Possible causes for GTOs overheating - Pontiac GTO Forum
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post #1 of 116 (permalink) Old 01-25-2008, 10:07 PM Thread Starter
 
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Possible causes for GTOs overheating

All,

I read a few posts about people having overheating problems.

I have a shop in my area that specializes in old pontiacs, specifically GTOs. The owner has been racing GTOs for over 35 years. So I asked him what the most common problems could be and here's his responses:

1. Some aftermarket water pumps have the impeller spaced further away from the plate. Too much space between the impeller and the plate doesn't allow the water to be pumped through the engine properly. The water just cavitates at the water pump and doesn't get sent through the engine.
2. Defective thermostat (very common, just happened to me not long ago) If the thermostat is not opening all the way or not opening at all, the car will definetly overheat. It may also overheat if stuck open, but usually the indication is the heater will not blow out hot air.
3. Retarding the timing to stop engine knock and pinging.
4. Clogged water passages or radiator....common sense.
5. Defective fan clutch. (I've also had this problem)
6. Oversize pully/s which makes the water pump turn slower.
7. Missing radiator filler panel. (if applicable )
8. Missing raidator shroud.
9. Lose/worn belts.
10. Defective/wore out water pump.
11. Driving in Southern California during fire season!

Hope these tips may help someone out.

Dale
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post #2 of 116 (permalink) Old 01-25-2008, 10:54 PM
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Good information!

Randy


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post #3 of 116 (permalink) Old 01-26-2008, 12:53 AM
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post #4 of 116 (permalink) Old 01-28-2008, 06:15 PM
 
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Garage
#12 Constant heavy throttle application !



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post #5 of 116 (permalink) Old 01-29-2008, 01:47 AM Thread Starter
 
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I forgot.....
#13 Letting wife drive car......No water.
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post #6 of 116 (permalink) Old 02-23-2008, 10:53 PM
 
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When I lived back in NY there was a guy named Nunzi in Bklyn, who was a guru and big racer of pontiacs. Had a very popular garage. He was in the game from day one and I had the same dilema in the eary 80's. He explained everything on your list and added that these cars ran hot right out of the factory. It was such an issue that Gm was going to recalibrate the gauge(to lower) to stop warranty inquiries according to him. It's a poor design that we have to work around and keep everything on the list covered because it is gonna run hot if you don't.
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post #7 of 116 (permalink) Old 02-24-2008, 09:02 AM
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Removing the thermostat could also cause overheating as the coolant will go through the motor so fast it won`t be able to extract heat from the block.
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post #8 of 116 (permalink) Old 02-26-2008, 05:29 PM
 
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Quote:
Originally Posted by seamus2154 View Post
When I lived back in NY there was a guy named Nunzi in Bklyn, who was a guru and big racer of pontiacs. Had a very popular garage. He was in the game from day one and I had the same dilema in the eary 80's. He explained everything on your list and added that these cars ran hot right out of the factory. It was such an issue that Gm was going to recalibrate the gauge(to lower) to stop warranty inquiries according to him. It's a poor design that we have to work around and keep everything on the list covered because it is gonna run hot if you don't.
Wow ..I remember Nunzi !! I am an old GTO fan from the mid 70,s.



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post #9 of 116 (permalink) Old 07-28-2008, 09:42 AM
 
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Low Oil

If you are burning or leaking oil at a slow enough rate that there are no obvious signs (black smoke out the exhaust or spots in under the car after parked) and you do not check the oil frequently - oil level gets low, does not cool the engine effectively, the radiator and water pump have to carry more load than designed for - and before ya know it your '67 LeMans blows a hose on the highway half way from Mount Pleasant Michigan to East Lansing. Just hope you are lucky enough to have a guy in a 66 and a half Camaro see everything and stop to help you, drive you to the next exit and find an autoparts store with the necessary parts in stock and take you back to your stricken vehicle.

Or - having someone rebuild the Tri-Power Carbs in your '64 GTO and not have the thick rubber gasket that goes between the manifold and the top of the timing chain cover and use silicone instead - only to have the silicone fail somewhere near White Plains New York while on your way from Cleveland, Ohio to Amherst, Mass. Just hope you are lucky enough to have a friend whose dad owns a rental property about 3 miles away who happens to work at a service station and helps you take the car apart enough to fix the problem and that there is an auto-parts store around the corner that has the correct gasket kit in stock. Just be careful you don't put a pin hole in the radiator in the process.
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post #10 of 116 (permalink) Old 01-19-2009, 03:36 PM
 
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The compression ratio is too high for the gas that is available today.
I read the statement on RRE's website at

Serious Pontiac Horespower - Rock and Roll Engineering

It made sense to me; my 67 GTO has always run hot because the compression ratio is still at 10.5:1, which is too high. I’m starting to assemble parts for the next engine, it will be 9.5:1 or less.

Chip

Last edited by chip_bridges; 01-19-2009 at 03:38 PM.
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