# '66 GTO water pump exploded under acceleration



## ragtopgoat (Sep 26, 2019)

I thought I would share this with folks, as I had never seen anything like this before. I had my '66 out for a cruise on Sunday, and while I was getting on the freeway under hard acceleration, I heard a loud bang under the hood, followed by some bits and pieces scattering in my rearview mirror. The batt light immediately lit up, so I knew I lost belts, but the engine was still running. Not sure what I was dealing with, I watched oil press and temp carefully as I looked for the nearest exit. Once on the exit ramp, it was clear I lost power steering too. I carefully got off the fwy and parked the car in a safe place. At this point, the temp was rising (I figured due to no belts on water pump). By the time I pulled to a stop, steam was coming out under the hood, temp on the gauge never got above 200 or so (I have a 160 thermostat). Popped the hood and was astonished by what I found. The nose of the water pump was gone, along with the fan and pulley. The fan came to rest near the passenger wheel well. The plastic fan shroud was mostly gone, which accounted for the pieces I saw scattering in the rearview mirror. Pictures attached. 

I'm wondering has anyone ever seen this sort of catastrophic failure before? I am sure that I had the belt tension set where it should be. I have a Powermaster alternator, and adjusted the belt to that per their recommendations. I also use a belt tension gauge to check the tension, so I'm reasonably confident that I didn't have the belts tightened to some crazy level. Is this just fatigue failure of an old part? I'm not sure of the age of the WP, probably not likely original, but I'm guessing it could be decades old. 

As you can see from the pics, I'm going to need a new water pump, fan, pulley, crank pulley and I'll replace the timing cover while I'm at it, as it is very old and the inlet pipe is scarred pretty badly. Let me know if you can suggest other things I should check on the engine. The engine still runs, and in fact I was able to start it once off the flatbed tow truck, to pull it into my garage, running off the battery.


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## geeteeohguy (Feb 2, 2008)

As a retired mechanic with 42 years in the industry and thousands of cars and repairs, I have never seen this. Have seen seized pumps, leaking pumps, dissolved impellers, tossed fans, etc. but never this. Looks like the impellor came off the shaft and the shaft walked out, leveraging against the casting, breaking the nose off. I guess there's always a first time. 
I've worked on all makes and models from 1911 up to 2020 vintage and have never seen this. Always a first time, I guess. You will likely need the water pump divider plates as well. You'll know when you get the pump off.


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## Sick467 (Oct 29, 2019)

Just quit it...your gonna give me nightmares! That's some destruction...at least you still have a radiator and a hood. Those tend to get damaged when the fan goes rogue.


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## BLK69JUDGE (Jun 10, 2010)

non gm casting ....hmmmmmmmmm


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## PontiacJim (Dec 29, 2012)

I am going to say belt tension. The belt was pulling hard towards the driver's side looking at the way it busted out from the passenger side and rotated leaving the more complete casting on the driver's side.

As *BLK69JUDGE* pointed out, not a factory WP, so the casting may have been flawed/hairline right from the start and the belt tension just eventually added to it.

Could have been worse with a blade or 2 coming through the hood.


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## ragtopgoat (Sep 26, 2019)

I did forget to mention, the radiator (aftermarket Champion) is toast. It took a big hit from the fan once it was airborne. The hood did get clipped, leaving a very minor dimple that's visible on top. Nothing major though indeed and I feel pretty lucky.


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## CoveKid19 (Nov 18, 2021)

Ouch!!! First time I've seen something like that from a water pump.


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## BLK69JUDGE (Jun 10, 2010)

ok ,,,, I didnt think that missed the radiator ... damm sorry to see that
yah I am on my second FOSTERS barley pop as I was just towed home by AAA 65 miles
after having fuel pump issue in my 99 suburban
after stopping for more ice and pops
after salmon fishing this am ,,,
and while I re read this post....
maybe I am looking in a mirror ...
but
is the fan mounted backwards ???
on the waterpump ,,,, ???


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## lust4speed (Jul 5, 2019)

Wow, that sucks! I also have never seen this happen. I did have a bearing failure years ago but the bearing and shaft just traveled forward and dropped down which had enough angle to put the fan into the radiator.

Fan does look backwards, and I don't see a fan clutch? If no clutch, then the direct drive would have increased the carnage. My fan just impaled itself into the radiator and stopped spinning because the fan clutch slipped.


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## ragtopgoat (Sep 26, 2019)

lust4speed said:


> Wow, that sucks! I also have never seen this happen. I did have a bearing failure years ago but the bearing and shaft just traveled forward and dropped down which had enough angle to put the fan into the radiator.
> 
> Fan does look backwards, and I don't see a fan clutch? If no clutch, then the direct drive would have increased the carnage. My fan just impaled itself into the radiator and stopped spinning because the fan clutch slipped.


The fan wasn’t backwards, that I’m sure of. Probably the way it is sitting on my bench looks wrong. It doesn’t have a fan clutch. I’ve wondered if it should, or if that would be a good upgrade to make. It is a convertible car with no A/C, maybe that’s why there’s no clutch.


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## BLK69JUDGE (Jun 10, 2010)

so your saying the fan has not been off the water pump since the misshap ??

rivets on all my pontiac fans come in from the front and get hammered on the engine side.....
so I thought

my 67 hd gm fan like yours is stamped FRONT by the pump bolts ,,


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## armyadarkness (Dec 7, 2020)

Same thing happened to me, two years ago!

