# Running Hot



## Jim (Oct 30, 2008)

Hey Guys,

I read some of the post about overheating but couldn't find the one I was looking for. My 67 runs fine in town but on the highway get's up to 220 to 230.

Clearly this is with some aftermarker cheap gauges. I had the readiator taken apart and rodded and cleaned, I flushed the system, etc.

I don't have a shroud but didn't think that should matter if it's getting hot on the highway.

What's the problem???

Jim :cheers


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## jetstang (Nov 5, 2008)

No shroud would make it get hot in traffic. Odd problem, change your thermostat to a 160/180 degree for the summer, maybe a low flow problem with RPM. It has enough flow for low RPM cruise, but not high speed. Also, make sure you have fresh oil, thicken it to 20W50. Oil cools the engine, old or thin oil doesn't dissipate heat well.


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## GTO JUDGE (May 14, 2005)

I have a 180* thermostat. It reads about 189-190 when driving, when I idle it gets up to 200-205 as soon as I get going again it goes back to 190 or so. I am using wetter water and the radiator has a shroud along with the pressure release locking radiator cap. I was thinking maybe changing the thermostat to a 160* one this winter. I am using 20W50 oil too.

According to the shop manual.... the 190* thermostat which the car calls for, the range goes to about 232* I think that's a bit hot.


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## 05GTO (Oct 6, 2004)

If there is more than 3" between the fan blades and the radiator try a spacer to move the fan closer to the radiator. Fixed my 66 overheating problem,

Mr. Gasket, PONTIAC - summitracing.com


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## geeteeohguy (Feb 2, 2008)

Run a 160 'stat, water wetter, and know that '67 Pontiac 400's in particular will run 210-215 on a hot day. Don't worry about it unless it's spitting out coolant or gets above 235 degrees or so.


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## auburnconsulting (Nov 3, 2008)

sounds like coolant flow problem. do you have formed rad hoses? old style water pump? do you even have a thermostat in it? if not you should have at least a thermo body in it , you need a restriction to allow coolant to absorb heat. add shroud. you could even seal the edges of the rad to the core support. that way all air entering engine compartment has to go through rad. the air would normaly go around first, path of least resistence. try all low cost items first. water wetter and 160 thermo.


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## NorcalPoncho (Jul 14, 2009)

Hi Guys,

I have just installed ceramic-coated 2.5" intake manifolds from Performance Years on my 1968 GTO motor, and ran it around town and on the highway for the first time last night. The engine got really hot, and took over three hours to cool to the point where it could be touched. 

I know that ceramic-coating will keep heat in the engine, but do I have to do something different now to keep my engine cool? Is this normal?


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## Dave67 (Jan 12, 2011)

*67 running very hot in Ft Worth heat wave*

I too am having problems with over heating.

Here are the particulars
-67 GTO
-Stock 335 HP 400 CID
-Aftermarket Classic Air A/C Unit
-180 thermostat (tested in water with digital thermometer)
-Aluminum Radiator (small size not the larger one used on AC cars)
- Running 10-40 pure synthetic (was recommended I stick 
w/ straight 30 weight)
-Fan Shroud (does not fit tight up against radiator about 1/2 gap between
radiator and shroud)
-7 Blade fan (1/2 in shroud 1/2 out of shroud) 
-After market gages (seem fairly consistent with IR reading thermometer)
- When parked after heating up will spit a little coolant out of release
lever radiator cap 

Runs 190 to 200 at 65-75 MPH on 106 degree day
Drop below 60 mph temp rises quickly
In Traffic or at a drive through can hit 235 (according to gage)

If car is hot and I floor it to where it kicks in passing gear, even though it is pushing hard, it cools down.

Would a 4 core radiator do better than the Aluminum radiator?

Does anyone run supplamental electric fans on 60's GTOs?

Any other suggestions?


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## BearGFR (Aug 25, 2008)

Hi Dave - how are you liking your Classic Air system? I'm putting one in my 69, but it's not "on the road" yet.

Some questions on your cooling system...
1) Are you running a fan clutch (and sure that it's good if you are)?
2) Did you adjust the 'clearance' on the plate behind the water pump impeller? I'm told the trick here is to lay the plate on the back of the pump with no gasket in place, "work" the plate with a hammer until it just barely touches the impeller, then when you install everything with the gasket in place the clearance will be where it needs to be for best cooling. 
3) Are you sure the pump drive belt(s) don't slip?

From your description, it sort of sounds like a fan related problem as if it's not moving enough air at lower speeds. (Fan clutch?) You could try sealing that 1/2" gap, perhaps with some of that metalized aluminum tape (the good stuff) to make sure your fan is pulling air through the radiator instead of around it.

Bear


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## Dave67 (Jan 12, 2011)

BearGFR said:


> Hi Dave - how are you liking your Classic Air system? I'm putting one in my 69, but it's not "on the road" yet.
> 
> Some questions on your cooling system...
> 1) Are you running a fan clutch (and sure that it's good if you are)?
> ...


Bear,
I like the Classic Auto Air just fine. I have a little leak I can't pin down so I have some dye in it to see if I can locate it. I did get the chrome and braided hoses kit. It looks great.

I have enough air leaks in the car that when tooling down the road, it is hard to keep the car cool in this weather but the AC is blowing cold air. Paul up at Technicare in Dallas does some mechanical work for me (he is great with these old cars) Anyway he thinks the condenser is too small since it does not cover the radiator a air will likely want to move around it instead of through it. I spoke to classic air about it and they said it is fine and to make sure to get the charge right. That is critical and when it is right the AC cools fine. I don't think it contributes much to the over heating. If I turn it off, the temp needle barely moves if at all.

It is a clutch fan and a brand new clutch. I did a newspaper test where I tried to stop the fan with a rolled newspaper - I could not even slow it down when it was engaged so I am guessing it is ok.

I have not pulled the waterpump, that may be worth looking at.

The belts are new and fine - no slippage there.

Thanks for the suggestions.


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## geeteeohguy (Feb 2, 2008)

Dave, 10/40 oil is fine for your car. What Bear said about the other stuff. You are not pulling enough air through the radiator core at slow speeds to effectively cool. Too small a radiator would result in hot temps at all times, not just in town. My first order of business would to get the air gaps out of the fan shroud. You also need to check your carburetion, as it could be a little lean (it cools down when you dump fuel when you get on it). Also, check that your ignition timing is where it should be: 6 degrees BTDC base timing with the vac. advance hose disconnected and plugged when you check. Then, re-install the vac. hose. You should be running manifold vacuum to the advance, not ported vacuum. Manifold vacuum will help it run cooler in traffic, and it's how the car was originally set up. Good luck.


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## Eric Animal (Oct 28, 2007)

the shroud should be 'sealed to the radiator. There are also flaps that seal to the radiator on an A/C car. These force the air entering the grill/bumper area to flow through the radiator, not around it.Check your water pump plates for proper clearance....you might want to run a smaller diameter water pump pulley (6").....E


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