are all of these other folks wrong in telling me to hammer the plate to get a closer fit? 
I agree that I should not have to do any modification to the plate however; looking at the gap that is there now seems to be to wide to work at optimum performance.


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## oldskool (Apr 26, 2015)

"...I want a brand spanking new one, the best money can buy. I'm not looking for a bargain, I'm looking for best performance and quality. 
I'm confused by your statement about hammering the divider plate..."




Most believe that the FlowKooler is the best pump available. Some like the PRW pump. For best results, it's a good idea to reduce the impeller clearance to a min, regardless of which pump you buy. 

http://www.summitracing.com/parts/bra-1649/overview/make/pontiac

http://www.ebay.com/itm/PRW-1445500...ump-/201244921396?hash=item2edb21ce34&vxp=mtr

PRW 1445500 Pontiac 265 455 Hi Flow Aluminum Water Pump | eBay


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## PontiacJim (Dec 29, 2012)

Everybody has a preference as to what is the "best" water pump. It only seems to be the "best" when it cures the overheating situation -which sometimes is not the pump at all (but of course the user though it had to be the pump that was causing the problem and not the divider plate, thermostat, radiator, clutcht fan, fan shroud, etc.) and then you get the "negative" comments on that brand of pump because it did not cure the overheating woes.

The factory pump seemed to work from the factory until it started dripping, right? So there are companies that offer quality rebuild factory pumps. 

Then there are replacement pumps from a host of parts supplier vendors which can be had from your local parts store, but they often have an inferior metal/cast replacement impeller versus the correctly shaped factory cast impeller. These can in some instances create a problem which I think is more related to the additional clearances they create between the impeller and the water pump divider plate.

Next you have the "new & improved" design which includes some unique features such as a "high flow" impeller, whether cast or steel fabricated claiming to cure all your overheating problems and move enough volume of water to fill an in-ground pool in under 15 minutes.

I like the "idea" of a higher flowing water pump, but keep in mind that the flow is restricted by the thermostat opening & closing, and the radiator size (number of core rows, the size of the core tubes, aluminum vs copper, and whether or not the cooling system over-all is free flowing or plugged by years of scale and what not).

If the water flow is too much, it may not sufficiently or efficiently draw heat from the engine (and sometimes why differing pulley sizes are used to speed up or slow down a water pump to match a specific RPM range of your engine). Of course, too slow, and we know what happens here.

So, which is the best water pump money can buy? The one that is advertised the most, finds its way into our favorite car magazines, and makes claims bigger than life so you go out and buy it, "ya buddy, that's the one I gotta have on my car." :thumbsup:

For me, and this is the first one of these I have ever bought other than a factory replacement (rebuilt), is the *Milodon* aluminum 11-bolt water pump. It says it is a "high flow" pump, has "better" bearings, and in my mind ('cause even I get sucked in sometimes by advertisements), is that being aluminum I figured it may slightly produce a small cooling effect due to the nature of aluminum versus cast iron (but I am sure if we scientifically measured it that the difference between the cast and aluminum housings are almost insignificant).

So I went with the *Milodon* piece and got it through Summit. Have not used it, let alone install it, as my project at this point is not ready for its engine installation. Now of course I will be telling you it is the best water pump money can buy because my engine won't be overheating with its aluminum radiator and dual electric fans, right? :lol:


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## oldskool (Apr 26, 2015)

"...the Milodon aluminum 11-bolt water pump. It says it is a "high flow" pump, has "better" bearings..."


You can read LOTS of conflicting info on the net. On the Summit site, a guy says that the Milodon pump is just a reboxed GMB pump, and that he even compared the two. He says the Milodon has GMB cast on it. And, of course, the GMB is much cheaper. So, is this info correct ? I have no idea.

http://www.summitracing.com/parts/mil-16281/overview/make/pontiac

http://www.summitracing.com/parts/gmb-130-1280al/overview/make/pontiac


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## PontiacJim (Dec 29, 2012)

oldskool said:


> "...the Milodon aluminum 11-bolt water pump. It says it is a "high flow" pump, has "better" bearings..."
> 
> 
> You can read LOTS of conflicting info on the net. On the Summit site, a guy says that the Milodon pump is just a reboxed GMB pump, and that he even compared the two. He says the Milodon has GMB cast on it. And, of course, the GMB is much cheaper. So, is this info correct ? I have no idea.
> ...



Yes, that is correct, mine has the GMB cast on it, so same casting. The only difference I can see as advertised is that the GMB pump states "standard volume flow" while the Milodon pump states "high volume" pump flow. Neither pump shows the impeller, but the Milodon I have is a cast iron impeller having 8 blades which are straight cut at the top where some blades can be taper cast/cut. That said, the difference in price may indeed be all in the blade design, but I can't confirm it without a GMB pump. 

I suspect you would not have such a large difference in price between the two due only to the name sake, so my guess is the GMB is a "standard flow" pump as original and then Milodon modifies the same GMB casting for higher flow which is advertised on the outside of the box in big letters as a "High Performance Water Pump." Me, I went for the "high volume" pump flow specification rather than take a chance on saving a few dollars and being disappointed because even though one comment said it was the "same" pump, I could not find any pics showing the two side by side or each manufacturers impeller design - _so same pump housing isn't necessarily the same pump._


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## oldskool (Apr 26, 2015)

I have never bought either a Milodon or a GMB pump. All I have to go by is what I read. Amazon has a pic of the GMB impeller, and says it is a high flow design.