I only lost my fan and pump... Which is how I came to redo my entire cooling system.

I was at cruise on the interstate and I heard some ticking, then full-on metal nightmares. When I pulled off the road, the fan was in the steering box.

As near as I can tell, this ocurred because I was running an upgraded Powermaster alternator, as well. 

When the belt is tensioned to their spec, and/or enough to stop alternator squealing, it's simply more than a "parts house" water pump bearing can handle. At least, this is what happened to me.

What kind of water pump do you have?

When was the last time your cooling system was serviced?


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## ragtopgoat (Sep 26, 2019)

BLK69JUDGE said:


> so your saying the fan has not been off the water pump since the misshap ??
> 
> rivets on all my pontiac fans come in from the front and get hammered on the engine side.....
> so I thought
> ...


Until this morning, the fan was mounted to the water pump pulley, exactly how it was during the mishap. I've not heard that detail about the rivets until mentioned on this thread and never paid much attention to it. Now that I look closer at the fan after detaching it, I can see bolt imprints on both sides of it. I'd say whoever mounted it last didn't pay attention to the way it was installed. Not the first "attention to detail" that was not paid on this engine...


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## ragtopgoat (Sep 26, 2019)

armyadarkness said:


> Same thing happened to me, two years ago!
> 
> I only lost my fan and pump... Which is how I came to redo my entire cooling system.
> 
> ...


Same for the Powermaster alternator. Their instructions say you should have the belt tight enough that you can't turn the alt pulley with a wrench. That's pretty snug.
The engine cooling system is how it came to me when I bought this car in 2019. I don't know what water pump it is, I'll have to dig into to it more when I get it removed. The only cooling service that has been done was by me, when I replaced the lower water hose which was leaking when I bought the car. I replaced the hose, found the inlet pipe on the timing cover was heavily scarred with corrosion and sought some advice here at that time. Ended up fixing the inlet pipe with QuikSteel, new lower hose with a stainless spring and a full coolant flush. The cooling system has been airtight and never ran above 160 degrees.


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## Mine'sa66 (Oct 30, 2019)

I have seen similar, but only similar and very uncommon.
Mostly because I have 40 years in very high volume shops so every crazy thing has come by at least once.
That is pretty crazy....


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## geeteeohguy (Feb 2, 2008)

Strange that you have a clutch type of fan but no clutch. These cars came with clutch type fans and flex fans. Not fixed IIRC. Jim will chime in if I'm wrong. 
How long was your spacer? I have seen folks install spacers and hang their clutch waaaaay out there with the fan, and would expect an explosion like this. You're lucky your hood didn't take a hit.


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## geeteeohguy (Feb 2, 2008)

ragtopgoat said:


> Same for the Powermaster alternator. *Their instructions say you should have the belt tight enough that you can't turn the alt pulley with a wrench. That's pretty snug.*
> The engine cooling system is how it came to me when I bought this car in 2019. I don't know what water pump it is, I'll have to dig into to it more when I get it removed. The only cooling service that has been done was by me, when I replaced the lower water hose which was leaking when I bought the car. I replaced the hose, found the inlet pipe on the timing cover was heavily scarred with corrosion and sought some advice here at that time. Ended up fixing the inlet pipe with QuikSteel, new lower hose with a stainless spring and a full coolant flush. The cooling system has been airtight and never ran above 160 degrees.


As a former pro mechanic, I can say that the engineer/person who wrote this did not service vehicles for a living. This is an absolute falsehood and a guaranteed way to wear out bearings and cause other issues like we've just seen here. 
There are belt tension guages for those who don't have the proper 'feel'. I always tighten V belts so you can turn them 90 degrees at mid span with your finger but no further. If you can't get to 90 you are too tight.


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## armyadarkness (Dec 7, 2020)

ragtopgoat said:


> Same for the Powermaster alternator. Their instructions say you should have the belt tight enough that you can't turn the alt pulley with a wrench. That's pretty snug.
> The engine cooling system is how it came to me when I bought this car in 2019. I don't know what water pump it is, I'll have to dig into to it more when I get it removed. The only cooling service that has been done was by me, when I replaced the lower water hose which was leaking when I bought the car. I replaced the hose, found the inlet pipe on the timing cover was heavily scarred with corrosion and sought some advice here at that time. Ended up fixing the inlet pipe with QuikSteel, new lower hose with a stainless spring and a full coolant flush. The cooling system has been airtight and never ran above 160 degrees.


Yes. Whenever I explain the Powermaster tension procedure to folks, theyre always shocked.

So, if your coolant was good, then yes, just chalk it up to a cheap/ generic rebuilt water pump. Get yourself a good FlowKooler, so it doesnt ever happen again


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## armyadarkness (Dec 7, 2020)

geeteeohguy said:


> As a former pro mechanic, I can say that the engineer/person who wrote this did not service vehicles for a living. This is an absolute falsehood and a guaranteed way to wear out bearings and cause other issues like we've just seen here.
> There are belt tension guages for those who don't have the proper 'feel'. I always tighten V belts so you can turn them 90 degrees at mid span with your finger but no further. If you can't get to 90 you are too tight.


But it's absolutely the Powermaster procedure... and trust me, if you dont do it, your belt will squeal like CRAZY when you get on the gas!


