# GTO overheating on temp gauge



## Rezombie (Mar 23, 2009)

I have had my GTO for about 4 years and just recently rebuilt my engine(400 bore over .20), trans(350TH), suspension(Moog), and brakes(BAER brake systems) also everything is new in the motor in and out. Everything that involved motor wise to run properly. Up until recently I had gotten back from going for a job and came back 6 months and haven't put on more than 400 miles on the motor before leaving I had the problem prior to leaving, but thought cause it was fairly new that it was normal. I'm having problems with the temp gauge where it moves up and down rapidly all of a sudden from 190 to 220 to 240 and then jumps down to 230 and then 190 after using the car for more then 20 minutes. This is all happening in about 2 to 7 seconds then idles at 220 to 230 and then when I stop or arrive at my destination I shut it off. Then when I turn it on(Not even 5 mins later), its a little harder to start and idles at 190 degrees just fine, once again then starts up again after 20 mins. When my motor gets warm and I use it for a while it also makes a clicking noise only when the motor is warm and the temp is doing what it does. I have no idea why it does what it is doing. I have a new radiator(Desert cooler 4-core), thermostat (180 stock), and water pump from OPGI(Original Parts Group In-corp, I purchased a "Milodon" High Performance aluminum water pump.) I'm worried that my motor was rebuilt improperly or that something was defective. If anyone can help I would greatly appreciate it. Thanks.


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## Instg8ter (Sep 28, 2010)

when you put the pump on did you clearance the impeller to the divider plate, this is the most common reason for overheating in our engines. i would put a new 180 thermostat in too, sound like yours may be sticking. your good around 200 degrees.


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## jetstang (Nov 5, 2008)

Sounds like the thermostat is sticking, I'd replace it. I put my new motor in with a failsafe stat, and it failed closed on the first drive and my radiator blew, literally, popped the core, I will never use a failsafe stat again. Thermostat modulates pressure, some new ones are bad. Now, after not driving it forever started drivin it and gauges were jumping like yours, noticed all of them were jumping, think its a ground issue.. After driving, all my gauges work fine, can't explain that, guess it's getting grounded, lol, with use..


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## geeteeohguy (Feb 2, 2008)

I'd check the gauge and the grounds to the gauge. Verify actual temps with a pyrometer. Temp fluctuations of 40 degrees in 2 to 7 seconds as you describe is not possible in your cooling system...thermally not doable. If you _are_ actually running hot, (verified with a pyromenter) then yes, what Inst and Jet said is good advice.


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## Eric Animal (Oct 28, 2007)

:agree verify temps with a thermal image thermometer (nice tool to have and not too expensive).....the gauge/sender/ wiring COULD be faulty......


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## BearGFR (Aug 25, 2008)

From your description, my first thought also was sticking thermostat. I'd go ahead and replace it --- they're cheap and easy (sort of like me ) --- and see if that takes care of it. I also agree that having that wide of a temp change over that short of an interval is pretty hard to pull off... but I can tell you that on the Beast, during the time when it had a propensity for tossing belts, when it did that "under power"  it could go from 160-180 to almost pegged by the time I could get the car stopped.

Bear


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## Eric Animal (Oct 28, 2007)

And remember....always double tap! :cheers


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## Instg8ter (Sep 28, 2010)

Daughter likes shooting the Zombie targets when we go to the range...:shutme


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## Rezombie (Mar 23, 2009)

Thanks for the help guys change the gauges, had old ones for the volts and oil pressure. All three are new and shinning a bright red which match the car :rofl: but I thinking it wasn't my temp gauge cause now. I didn't notice how much that noise was affecting it and where it was coming from, but... its coming from the manifold and the thermostat area. A type of clicking noise when you have metal clicking metal but faint not too loud and when that noise appears the temp is doing what it normally does (running hot). When I had my friend remove the water pump it was all corroded and had corrosion along where the gasket was. He also told me that if something was in the motor that went to the radiator that it kinda clogged one of the cores and caused it to run slower. I hope my motor is not ruined....


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## Instg8ter (Sep 28, 2010)

while he has it off make sure you clearance the plate (above video) and flush out the system and radiator real good. I would replace the temp sending unit (plug) also while its apart and make sure it is compatible with your new gauges. as long as you were under 210 and did not push it any higher with load you should be OK. Like the guys said get a thermal meter on it and find out the exact temp, only verified gauges can be trusted.


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