[ame]http://www.amazon.com/GMB-130-1280AL-Replacement-Aluminum-Water/dp/B006D1VS06[/ame]


For those who didn't read it, here is a copy of what the guy on the Summit review said.

"I'm gonna go ahead and save you about 44 bucks right now - this is nothing more than a GMB pump that has been placed into a Milodon box. Period. No changes whatsoever. It even has GMB stamped on the housing and on the shaft. I ordered a GMB pump and compared them side by side and it confirmed my suspicions. They were absolutely identical in every way - housing, shaft, impeller, everything. The price for the "Milodon" pump, though, was over twice as much as the GMB. I am also a bit confused as to how GMB labels this pump standard-volume and Milodon is able to get away with labeling it high-volume. It's the exact same product! Really disappointed in Milodon over this one."

So, is this guy just lying about it ? Or is the impeller and everything else about the 2 pumps exactly the same, as he says ? I don't have a clue.

Not all Pontiac pump impellers are created equal. Some are stamped, which are said to be the worst kind. Some are cast, with different size, number and shape fins. PRW claims theirs is CNC machined, tho I cannot find a pic of one. 

Then there is the FlowKooler, which has an impeller which appears to be made of some type of plastic material, with straight fins. I'm not sure what material the impeller is made of ? This may answer that question. "...Each machined impeller is protected with an Type II Military Grade anodized surface coating..." I assume this impeller is why they can get away with the higher price of their pumps.


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## PontiacJim (Dec 29, 2012)

oldskool said:


> I have never bought either a Milodon or a GMB pump. All I have to go by is what I read. Amazon has a pic of the GMB impeller, and says it is a high flow design.
> 
> http://www.amazon.com/GMB-130-1280AL-Replacement-Aluminum-Water/dp/B006D1VS06
> 
> ...



Hmmm. OK, I took a look. Yep, everything does indeed look identical as I match my Milodon pump (which is right in hand) with the Amazon pic. The part numbers on the end of the water pump shaft are even the same. What I do see in difference, however slight, is that the impeller in the Amazon pic has a machined ring just outside of the impeller blades. If you look at it, part of that ring is machined smooth while other sections appears to be rough casting, and I don't think it is from the angle or light. The Milodon pump has the ring completely machined smooth, ie no casting appearance.

Again, tough call when I don't have one physically in hand and it is easy enough to swap pics to represent something or photo shop something - and I'm not saying this was done or not. Have you ever been served a burger or subway sandwich that looked like the photo of what you were getting? So the jury is out on this one. :confused


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## the65gto (Oct 9, 2008)

The irritating thing about most of these vendors is that they never show you the working part of the pump, the impeller. IMHO, I like cast impeller, individual vanes that run the full length from inside to outside and the vanes have a rounded top.


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## Getyourgoat (Jul 1, 2014)

PontiacJim said:


> Then there are replacement pumps from a host of parts supplier vendors which can be had from your local parts store, but they often have an inferior metal/cast replacement impeller versus the correctly shaped factory cast impeller.





PontiacJim said:


> Neither pump shows the impeller, but the Milodon I have is a cast iron impeller having 8 blades which are straight cut at the top where some blades can be taper cast/cut.[/U][/I]





the65gto said:


> The irritating thing about most of these vendors is that they never show you the working part of the pump, the impeller. IMHO, I like cast impeller, individual vanes that run the full length from inside to outside and the vanes have a rounded top.



Thanks to all for their input. From what I understand from all of this is that people tend to like a pump that has a cast impeller. Based on what "PontiacJim" said, it sounds like the Milodn has a cast impeller so I'm assuming the GMB impeller is cast as well, not sure. Also, what is the shape of the Milodon/GMB impeller. Is it the "correctly shaped factory cast impeller". Is the impeller mentioned by "the65gto" the factory shape.
Looking everywhere I can on the internets for a pump, I have yet to find one that specifically states that the impeller is cast or factory shape. Does anyone know who makes a pump with a "cast impeller/factory shape/factory number of blades" for sure?


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## Old Goat 67 (Feb 2, 2009)

Getyourgoat said:


> Thanks to all for their input. From what I understand from all of this is that people tend to like a pump that has a cast impeller. Based on what "PontiacJim" said, it sounds like the Milodn has a cast impeller so I'm assuming the GMB impeller is cast as well, not sure. Also, what is the shape of the Milodon/GMB impeller. Is it the "correctly shaped factory cast impeller". Is the impeller mentioned by "the65gto" the factory shape.
> Looking everywhere I can on the internets for a pump, I have yet to find one that specifically states that the impeller is cast or factory shape. Does anyone know who makes a pump with a "cast impeller/factory shape/factory number of blades" for sure?


It's a crap shoot.
Buyer beware! Accept NO substitutes!

BAD Impeller first. GOOD second. NEVER overheats now.