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## armyadarkness (Dec 7, 2020)

If you run a Powermaster, it's critical to use a known quality water pump, with fresh antifreeze to keep it lubed


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## Baaad65 (Aug 29, 2019)

ragtopgoat said:


> Same for the Powermaster alternator. Their instructions say you should have the belt tight enough that you can't turn the alt pulley with a wrench. That's pretty snug.
> The engine cooling system is how it came to me when I bought this car in 2019. I don't know what water pump it is, I'll have to dig into to it more when I get it removed. The only cooling service that has been done was by me, when I replaced the lower water hose which was leaking when I bought the car. I replaced the hose, found the inlet pipe on the timing cover was heavily scarred with corrosion and sought some advice here at that time. Ended up fixing the inlet pipe with QuikSteel, new lower hose with a stainless spring and a full coolant flush. The cooling system has been airtight and never ran above 160 degrees.


I have a CVF 8 rib serpentine and couldn't get the squeal out on wot so I over tightened it and blew out the wp bearings, at least it was in the garage. But I found that when the motor is hot the belt gets tighter so if I have the the correct tension when cold it will be way to tight when hot so I have it set pretty loose when cold then it's perfect hot which is weird to me because I would have thought as it heats up it would stretch but it's opposite. Maybe it's the nature of that type of belt, do v belts do this?


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## ragtopgoat (Sep 26, 2019)

geeteeohguy said:


> Strange that you have a clutch type of fan but no clutch. These cars came with clutch type fans and flex fans. Not fixed IIRC. Jim will chime in if I'm wrong.
> How long was your spacer? I have seen folks install spacers and hang their clutch waaaaay out there with the fan, and would expect an explosion like this. You're lucky your hood didn't take a hit.


I would prefer to have a clutch type fan, so I'll look into that for the replacement. The spacer is 2". I've attached a picture, from a couple of years ago when the engine is running, which gives a pretty good view of the fan/spacer/pulley. You can see the fan is spaced pretty well in relation to the shroud. Again, this was how the car was set up when I acquired it, so I won't be surprised if it is not correct.


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## armyadarkness (Dec 7, 2020)

I would run a flex fan or as most of the purists will tell you, ditch the spacer and go clutch fan.


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## BLK69JUDGE (Jun 10, 2010)

the fan isnt stamped FRONT by the bolt holes ?? doesnt matter now anyways ....
Im surpised it cooled ...
that is NOT a clutch fan bolted to a spacer
they have way different bolt patterns
it looks to be the GM PONTIAC HD cooling NON AC cooling fan to me tough one to find
found on alot of 4 speed cars
spirited 4 speed driving often wears out the guts of clutch fans faster


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## Jared (Apr 19, 2013)

Hmmm. What I've learned here. Skip the Powermaster alternator when the time comes.


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## armyadarkness (Dec 7, 2020)

Jared said:


> Hmmm. What I've learned here. Skip the Powermaster alternator when the time comes.


Dont skip the brand, skip the high amps! No need for a 100 amp alt in a 55 year old car


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## Baaad65 (Aug 29, 2019)

armyadarkness said:


> Dont skip the brand, skip the high amps! No need for a 100 amp alt in a 55 year old car


Unless someone's car were to have let's say three electric fans, a 100w per channel amp, a subwoofer, electric gauges, power antenna, rear defroster, MSD ignition, electric cutouts, AFR meter and two phone charging outlets... oh and then throw on the high beams...then someone's car would probably have a 140 amp alt


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## armyadarkness (Dec 7, 2020)

Baaad65 said:


> Unless someone's car were to have let's say three electric fans, a 100w per channel amp, a subwoofer, electric gauges, power antenna, rear defroster, MSD ignition, electric cutouts, AFR meter and two phone charging outlets... oh and then throw on the high beams...then someone's car would probably have a 140 amp alt


Obviously its a mathematical question and answer. Yes, all of those accessories would require a lot more amps, but only if you were using them all at once!

A house is the same way.

I run a welding shop and music studio off a 100 amp service... and I suspect that there arent many other members in here who are running four, 6-foot-tall, 500 watt, vacuum tube, bass amplifiers at the same time... or welding 3/8" aluminum at 250 amps, while they're doing laundry.

And... keep in mind that modern electronics are much more efficient than the old days... so you could likely run a power amp, ignition, and four LED headlights, off less power than a 67 AM radio.

Regardless, you bring up a good point... just like carburetors, there's no need to guess. Do the math, and get the alternator that you need, otherwise you're wasting horsepower for no reason.


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## Duff (Jan 12, 2020)

I don't run a lot of added accessories, so the factory 37 or 55 amp has always worked for me.


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## Baaad65 (Aug 29, 2019)

armyadarkness said:


> Obviously its a mathematical question and answer. Yes, all of those accessories would require a lot more amps, but only if you were using them all at once!
> 
> A house is the same way.
> 
> ...


Oh I run everything all the time, it's like the Wonka Mobile


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## BearGFR (Aug 25, 2008)

armyadarkness said:


> Dont skip the brand, skip the high amps! No need for a 100 amp alt in a 55 year old car


...Unless you've added things like electric cooling fans (mine pull 30 amps - each), "thumper" stereo, etc.

Bear


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## armyadarkness (Dec 7, 2020)

BearGFR said:


> mine pull 30 amps - each


Man that has to suck up power! So your alternator is putting as much drag on the engine, as a fan, at this point?


