326 overheating - Pontiac GTO Forum
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post #1 of 14 (permalink) Old 02-16-2016, 02:55 PM Thread Starter
CPL
 
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326 overheating

New waterpump,radiator, hoses,and had to bad thermostat s,running without one now still over heated.326 was rebuilt about 200 miles ago,radiator was also..any thoughts?
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post #2 of 14 (permalink) Old 02-16-2016, 04:04 PM
 
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The Pontiac water pump to intake opening and the metal gaskets have to be set up correct,...that is a common problem on pontia so.....


but a bad fan clutch can cause it as well, blocked passages even a blocked exhaust or stuck heat riser in exhaust manifold can make it run hot.....



I would check the fan clutch and put in a thermostat......make sure you have no hidden anti freeze leaks
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post #3 of 14 (permalink) Old 02-16-2016, 04:16 PM
 
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Are you just running hot, overheating to the point of the pressure cap blowing, or does the cap blow after you shut off?
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post #4 of 14 (permalink) Old 02-16-2016, 05:41 PM Thread Starter
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It seems to run hot then boils over into the Reservoir two thermostats have been bad DOA I took the thermostat out this morning dropped it into some hot water it opened at 211 Degree. it was supposed to open at 195 I did exchange the bad thermostats and got a new one set to open at 180
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post #5 of 14 (permalink) Old 02-16-2016, 05:44 PM Thread Starter
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I have just a solid original type fan hooked onto the water pump so it turns constantly and also I have headers not a manifold which of course the headers get pretty warm
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post #6 of 14 (permalink) Old 02-16-2016, 05:55 PM
 
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I'd venture to say 95% of overheating issues on these cars are caused by improper timing. I'd start checking there with a timing light and vacuum gauge. Best to check total timing and not just static. If all is well, move onto some of the suggestions here including the water pump divider clearance and the fan clutch. Also, when installing the t-stat try drilling a couple 1/16" holes 180 degrees apart on the outer rim. This allows some air to move through the system and prevents air lock heating issues.

There's quite a few threads on the board covering this topic so you might find some good solutions by doing a forum search. Good luck and post back your findings. Once you narrow down probable causes we should be able to help pinpoint your issue.

Andy
'67 GTO/Signet Gold over Parchment/Pontiac Built
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post #7 of 14 (permalink) Old 02-16-2016, 06:01 PM
 
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Is the new thermo installed? Did you test it? Sorry to be Irish and answer a question with a question. With a rebuilt motor it could be a lot of things, starting as Lemans Guy said with a bad install of the WP. My '67 GTO ran hot due to timing and mixture.
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post #8 of 14 (permalink) Old 02-16-2016, 06:08 PM Thread Starter
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No I have not installed the new thermostat yet I did however run it without the thermostat and it did not overheat
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post #9 of 14 (permalink) Old 02-16-2016, 06:33 PM
 
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Garage
Make sure you have the correct radiator cap on. I changed mine from 15psi to 16psi when I was having issues, and it solved the problem.

Also, check to see if your bottom radiator hose is pinching - may have to add a spring.

Couple easy things to check first...

Mama always told me not to look into the eyes of the sun; but mama, that's where the fun is...
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post #10 of 14 (permalink) Old 02-17-2016, 06:48 PM
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Keep in mind that with only 200 miles on your engine, it will run a bit hotter. When it's broken in at 500-1000 miles, it will cool down a bit.....like 10-20 degrees.
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  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, Lemans & GTO General Discussion

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