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## geeteeohguy (Feb 2, 2008)

You want a cast iron, cast impeller pump. Use a little silicone or RTV on all the gaskets. A LITTLE. I've managed to re-gap some plates without beating.....simply by using a crescent wrench as a forming tool and going around the perimeter gently. Good luck.


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## PontiacJim (Dec 29, 2012)

Getyourgoat said:


> Thanks to all for their input. From what I understand from all of this is that people tend to like a pump that has a cast impeller. Based on what "PontiacJim" said, it sounds like the Milodn has a cast impeller so I'm assuming the GMB impeller is cast as well, not sure. Also, what is the shape of the Milodon/GMB impeller. Is it the "correctly shaped factory cast impeller". Is the impeller mentioned by "the65gto" the factory shape.
> Looking everywhere I can on the internets for a pump, I have yet to find one that specifically states that the impeller is cast or factory shape. Does anyone know who makes a pump with a "cast impeller/factory shape/factory number of blades" for sure?


Look at post #16 by oldschool. Click on the "Amazon" link he has up. This will take you to the GMB aluminum pump which shows the cast iron impeller. The Milodon pump I have is a GMB pump and has the same cast impeller being it seems to be made by GMB for Milodon for re-sale. However, I noted what I saw as a questionable difference but cannot verify if there really is a difference. The GMB pump is much cheaper and I find it hard to believe that Milodon would simply re-box the same GMB pump as their own without providing some change or form of betterment of the GMB pump itself. Either way, both have the cast impeller. And like I said in the beginning, everyone has an opinion as to what is best and what sucks.:thumbsup:


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## oldskool (Apr 26, 2015)

*GMB Impeller Pic*

"...what is the shape of the Milodon/GMB impeller..."

This Ebay ad has several pics of a GMB pump, including the impeller. At least that's what the pics are supposed to be. 


Engine Water Pump GMB 130 1280AL | eBay

This PRW ad states that it has a CNC machined cast impeller.

PRW 1445500 High Flow Aluminum Water Pump 1969 1979 Pontiac 265 455 GTO LeMans | eBay

This PRW ad on Amazon has a review in which a guy says that the impeller is similar to stock, but has more fins, for higher volume and better flow.


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## the65gto (Oct 9, 2008)

Look at some of these "variations" closely. Last pic is a non cast(POS):eek2:


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## Getyourgoat (Jul 1, 2014)

*Problem Solved! No More Overheating!*



BearGFR said:


> One of the most important things, if not THE most important thing, is to make sure your divider plate clearance is correct. If you're not sure, it's worth pulling the pump and making sure.
> 
> Bear


I finally bought a new water pump with cast iron impeller and a divider plate from Ames Performance. I then made the clearance modification to the divider plate and now I'm running about 20 degrees cooler! Thanks for everyone's help!


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## Getyourgoat (Jul 1, 2014)

I think that maybe I spoke too soon. I was out driving yesterday with your conditioner on and it started to overheat again. I turned the AC off and it did cool down a little bit. I've done everything I know to do to this car and still have the same overheating issue. So I have a new 4 core radiator and water pump. Tried different thermostats. Nothing seems to work. any suggestions would be appreciated.


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## Getyourgoat (Jul 1, 2014)

I'VE GOT TO FIX THIS OVERHEATING PROBLEM SOON OR MY WIFE IS GOING TO MAKE ME SELL THE CAR!
She feels neglected 

The car overheats to the point of puking anti freeze into the catch tank and then out the overflow. 
Temp gauge reads 230 in town or on the highway and checking with a laser thermometer at the sending unit reads about the same.
Doesn't seem to matter if the Air Conditioner is on or off.

Here's what I've done so far...
1. Replaced radiator with a 4 core. Flushed system and burped the air out.
2. Replaced thermostat with a 180 degree stat.
3. Replaced 7 pound Rad cap.
4. Replaced upper and lower hoses.
5. Installed new water pump and did the divider plate clearance modification.
6. Added a bottle of water wetter.
7. Used heavy aluminum tape and closed off air gaps around fan shroud.
8. Replaced temp sending unit.
9. Tested fan clutch. Seems to be OK but I ordered a new one anyway. It should be here in a few days.
10. I'm going to check the timing. Aside from the heat issue the car runs like a champ, so I'm a little hesitant about jacking around with the timing.

The motor is a 1972 455 with a TH400 tranny.
Anyone know what the timing should be set to?
Any other ideas on how to get this beast to cool down?
For this particular motor, what should the normal operating temp be with and without the AC running?


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## PontiacJim (Dec 29, 2012)

Hmmmm, seems you have covered it all. Strange that it was running OK and then it heated up on you.

You replaced the 7lb radiator cap with a 15 lb, right? This is based on my 1968 Service Manual - 1968 and later used the crossflow type radiators. It also says it will raise the boiling point to 258 degrees at sea level. Keep in mind that the radiator should not be filled to the top as the antifreeze needs space to expand when hot. Again, Service manual says 3" below filler neck when cold, 1" below when hot.