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## geeteeohguy (Feb 2, 2008)

armyadarkness said:


> If you run a Powermaster, it's critical to use a known quality water pump, with fresh antifreeze to keep it lubed


I like my radios with tubes and civil defense Delta symbols on them. If I ran a 100 amp alternator that required so much belt tension that it damaged other components, I would switch to a serpentine system or bigger pulleys. But, like some, I only need 35-40 amps in all my old cars. Been working for my for decades. My Corvette still runs a generator.


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## geeteeohguy (Feb 2, 2008)

armyadarkness said:


> But it's absolutely the Powermaster procedure... and trust me, if you dont do it, your belt will squeal like CRAZY when you get on the gas!
> 
> View attachment 157796


I mis-read this a bit, or mis-interpreted. I thought it meant that you would not be able to turn the NUT and the pulley because the belt was so tight. Here, it just wants you to have it snug enough so it doesn't slip when you turn the pulley. That's not THAT tight. But it would be easy to overdo if you don't have _The Magic Touch,_ as the late, great, Bobby Fuller put it.


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## ragtopgoat (Sep 26, 2019)

armyadarkness said:


> I would run a flex fan or as most of the purists will tell you, ditch the spacer and go clutch fan.


I am going to go with a fan/clutch and after looking at Ames and reading some other threads on the forum, the consensus appears to be, to with a Hayden clutch and a 19.5" stock fan. My car is a non-A/C car, so the radiator is a 15.5" core, which the stock shroud and fan that would fit would be an 18" fan. I don't plan to modify the car to take a larger 17.5" core, so I assume I need to stick with the smaller 18" fan and matching shroud. Or can I get away with fitting the larger shroud with the 19.5" fan? I am not trying to solve a cooling problem, so I would think that the 15.5" core sized shroud and 18" clutch fan should be enough.

Any input would be appreciated.


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## geeteeohguy (Feb 2, 2008)

I'm running a 19.5" Pontiac AC fan (1970 vintage) with a newer Hayden clutch and ended up cobbling together an aftermarket plastic shroud since my original shroud would not fit. It works fine, and it's amazing how much bigger the 19.5 is compared to the stock 18. It's only an inch and a half, but it looks much, much larger. I'll take a photo and post it. My car has the original 4 row (tripower) HD 15.5 inch core, so same as yours, fit-wise.


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## 67ventwindow (Mar 3, 2020)

You need the 100amp. Never know when you need to MacGyver weld road side using your jumper cables. 

It can happen!


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## lust4speed (Jul 5, 2019)

I've done two A-bodies where we installed the larger shroud and the 19.5" fan behind the non-AC 15-1/2" core radiator. Little tricky and it gets a little scary to take a new shroud and cut a big hole for the lower radiator hose to pass through. Much less work if your top hose is on the driver's side and bottom is on the passenger because at least then the top of the shroud sets properly in place without surgery. Definitely more cooling but you have to work for it. A properly set up smaller non-AC 7-blade fan and shroud should be plenty to maintain cooling unless you add an aftermarket AC system.

Part of your problem could have been the fan speed achieved without the fan clutch. You have (had?) a very nice set of over-driven pulleys but this allowed the fan to really haul. The fan clutch by design disengages the fan at a shaft speed of around 4400 to 4600 RPM. Basically the silicone fluid is pulled away from the shaft at that speed limiting any further speed increase. If your bottom pulley was 8" and top was 6" then your over drive ratio is about 1.33:1. So shifting at 6,000 would have the fan turning 8,000 RPM. It wouldn't be instant failure but the additional direct drive speed could have eventually led to the water pump failure over time.


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## Jared (Apr 19, 2013)

Baaad65 said:


> Unless someone's car were to have let's say three electric fans, a 100w per channel amp, a subwoofer, electric gauges, power antenna, rear defroster, MSD ignition, electric cutouts, AFR meter and two phone charging outlets... oh and then throw on the high beams...then someone's car would probably have a 140 amp alt


Wait a minute. You have all of that stuff in your car? I don't even have a radio in mine.


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## Baaad65 (Aug 29, 2019)

Jared said:


> Wait a minute. You have all of that stuff in your car? I don't even have a radio in mine.


Yup.


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## geeteeohguy (Feb 2, 2008)

Jared said:


> Wait a minute. You have all of that stuff in your car? I don't even have a radio in mine.


I can see you didn't see the tach and multi-meter mounted under the hood of mine! LOL....the guy who owned the car before me installed it with a bunch of other stuff in the '70's. You can tune the car on the side of the road.


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## BLK69JUDGE (Jun 10, 2010)

thats cool ..... having a dwell meter mounted under the hood ...

I still dont know how his engine cooled in the summer with the fan on backwards....


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## Baaad65 (Aug 29, 2019)

geeteeohguy said:


> I can see you didn't see the tach and multi-meter mounted under the hood of mine! LOL....the guy who owned the car before me installed it with a bunch of other stuff in the '70's. You can tune the car on the side of the road.


I was wondering about that stuff but forgot to ask


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## armyadarkness (Dec 7, 2020)

BLK69JUDGE said:


> I still dont know how his engine cooled in the summer with the fan on backwards....


I presume that the car went backwards once the RPMs were up?.


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## Jared (Apr 19, 2013)

geeteeohguy said:


> I can see you didn't see the tach and multi-meter mounted under the hood of mine! LOL....the guy who owned the car before me installed it with a bunch of other stuff in the '70's. You can tune the car on the side of the road.