My thoughts are the thermostat because it is pushing back out the radiator. I have had nothing but bad luck with these on my '97 Toyota. They work for a couple weeks, then won't open. Been through 3 of them. Finally just pulled the thermostat out, removed the center section by cutting the lower tabs that hold it in and re-installed the metal ring, less the guts, to act as a restrictor plate and support the O-ring type gasket. Runs really cool at moving speeds with air going through the radiator & will warm up to "operating" temp in local stop/go traffic.

That said, I would get a cheapy thermostat from the local parts store, cut the center element out, and install just the metal outer ring to see if that makes a difference. If it does, then you know where your problem lies.

It could still be the fan clutch, but you have a new one coming, so one more elimination. Do you have the 19 1/2 diameter 7-bladed fan? Again, 1968 Service Manual.

There was one poster here that had a lean condition that was causing overheating. His engine was built, and it needed more gas to feed it. Q-jet initial setting is to screw in the idle mixture screws, gently, until it bottoms out. Then screw out 6 turns. Screw in to lean the mixture out, but don't do this as you want to run rich to see if it makes any difference. I don't know how many turns it takes to get the screw completely out, but I might go 7 turns if it will take it. 

You also want to make sure you have a good clean air filter as one that is dirty or restrictive will cut airflow down and cause the engine to run lean. I prefer and open element air cleaner/filter and as big as I can fit.

Idle speed with TH-400 in "D", A/C off is 500 RPM when fast idle electric solenoid is not energized and 650 RPM's when it is. If you don't have the solenoid, then 650RPM's is what you want to shoot for (manual trans is higher @ 850 RPM's). Sometimes idle speed needs to be higher with a performance cam. Do you have the electric fast idle solenoid on your carb?

Timing is 9 degrees BTDC with vacuum hose disconnected to distributor & plugged -for stock engines. This can vary based on cam. What you want to shoot for is *Total Timing* which seems to be around 30-34 degrees for a Pontiac @ 2300-2500 RPM's It is also important to have the correct vacuum advance in the distributor in relation to your engine.

I found this tip on the internet that might also help you, "I prefer direct manifold vacuum over a ported source as found on most carburetors. This pulls in more timing at idle which is good since there is virtually no load. Your motor will idle smoother and cooler with the extra timing. One night I was at the drags and my car was running hot in the staging lanes, I swapped the vacuum advance from ported to manifold then it would idle all night at 175°. Believe it or not the purpose of ported vacuum is to raise the temperature at idle, to lower NOx emissions. If you're like most hotrodders that is of no concern to you. If you have a big cam with a choppy idle then a vacuum advance hooked to manifold vacuum can really help. It will idle smoother and requires less throttle to maintain speed. Often a big cam requires you to open the throttle so far that the curb idle adjustment needles won't work. Hooking the vacuum advance to manifold vacuum will allow you to close the throttle some which may be enough for the idle mixture screws to work."

Attached is the *Secret & Restricted* specs never before released to the general public for fear the Chebby guys would get a hold of it- yes folks, info like this comes right out of the Pontiac Service Manual which each and every one of you should have either for yourself or the guy who works on your car. Note that these specs are given per the _distributor model number_ based on engine application and model of car. Don't know which each fits, but we can use this as an example for all. And, just to throw off the Chebby guys, timing is listed by _distributor degrees_ which is 1/2 of crankshaft degrees, ie centifugal advance distributor degrees @ 13-15 degrees is 26-30 @ crankshaft degrees on your balancer.

OK, we will use the second block, dist #1110431 as our example Lets begin with the factory setting of 9 degrees BTDC initial crankshaft timing found on your balancer - *Idle Timing*. To that we add the Centifugal/Mechanical Advance, 12 distributor degrees/24 crankshaft degrees @ 2500 RPM's for a *Total Advance* timing of 33 degrees (9+24=33) @ 2500 RPM's as found on your balancer. It is easy to see that if you advance your timing 3 degrees to 12 degrees BTDC, you will affect your total timing the same amount for a Total Advance of 36 degrees.

Now if you wanted to go 14 degrees initial timing, our total timing would be 38 degrees. This might be way too much @ 2500 and we could experience detonation. The mechanical advance/weights in the distributor could be made so they do not advance to give us any more than 34 degrees total advance. This is where fine tuning comes in and a little mechanical know how helps. The rate of how quick the distributor weights advance the timing (timing curve) and at what RPM this happens can be adjusted with assorted springs - light, heavy, or a combination of each. Again, some trial and error required here as your car/engine combo might like its total advance to be reached at 3000 RPM's instead of 2500 RPM's. Use the factory settings to get you going and then adjust from thee if you feel you need to. :thumbsup:


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## Goat Roper (Oct 28, 2014)

I did it all and still had overheating until I replaced the cheapo fan clutch with a new HD one.
Yesterday I took the car for a drive up the mountain with the A/C running and the hottest it got was 205 degrees.
I am running a 195 degree thermostat.
I found out that my alternator was marginal, it could keep up with nothing on but with the blower going and the headlights on it was draining the battery.
Local parts store had one delivered by 3 pm and another run around the lake at 4pm and now I am getting 13.5 with everything running.
Just cruising with no steep hills it was running right at 200 degrees.


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## Getyourgoat (Jul 1, 2014)

> You replaced the 7lb radiator cap with a 15 lb, right? This is based on my 1968 Service Manual - 1968 and later used the crossflow type radiators. It also says it will raise the boiling point to 258 degrees at sea level. Keep in mind that the radiator should not be filled to the top as the antifreeze needs space to expand when hot. Again, Service manual says 3" below filler neck when cold, 1" below when hot.


WOW! Thanks for all the info guys.
You mentioned stuff based on the 68 manual.
So I don’t get myself confused here, I should mention that when I first got the car, it had no engine and no transmission.
My Dad gave me a 455 with a TH400 that came out of a 1972 Grand Prix. Having said that, I’ve referred to a manual that covers the 1972 Grand Prix for engine/transmission/cooling information.
I’ve been referring to a 67 manual for everything else.

The radiator did not use a catch tank and would simply overflow to the ground. The radiator was bad so I decided to replace it and install a catch tank.
I bought a 4-Core High-Efficiency Desert Coolers radiator from Ames performance and found it was manufactured by US Radiator in California (Ames part number p119amh, US Radiator part number 027290aanz).
When I installed the catch tank, I filled the radiator all the way up to the top and added about 4 inches of anti-freeze to the catch tank. Right now, I’m using a 7 lb. cap. I tried a 15 lb. cap and it didn’t make any difference.
If I’m using an overflow catch tank, shouldn’t the radiator be filled all the way to the top?
Should I switch back to 15 lb. cap anyway?


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## Goat Roper (Oct 28, 2014)

_If I’m using an overflow catch tank, shouldn’t the radiator be filled all the way to the top?_

No, 2-3 inches from the top is where it should be to allow for expansion.
Yes on the cap, use the 15 lb unit and test it to make sure it really is a 15 lb cap.


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## Getyourgoat (Jul 1, 2014)

I will give that a shot. I'm also going to go ahead and replace the clutch fan. But all that's going to have to wait until next weekend. Thanks for the info!


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## PontiacJim (Dec 29, 2012)

GYG: "You mentioned stuff based on the 68 manual."

PJ: Yep, just for reference, but gives you an idea of what some things should be as they usually don't change a lot.

GYG:"My Dad gave me a 455 with a TH400 that came out of a 1972 Grand Prix. Having said that, I’ve referred to a manual that covers the 1972 Grand Prix for engine/transmission/cooling information.
I’ve been referring to a 67 manual for everything else.

PJ: OK, that should work. It should answer many of the questions you asked previously about timing, carb settings, radiator cap pressure, fan, etc.. If it doesn't then you are using the wrong book.

GYG:"Right now, I’m using a 7 lb. cap. I tried a 15 lb. cap and it didn’t make any difference.
If I’m using an overflow catch tank, shouldn’t the radiator be filled all the way to the top?
Should I switch back to 15 lb. cap anyway?"

PJ: Have no idea why you would use a 7 lb cap? Your 1972 manual should specifically tell you what pressure cap to use - which my guess is 15 lbs UNLESS the radiator manufacturer says differently. The higher pressure cap raises the boiling point. Running around 185 - 205 degrees should be good. 215 for short periods is OK, but only short periods, not steady driving. Hot outside temps may have an effect on cooling depending on your system. Remember, a 50/50 mix of antifreeze boils at 223 degrees - no radiator cap. With a 7lb cap, boil over occurs around 240 degrees, with 15lb cap, about 260 degrees. The difference in your engine running at 230 degrees with a 7lb cap and 230 with a 15lb cap, is that the boil-over point has been raised by using the 15lb cap which will keep coolant in the system and not dump it into the catch can. 

As your radiator/coolant heats up, it builds pressure - basic principals of expansion of a liquid. If the antifreeze escapes at a lower boiling point/cap pressure, it lessens the amount of antifreeze left in your system to cool the engine. The engine continues to get hotter and pukes out more coolant. Soon you don't have enough coolant in the system and "hot spots" form and can even produce steam - which increases more pressure which further pushes out the cap/overflow UNTIL you coolant can no longer cool the engine, it overheats at best, or boils out beyond any fluid left to boil over and you warp heads, blow head gaskets, crack things, overheat the oil where it no longer acts as a lubricant and you damage bearings & parts, and overheat the trans fluid to where it no longer cools your TH-400 and burns up the fluid which damages the TH-400 internals.

I think that covers it. Hopefully you will figure this out and it will be something simple. :thumbsup:


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## Goat Roper (Oct 28, 2014)

PJ I found that putting in a lower temp thermostat actually made my car run hotter so I went back to the 195 degree unit.
I think it was because the coolant was running through the radiator so fast it wasn't in there long enough for the radiator to dissipate the heat, thermostat running wide open and the temp just kept building.
The 195 slowed it down enough for the radiator to do it's job.
I also needed a new fan clutch now it runs at 205 with the A/C on, 200 with it off.
YMMV.


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## Getyourgoat (Jul 1, 2014)

> If I’m using an overflow catch tank, shouldn’t the radiator be filled all the way to the top?
> 
> No, 2-3 inches from the top is where it should be to allow for expansion.
> Yes on the cap, use the 15 lb unit and test it to make sure it really is a 15 lb cap.