I saw it. I couldn't figure out what was going on though. Multi meter set up may be older than I am. Makes you wonder about the past owner.


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## geeteeohguy (Feb 2, 2008)

Past owner worked for Pacific Bell Telephone. Car has a lot of underhood wiring mods plus chrome and Day Two stuff, some of which I have removed over the years. All done in the 1970's. I've had the car for 40 years and have never had any issue with the mods, was going to remove them 20 years ago, but now, they are part of the car's story. If the next owner wants to go to stock, he or she can. For me, it's Day Two.


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## CoveKid19 (Nov 18, 2021)

Some food for thought. Looking at the OP's pictures again, I see the WP shaft and bearing housing have separated. That housing is pressed/crimped, if I recall correctly, so I wonder if the shaft was walking for/aft and threw a belt which started the chain of events. If it were just the pump casting that failed due to belt tension, I think the shaft and bearings should have stayed together. Here's a pic of a NOS GM water-pump rebuild kit I've had for 40 years and you can see how the bearing housing comes as part of the shaft.


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## ragtopgoat (Sep 26, 2019)

armyadarkness said:


> I presume that the car went backwards once the RPMs were up?.


I feel like I need to defend myself here, that I was not driving this car around with the fan pushing air instead of pulling it. Here is a picture from two years ago that I took of the belts, that shows the fan. You can see the blades were oriented such that in the clockwise rotation (looking from the front of the car) they were pulling air through the radiator. The car never ran hot, in traffic on hot summer days.


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## armyadarkness (Dec 7, 2020)

ragtopgoat said:


> I feel like I need to defend myself here, that I was not driving this car around with the fan pushing air instead of pulling it. Here is a picture from two years ago that I took of the belts, that shows the fan. You can see the blades were oriented such that in the clockwise rotation (looking from the front of the car) they were pulling air through the radiator. The car never ran hot, in traffic on hot summer days.
> 
> View attachment 157877


No need to defend yourself at all! It's simply the way the my Abby Normal brain works... I see comedy in everything, so when someone said your fan was on backwards, I imagined the Little Rascals go kart.

I already mentioned what I thought your issue was... and trust me, if my life depended on spotting fan orientation, you guys would all be at my funeral now.


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## geeteeohguy (Feb 2, 2008)

I just went out to the shop and looked at my original '67 GTO clutch and fan hanging on the wall. The bent tips and orientation are exactly the same as ragtop's, except mine has a clutch on the front of it. Haven't run it for 30 years, as the '69 Cadillac flex fan cools better. (probably because of a bad clutch on the oe fan)


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## BLK69JUDGE (Jun 10, 2010)

The hub or center of the fan s arms go on the BACK of the blade not the front with the round outward curve of blades face towards radiator your arch of the blade face in your pictures is towards the engine.
It doesn’t matter now anyway
Just my observation from working on
Gm Abody s for 45 years


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## ragtopgoat (Sep 26, 2019)

BLK69JUDGE said:


> The hub or center of the fan s arms go on the BACK of the blade not the front with the round outward curve of blades face towards radiator your arch of the blade face in your pictures is towards the engine.
> It doesn’t matter now anyway
> Just my observation from working on
> Gm Abody s for 45 years


That’s good to know and I will add that to my knowledge base. I will be going with a clutch fan to replace it, based on recommendations on this thread and others.


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## geeteeohguy (Feb 2, 2008)

BLK69JUDGE said:


> The hub or center of the fan s arms go on the BACK of the blade not the front with the round outward curve of blades face towards radiator your arch of the blade face in your pictures is towards the engine.
> It doesn’t matter now anyway
> Just my observation from working on
> Gm Abody s for 45 years


Good catch. Even with my original fan, which shows what you are talking about, I did not realize the OP's fan tips were pointed towards the engine and not the radiator, as my fan shows.


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## Jared (Apr 19, 2013)

ragtopgoat said:


> That’s good to know and I will add that to my knowledge base. I will be going with a clutch fan to replace it, based on recommendations on this thread and others.


Fan clutch is the way to go. I'm running a stock style fan and clutch on mine and I'm pushing close to 500 hp. Mine runs at 180F all the time even when it's over 90 outside.


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## Herding Goats (Sep 16, 2017)

Firstly, @ragtopgoat sorry to see this happen and glad you're working to get this Pontiac back on the road. Saw this thread the other day and mentioned it to a good friend and better old time mechanic. He said check the motor mounts. Idea being if the motor mounts are weak they could allow the fan to come in contact with something and let loose. He had a horrifying story about a straight six Chrysler that sent a fan through the hood and into someone's face when a motor mount failed. Probably not a motor mount from what has been discussed here, but just sharing the experience and idea for all to keep in mind.


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## geeteeohguy (Feb 2, 2008)

In 1988 I bought a 1937 Chrysler Imperial business coupe with a straight 8. I was driving it on the freeway at 60 mph in overdrive and it threw a fan blade right into the upper radiator tank. Sounded like the world came to an end and the car vibrated like a washing machine with a bowling ball in it. Had the radiator repaired and got a new fan at Seeno's auto wrecking. That fan was solid stamped steel and came apart with zero warning. Scary. Great point on the motor mounts!