I'm using a 72 Chilton's manual that doesn't say jack about coolant levels.
I think I'm confused about closed vs open cooling systems.
For Example: On my 2008 Dodge Ram, the radiator is connected to a catch tank. When adding anti-freeze, the manual says that you should only add coolant thru the overflow catch tank and the radiator should remain full. I just checked it and sure enough, the radiator is filled to the top.
SO... I understand that coolant will expand when hot however; isn't the catch tank setup on my GTO basically the same setup as my truck?
I'm probably wrong but I thought an open system was basically a radiator without a catch tank and the fill level should be about 2" from the top.


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## PontiacJim (Dec 29, 2012)

Getyourgoat said:


> I'm using a 72 Chilton's manual that doesn't say jack about coolant levels.
> I think I'm confused about closed vs open cooling systems.
> For Example: On my 2008 Dodge Ram, the radiator is connected to a catch tank. When adding anti-freeze, the manual says that you should only add coolant thru the overflow catch tank and the radiator should remain full. I just checked it and sure enough, the radiator is filled to the top.
> SO... I understand that coolant will expand when hot however; isn't the catch tank setup on my GTO basically the same setup as my truck?
> I'm probably wrong but I thought an open system was basically a radiator without a catch tank and the fill level should be about 2" from the top.


Ah, you are definitely not using a FACTORY Service Manual. Yep, you are WRONG. Apples and Oranges, 1967 & 2008 - completely different systems and principals. You probably also have aluminum in the engine to aid in cooling? You should not need an overflow/catch can on the '67. The 2008 may not have an expansion tank at its top or it is very shallow? So the expansion tank is actually the catch tank which you use to fill/top-off the radiator. The catch tank gets filled as the antifreeze expands (and pushes any air out of the system - like when you open the cap and fill it up) when hot. Conversely, when the engine cools and the coolant contracts, it sucks the antifreeze back out of the catch can and back into the radiator BECAUSE the radiator cap is designed to allow the fluid to be drawn back in. If the cap did not have this feature, you would see your hoses collapse as the coolant contracted. To the best of my knowledge, all caps work this way, but your radiator should have a large enough area at the top (or sides if a cross flow) to compensate for this expansion under NORMAL conditions or UNLESS your aftermarket tank is designed to use a catch can AND it is what the manufacturer recommends. Otherwise, you have a coolant issue and the coolant is being pushed out the overflow at a rate greater than what the expansion tank is designed for leaving you with a less than required amount of antifreeze in your system to keep the engine cool the next tie you run it - eventually boiling out additional antifreeze and causing the engine to overheat real fast in short order. 

You may have already blown a head gasket or cracked a head and if this has happened, you don't necessarily see oil in your water or water in your oil. You could be simply pushing compression into the cooling system which in turn pressurizes the cooling system and pumps the antifreeze out the radiator through the cap. Had this happen on my '97 Toyota and had to just about argue my point with the mechanics who insisted a cracked head or block, but I had oil going into my coolant and no coolant in my oil. Ran it this way for months. They didn't want me to waste my money on such an old high mileage car. OK, I get it, but I told them to replace the head gasket and they were going to get paid either way - good or bad. Sure enough, head test good at a machine shop with no cracks or warpage, block had no cracks - head gasket went bad between an oil pressure passage to the head and a water circulating hole (oil has more pressure than the coolant system and why I figured it was a head gasket). New head gasket and I was up and running and the shop was essentially apologizing to me because they were sure it was a cracked block - I didn't fall off the turnip truck yesterday.

You might consider a local shop to do a radiator test to see if you system holds pressure when pressurized. :thumbsup:


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## PontiacJim (Dec 29, 2012)

Goat Roper said:


> PJ I found that putting in a lower temp thermostat actually made my car run hotter so I went back to the 195 degree unit.
> I think it was because the coolant was running through the radiator so fast it wasn't in there long enough for the radiator to dissipate the heat, thermostat running wide open and the temp just kept building.
> The 195 slowed it down enough for the radiator to do it's job.
> I also needed a new fan clutch now it runs at 205 with the A/C on, 200 with it off.
> YMMV.



I have heard/read this can happen if the flow is too great. I think it is also based on the tube size/material used & core size. My experience has been that without the T-stat, the engine takes longer to warm up, runs cooler as long as moving, and will climb to a point where it normalizes to the engines operating temperature. If the radiator is clogged or too small for the engine, the temp will continue to rise and overheat in stop/go traffic or at extended idle.

But, without the T-stat, you know you will have full flow and the T-stat is not stuck closed or working intermittently. Just another test you can perform and observe the results and go from there. GYG stated his car was running fine and then started overheating, so it could be a bad T-stat when it was running OK and then decided to run hot. Just sayin' :thumbsup:


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## Goat Roper (Oct 28, 2014)

He may have a bad T-stat, I had one that was bad out of the box.
I took it out and tested it in a pot of water bringing it to a boil and it never opened.
If it was running okay and suddenly started to overheat a bad T-stat is definite possibility.
My car came from the factory without a puke can and with the radiator at the proper level it doesn't need one.
If it ain't broke don't try to fix it.


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## Getyourgoat (Jul 1, 2014)

Goat Roper said:


> use the 15 lb unit and test it to make sure it really is a 15 lb cap.


Can I use a 16lb cap?
My manual doesn't tell me what to use. I called NAPA & O'Reilly's and was told all they list for the 72 Grand Prix 455 is a 16lb cap.
Autozone says they can order a 15 lb cap however; I don't want to wait 3 days to get it.


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## Goat Roper (Oct 28, 2014)

Yes, you can go with a 16 lb cap.


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## Getyourgoat (Jul 1, 2014)

So, I installed a new clutch fan and replaced my 185 degree thermostat with a 160 degree thermostat and installed a 16 lb radiator cap. I also dropped the water level in the radiator by 1 inch thus leaving 3/4" water still covering the core. Now, If I'm reading my gauge correctly and assuming it is calibrated correctly it looks like I'm never going over 183 degrees.
I ran the car a 3 mile circle around town which was a 3/4 mile stretch of highway at 90 mph and then exit to side street for 2 1/2 miles stop and go (20-30 mph) and then back on the highway. I did this route 3 times with the AC on and the outside temp was about 90 degrees.
Does 183 degrees sound acceptable? 
What about my water level?
If I drop it down more than 1 3/4" from the filler opening I will be exposing the core. I know that can't be right.


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## Goat Roper (Oct 28, 2014)

Great, 183 is actually on the cool side and your water level sounds perfect.


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## Getyourgoat (Jul 1, 2014)

As I mentioned earlier, I used heavy aluminum tape to close off air gaps around fan shroud. The area I'm referring to is a 1" gap between the fan shroud and the radiator that extends along the top of the radiator from one side to the other. I think it helps but it looks like crap in my opinion.
Did the GTO (or 72 Grand Prix) originally have a rubber piece that covered this area or was it meant to be open?


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## PontiacJim (Dec 29, 2012)

Looks like you got the engine cooling right. 183 degrees is fine. Anything under about 205 is acceptable, but I like to run cooler as yours is right now. Cooler also keeps detonation away.

I don't think there should be any gap in the fan shroud as it should fit flush against the radiator to seal - that's what it is supposed to do. Any gap would allow air to be draw through the gap rather than the radiator. Sounds like the wrong shroud, is it even a Pontiac shroud?. Check the internet. I see on Ebay that there is a new manufactured radiator shroud specifically for a 4-core radiator. I assume the thickness of the radiator would change the position of the fan within the shroud (?), so there must have been one that was a bit thinner to compensate for the thicker 4-core radiator - just guessing here.

Do a little searching for GTO radiator fan shrouds to get an idea of what yours should look like. I would think that if you got a radiator to fit the '67 GTO, then that would be the shroud you would want, just make sure the opening matches your fan diameter.


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## Getyourgoat (Jul 1, 2014)

Well I'm back to the drawing board again. I ran a little test drive around town and on the highway today with the air conditioner running. The temp out side is 79 degrees. When I pulled back into the garage, I noticed the temp gauge was between the 210 mark and the 250 mark, so I figure it was actually running at 230 degrees. I shot the temp sending unit with a laser thermometer which read 224 degrees. I did see a wee tiny bit of coolant in the catch tank, just enough to cover the bottom. Good Grief. I have no idea what to do next. Any thoughts welcomed.


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## PontiacJim (Dec 29, 2012)

You gave up too quickly on the laser temp gun. You need to draw up a chart of your engine/radiator/cooling system and get a crap load of different readings. What was your lower hose temp, upper hose temp, four corners on the radiator, front of each head, back of each head, water pump temp???????

Do this when it is warmed up to get a base reading, maybe a couple times. Then get it as soon as you see the temp begin to go up, pull over someplace safe and take readings. Take a reading as soon as you shut the engine off, then another reading about 10 minutes later to see if any hot spots show up. Then fire it back up, and see if any of the hot spots cool off.

You want to confirm actual temps and not what your gauge reads. Everything was running fine, then went bad? Again, I'd be suspect of the thermostat even though you put in a new one, so check the upper rad hose/lower hose temps.

Next thing would be to take it to a radiator shop or mechanic who can pressure test/leak down test your system to see if you don't have a leak inside the engine, ie bad/weak head gasket. If everything else turns out good........then rip out your temp gauge so it will never trouble you again and drive the car and forget about it. If something goes, you'll know what the problem was. :thumbsup: 

Other things could be:

The water pump impeller slipping on the shaft.

Wrong fan belts - too narrow and sits too deep in the pulley grooves and they can slip. Aftermarket belts can indeed be narrower than the original style so the sit deeper in the pulley and ride on the inside of the pulley and slip rather than grip the pulley at the outside edged as they should. 

Re-check your belt tension as they may have stretched a little from running the car.

Check you timing again to make sure it has not retarded or is off.

I suppose you could have something "floating" around in the coolant system that gets lodged somewhere to cause the overheat and then dislodges again and it runs fine until it plugs something up again - like a piece of gasket or something.

Just gotta keep at it.