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## ragtopgoat (Sep 26, 2019)

Herding Goats said:


> Firstly, @ragtopgoat sorry to see this happen and glad you're working to get this Pontiac back on the road. Saw this thread the other day and mentioned it to a good friend and better old time mechanic. He said check the motor mounts. Idea being if the motor mounts are weak they could allow the fan to come in contact with something and let loose. He had a horrifying story about a straight six Chrysler that sent a fan through the hood and into someone's face when a motor mount failed. Probably not a motor mount from what has been discussed here, but just sharing the experience and idea for all to keep in mind.


Good call out on the motor mounts, worth a check. Is there a good method of verifying them beyond a visual inspection of the condition of the rubber insulator? Look for evidence of movement beyond normal torque-twist?


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## geeteeohguy (Feb 2, 2008)

You can gun the engine from under the hood in park or neutral and look at it. If you have a broken mount it will move a LOT. If an auto car, put your foot on the brake, put it in gear, and give it a bit of gas and watch for it to lift out of the mount on the driver's side. 99% of the time, it's the driver's side mount that fails.


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## CoveKid19 (Nov 18, 2021)

A fan pulls air through the radiator regardless of which way it's attached to the hub. Only reversing the direction of rotation will make the air push forward toward the radiator. That said, the OP's fan is, or was in this case, attached incorrectly and not pulling air efficiently, though it was pulling.


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## BLK69JUDGE (Jun 10, 2010)

“a fan pulls air thru the radiator no matter what way it’s attached to the hub “

Huh ..,? I ain’t no science tist but ….
I disagree. If on backwards Seems the back/tail edge of the blade is cutting air turning same direction
And would be totally inefficient 
may even cause a harmonic vibration
At higher rpm fighting itself

nuf said from me.


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## BearGFR (Aug 25, 2008)

BLK69JUDGE said:


> “a fan pulls air thru the radiator no matter what way it’s attached to the hub “
> 
> Huh ..,? I ain’t no science tist but ….
> I disagree. If on backwards Seems the back/tail edge of the blade is cutting air turning same direction



Seems like it at first, doesn't it? But think about it.
Here's what the 'end' of a fan blade looks like as seen when you're looking at the 'end' of it. (The red is the hub, the black is the shaft, the blue is the fan blade itself).











Now, here's the exact same image, rotated 180-degrees with no other changes, as if it was mounted "backwards".









Notice how the blade still 'slants' in the same direction? So yeah, if you flip a fan over 'backwards' it will still pull air in the same direction.

Bear


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## Machinest-guy (Jul 19, 2019)

I've seen a few of these failures. 

Diagnosis led to a pretty clear path to failure. The engine was jacked up to either change a mount or access a leaking core plug. The mechanic was too lazy to remove the fan so when the engine was raised it bent a few blades against the shroud. The bent fan blades caused a harmonic vibration which failed the water pump bearing / casting / shaft / clutch fan / or fan. It was a race to which part failed completely first. BUT ALL WERE DAMAGED TO SOME EXTENT AND SHOULD BE SCRAPPED. 

The amount of power a V-belt can transmit is determined by the belt cross section and length of contact patch with the pulley. The length of contact patch is determined by the wrap angle around the pulley. The wrap angle can be modified by changing pulley size. If belts are over tightened then the various shaft or pulley bearings will be overloaded and fail prematurely. The procedure mentioned of tightening until no slippage occurs isn't the best procedure, but can eliminate a squeal or slipping belt for some unknown period of time before failure. And sometimes can shift the economic costs of failure from the alternator company to the belt or installer. 

The acceptable procedure is to install double sheave pulleys - as done on many other models - instead of over tightening a single belt. 

For our old Pontiac pulley sets there are two easy paths to eliminate this issue. One) If dual belts wrap off the crank pulley and only one goes to the top side of the alternator then get a longer belt and double sheave alternator pulley so both make that path. Two) Find a generic pulley set from an A/C car that has double sheave pulleys to the compressor then change pulleys as required to run whatever options the car has. 

The fan blades should have no more than 1/8th inch fore - aft difference when the fan is rotated freely without any belts. And the fan should have all blades within 1/8 inch in overall diameter blade to blade. IF THEY DON'T THEN STRAIGHTEN THE FAN, TRIM THE TIPS, OR REPLACE IT. Even with these specifications met a fan can still be out of balance dynamically. GM balanced some fans from the factory. They can be identified by a weight drilled and riveted to the blade on the blades cord center-line about two inches out from the hub center hole. Think Cadillac.

Sorry to hear you had this issue, but as many have said here - you had good luck with the hood and it didn't blow the back out of the timing cover and fill your crankcase with coolant as case fragments broke your timing chain......

One last thing to check after this sort of failure is the crankshaft snout run out. The crank snout should have no more than .003 run out. Zero is really really nice. If the crank is bent it will add a little tug to the belt every rotation causing shortened accessory and accessory drive component life. 

Ladd


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## Baaad65 (Aug 29, 2019)

Machinest-guy said:


> I've seen a few of these failures.
> 
> Diagnosis led to a pretty clear path to failure. The engine was jacked up to either change a mount or access a leaking core plug. The mechanic was too lazy to remove the fan so when the engine was raised it bent a few blades against the shroud. The bent fan blades caused a harmonic vibration which failed the water pump bearing / casting / shaft / clutch fan / or fan. It was a race to which part failed completely first. BUT ALL WERE DAMAGED TO SOME EXTENT AND SHOULD BE SCRAPPED.
> 
> ...