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## Getyourgoat (Jul 1, 2014)

Today it's 64 degrees outside. Today, I changed the timing from 8 degrees BTDC to 10 degrees BTDC as specified in my manual for a 1972 455 "engine code YC".
Next I went out for a test drive for about 40 minutes racing up and down the highway. Below is a picture of my temp gage. If my gauge calculations are correct, the midway point between the 100 degree and 210 degree mark would be 155 degrees. The entire time I was running on the highway at lightning speeds, the temp gage hovered around 155-160 degrees. When I exited the highway, traffic was heavy and I had to wait thru 3 changes of the traffic light before returning to the highway. While sitting at the light, the temp jumped to about 200 degrees as seen in the picture. Once I was back on the highway, it immediately dropped back to 155-160 degrees where it was before. When I got home and sat in the garage idling, the temp went back to about 200 degrees. Is it normal for such a fluctuation? Any late model car I have ever driven does not fluctuate between highway and surface streets with traffic stops. Does the temp readings that I've been mentioning look accurate according to this picture of the gauge? Am I running to cool now? My heater puts out great heat.


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## PontiacJim (Dec 29, 2012)

First off, the accuracy of the gauge is just "OK" at best. To get a better reading, you really need an aftermarket temp gauge made by a quality manufacturer such as Stewart Warner, VDO, Autometer, etc. along with _their_ sensor which will be matched to the gauge.

(Another thing to consider is the placement of your temp sensor. If it is located in the head, the gauge may run/show hotter than if located in the intake.)

Second, and this happens a lot, you are so used to the "modern" cars which is like comparing apples to oranges, that you become overly sensitive to the "old" car quirks which in fact can be normal for that era car. I go through this a bunch with my brother who is used to owning/driving contemporary cars then hops in his '73 Plymouth or '57 Caddy and feels that something is amiss until I tell him, "no" that rough shift in those transmissions is normal or the brake pedal needs more pressure to stop than my "X" cars - and that is normal. So don't get into the mode of comparing the "new" with the "old" as it will drive you crazy and you won't enjoy the car. I tell my brother to drive the old car a lot more and get used to it rather than his new car, and stay out of the new car for a while.

Next, your temps look normal and act normal. Going down the road with air passing through the radiator is what keeps it cool - period. If it wasn't cool, then I'd be worried. So 155-160 degree temps at lightning speeds could not be any better. But again, you are too used to the "new" cars which also have a lot more aluminum in the engines, whether it be the block, heads, intakes, or a combination of all of the above. *Aluminum cools off much quicker as it does not hold heat.* Cast iron on the other hand is not only heavier, but retains heat and takes less time to build it up. So going down the highway at lightning speeds is putting heat into your engine, but the cooling system is capable of maintaining a good low temp within the cooling system. Now you slow down, there is still heat building in the engine, but the flow of air through the radiator and water pump slows down and the cooling system reacts accordingly - water temperatures go up. You are now relying on both air flow through the radiator ( which is now low) and the fan (with the fan drawing more air than the forward movement of the car passing air through the radiator). So stop & go driving, or low speeds will increase water temps - moreso sometimes if you just got done driving your car at lightning speeds just before stop & go or slow speeds. If the temps stay under 220 degrees on a hot stop & go day, then you are still OK. Keep in mind that the engine is under a load even when stopped if you run an automatic. The engine is fighting to turn the torque converter which is resisting the engine - so heat is building up in both the engine & transmission. You might want to put the car in neutral when at a stop which will help to cool the engine and you should see the temp gauge drop a slight amount or at least remain steady and not climb.

When you shut the engine off, expect to see temperatures climb. There is no coolant circulation in the engine and the heat will be thrown off into the coolant where it will pick up this heat and continue to rise. That is normal. Cast iron holds heat for a long time. 

In conclusion, your radiator & cooling system are performing the way they should at running speeds - no problem there at all. The problem, if any, is at lower speeds which might indicate that you need to get more air drawn through the radiator by the fan system. Under 200 degrees is not a problem.

One more thing to consider- You also mentioned you set your timing to 10 degrees. Keep in mind that advancing your timing will also advance your total timing which will also have an effect on your vacuum advance. There is nothing wrong with advancing the timing as long as the car runs good and you do not get any detonation issues. You can go to 12 or 14 as long as you don't have any detonation issues under a load like going up a hill or under full throttle. But, you need to know what your full advance is to make sure you are not going too much on your total timing. Then you need to know how much additional timing is being added by your vacuum advance at the distributor. Both of these can be adjusted/limited. These things can also affect water temperatures - your vacuum advance could also be bad.

:thumbsup:


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## Getyourgoat (Jul 1, 2014)

Thanks for the reply Pontiac Jim. The local weather forecast says that it should get to 87 on Tuesday. I'll put her thru the paces again on Tuesday just to see if outside temp makes any difference. I love being a 67 Goat owner even though I've had a lot of problems, I'm getting them all worked out one by one. Yesterday, I pulled up to a stop light next to a new corvette. I could tell the guy was salivating as he eyed my Goat Cart. He should have saved his corvette money and bought a real car, like my 67. IMHO Nothing impresses any more than old school hot rods. Thanks again, your post was very informative.


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