So I asked this in a previous post on this thread but didn't get an answer, why does my 8 rib serpentine belt get tighter with heat? I would have thought the heat would loosen it, so I have to have it pretty loose when cold then it's just right when the motor is around 180°. It's a Gates RPM belt. Do V belts do this?


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## geeteeohguy (Feb 2, 2008)

Expansion of the metal pulleys from the heat? Wouldn't take much. Machinist Guy's post is very informative, and makes total sense if you think about it. Think of AC systems in the old days on Chrysler products and others that required a 'matched set' of two belts to run a big York AC compressor. Kind of like running dual tires on the back of a HD truck to handle the load without straining one lone component. 
I heat and cool bushings, bearing races, etc. all the time that are interference fit and it makes installation a lot easier. Even .001-.002" goes a long way.


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## Baaad65 (Aug 29, 2019)

geeteeohguy said:


> Expansion of the metal pulleys from the heat? Wouldn't take much. Machinist Guy's post is very informative, and makes total sense if you think about it. Think of AC systems in the old days on Chrysler products and others that required a 'matched set' of two belts to run a big York AC compressor. Kind of like running dual tires on the back of a HD truck to handle the load without straining one lone component.
> I heat and cool bushings, bearing races, etc. all the time that are interference fit and it makes installation a lot easier. Even .001-.002" goes a long way.


Maybe but that would be a lot of expansion and they are aluminum pulleys so does that mean more or less over steel?


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## Sick467 (Oct 29, 2019)

@Baaad65, I cannot explain why a belt would get tighter with the added heat with confidnce. The pulleys would grow with added heat, but very very little. Compare this to the growth of the belt and I would think the growth of the pulleys would be negligible...meaning the belt growth would more than compensate for the pulley growth.

I'm not swift enough with heat transfer to use cylindrical examples, but I can easily use simple lengths of material to demonstrate how steel vs aluminum vs rubber would expand after heat is applied...

Assume you start the car at 30° F and it tops out at 200° F. That's a 170° F change (ΔT).

The coefficients of expansion for steel, aluminum, & rubber (generically speaking) are...

Steel - 0.0000065 in/(in°F)
Aluminum - 0.000012 in/(in°F)
Rubber - 0.00015 in/(in°F)

Given the same change in temperature (ΔT) steel expands half as much as aluminum, while rubber expands 6 times that of aluminum.

Here are some simple calculations using....(the length of material (L), the change in temp (ΔT), & the coefficients of expansion (CTE) ... L x ΔT x CTE...

Given a 10 inch long piece of steel and aluminum materials and a longer rubber belt length...

Steel would expand - 10in x 170°F x 0.0000065 in/(in°F) = 0.011 inches
Aluminum would expand - 10in x 170°F x 0.000012 in/(in°F) = 0.020 inches
Rubber - 10in x 170°F x 0.00015 in/(in°F) = 0.26 inches

Your rubber belt will not likely have the same ΔT as the pulleys since it travels through the air so much and cools better, so I will use a much smaller ΔT and a much longer length...

Rubber - 25in x 85°F x 0.00015 in/(in°F) = 0.32 inches

I know that the above mumbo-jumbo does not come close to what your system is witnessing, but it does show that rubber expands a LOT more than the steel or aluminum. This leads me to think that a belt would get more loose with the added heat just as you have thought.

There would also be expansion in the block and heads that would move the pulleys farther apart, but were still talking thousandths of an inch.

I can't explain how your belt is getting tighter without thinking that the thermal expansion of the belt is a LOT less than my assumption. IF the belt does not grow in length with heat (or extremely little) which could be by design, the pulleys will which makes their diameter a bit larger, and the block and heads will grow making the distance between the pulleys larger. In affect, larger pulley diameters and further center distances want a longer belt.

I could also have to do with the thermal growth of the belt with respect to width and height (maybe it does not grow much in length, but does otherwise). If it gets wider, it may walk up and out of the pulley a bit...adding to the pulley diameter growth. Same thing if it gets thicker...it may try to walk up and out of the cogs in the pulley.

Just spit-balling, thanks for making my head hurt.


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## Baaad65 (Aug 29, 2019)

Ha ha that's good stuff and now I'm a little less dumb, I could call CVF or Gates but I just thought after the belt is broke in it should stay the same and I have checked the tensioner nuts and they are tight. Who knows but I just keep an eye on it every drive, I would rather have it looser at first and not blow out the WP bearings...again, thanks.


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## z man (Jun 20, 2010)

Baaad65 said:


> Ha ha that's good stuff and now I'm a little less dumb, I could call CVF or Gates but I just thought after the belt is broke in it should stay the same and I have checked the tensioner nuts and they are tight. Who knows but I just keep an eye on it every drive, I would rather have it looser at first and not blow out the WP bearings...again, thanks.





Baaad65 said:


> Ha ha that's good stuff and now I'm a little less dumb, I could call CVF or Gates but I just thought after the belt is broke in it should stay the same and I have checked the tensioner nuts and they are tight. Who knows but I just keep an eye on it every drive, I would rather have it looser at first and not blow out the WP bearings...again, thanks.


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## z man (Jun 20, 2010)

please cut a chain to fasten between your engine block and frame/ upper arm on drivers side. Leave one link extra. This will prevent any lifting of engine if motor mount cracks. Ask me how I know. The accelerator cable doesn’t help.


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## Baaad65 (Aug 29, 2019)

That doesn't sound good, I have new motor mounts going in this winter.


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## ragtopgoat (Sep 26, 2019)

Sick467 said:


> @Baaad65, I cannot explain why a belt would get tighter with the added heat with confidnce. The pulleys would grow with added heat, but very very little. Compare this to the growth of the belt and I would think the growth of the pulleys would be negligible...meaning the belt growth would more than compensate for the pulley growth.
> 
> I'm not swift enough with heat transfer to use cylindrical examples, but I can easily use simple lengths of material to demonstrate how steel vs aluminum vs rubber would expand after heat is applied...
> 
> ...


I would think that the aramid fibers in the v-belts would help to prevent the belts from lengthening when warm. Expanding thickness-wise, sure, but probably not length.


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## Machinest-guy (Jul 19, 2019)

Assuming The belt expands when heated might not be true. A quote from a Gates engineer follows, 

The belt uses a Kevlar cord as its back bone. Kevlar has a backward coefficient of thermal expansion. Gates confirms that the molded belt assembly changes length in sink with plain Kevlar. Therefore, when my machine sees 40 below zero the steel frame will shrink (center to center dist of drive)and the belt will grown in length. From first calculations this will remove all tension from the belt. Gates says a cog belt without tension will probably fail immediately. They also say they do not have a problem in real applications with temperature driven tension changes. 

This link to the Gates belt engineering data site is informative without getting too much on target for this exact question. 



https://ww2.gates.com/IF/facts/documents/Gf000273.pdf


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## Jetzster (Jan 18, 2020)

Baaad65 said:


> That doesn't sound good, I have new motor mounts going in this winter.
> View attachment 157991
> View attachment 157992
> View attachment 157993


Looks like fun to me Baaad🤨are they a preferred mount in some way?


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## Baaad65 (Aug 29, 2019)

I don't think it's going to be fun, the drivers side has a locking screw so I guess they're a hybrid of a solid and a stock rubber mount.


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## ragtopgoat (Sep 26, 2019)

Update: I am taking this opportunity to replace not only the radiator, fan and water pump. I’m also replacing the timing cover. Which now that I have that off, I’m looking at the timing chain and sprockets, which I have no idea how old they are. This video linked here, shows the slack in the chain (sorry about the music). It is very loose on the right side, tighter on the left side. Is this the right way to check it? It looks like it’s time to replace it to me.

Same question for the harmonic balancer. I don’t see anything obviously wrong with it, but maybe prudent to replace it given that I have no idea of its history. Picture attached of the HB for reference.


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## PontiacJim (Dec 29, 2012)

ragtopgoat said:


> Update: I am taking this opportunity to replace not only the radiator, fan and water pump. I’m also replacing the timing cover. Which now that I have that off, I’m looking at the timing chain and sprockets, which I have no idea how old they are. This video linked here, shows the slack in the chain (sorry about the music). It is very loose on the right side, tighter on the left side. Is this the right way to check it? It looks like it’s time to replace it to me.
> 
> Same question for the harmonic balancer. I don’t see anything obviously wrong with it, but maybe prudent to replace it given that I have no idea of its history. Picture attached of the HB for reference.
> 
> View attachment 158044


You will have slack on one side and not the other due to the rotational pull on the chain - clockwise. However, the chain looks a bit on the loose side and because you have the timing cover off, cheap enough to install a new gear set and chain and not have to worry about it.

If that is your HB, get a new one as that one will cause vibration and that's not a good thing.


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## ragtopgoat (Sep 26, 2019)

PontiacJim said:


> You will have slack on one side and not the other due to the rotational pull on the chain - clockwise. However, the chain looks a bit on the loose side and because you have the timing cover off, cheap enough to install a new gear set and chain and not have to worry about it.
> 
> If that is your HB, get a new one as that one will cause vibration and that's not a good thing.


That is my HB, I figured it was better to replace it. Is it a simple part swap with a new HB, or do I need to take the old and new HBs to a machine shop and get the new one balanced to match the old one?


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## Jared (Apr 19, 2013)

X2 on replacing that. It looks a bit rough. Pontiac used a damper, not a a balancer. No need to have it balanced, just get a new one.


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## PontiacJim (Dec 29, 2012)

ragtopgoat said:


> That is my HB, I figured it was better to replace it. Is it a simple part swap with a new HB, or do I need to take the old and new HBs to a machine shop and get the new one balanced to match the old one?


As *Jared *said, everyone calls it a "harmonic balancer" but Jared just had to get technical - it's a dampener. LOL Kinda like we used to call the 1970-73 big police Fury chase cars "Interceptors." Technically, that was a Ford name and Plymouth was called a "Pursuit." Interceptor/Pursuit, hell, when the blue light came on behind you it was just plain "ticket." LOL

Pontiac dampers are a slip fit, unlike chevey and others that are press fit and you use a tool to get them off and on. MOST IMPORTANT is to torque that big bolt to 160 Ft Lbs or if it vibrates loose, it can crack the inside lip and go into the timing chain and you got another problem on your hands.


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## geeteeohguy (Feb 2, 2008)

X3 on the chain and damper. Chain is not worn out, but is stretched a bit, which will retard the cam timing and soften performance. The damper rubber is rotting and


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