C5 Intermittent Overheat
Thread Starter
Heel & Toe
Joined: May 2022
Posts: 18
Likes: 0
From: Fort Wayne IN
C5 Intermittent Overheat
Hello,
I have a C5 with mild upgrades that has recently developed an intermittent overheating problem.
Fans are functioning and radiator is clear of debris. I replaced the thermostat and housing which seemed to solve the problem in all but a few specific scenarios most prevalent of which being, idle with the A/C on.
Idleing with the A/C will rocket the temp from 220 to 235 in less than two minutes before I intervene to cool the car down. (Not sure how high it’ll go before it boils over again and don’t really want to find out)
Lots of posts about overheating but not many with these specific issues.
Any advice is appreciated!!
I have a C5 with mild upgrades that has recently developed an intermittent overheating problem.
Fans are functioning and radiator is clear of debris. I replaced the thermostat and housing which seemed to solve the problem in all but a few specific scenarios most prevalent of which being, idle with the A/C on.
Idleing with the A/C will rocket the temp from 220 to 235 in less than two minutes before I intervene to cool the car down. (Not sure how high it’ll go before it boils over again and don’t really want to find out)
Lots of posts about overheating but not many with these specific issues.
Any advice is appreciated!!
Pro
Joined: Dec 2014
Posts: 683
Likes: 275
From: Cincinnati Ohio
Sitting at idle, with the a/c on, and in summer weather, your coolant temperature will cycle with the cooling fans switching between low and high speed. 235 degrees with a 50/50 coolant mix and a 15 or 18psi “radiator” cap is not over heating. Under the idle condition you described, what happens if you let it run? Does it continue to cycle up to 235 and then drop or does it keep going up and up to 240, 250, 260?
Thread Starter
Heel & Toe
Joined: May 2022
Posts: 18
Likes: 0
From: Fort Wayne IN
Sitting at idle, with the a/c on, and in summer weather, your coolant temperature will cycle with the cooling fans switching between low and high speed. 235 degrees with a 50/50 coolant mix and a 15 or 18psi “radiator” cap is not over heating. Under the idle condition you described, what happens if you let it run? Does it continue to cycle up to 235 and then drop or does it keep going up and up to 240, 250, 260?
Le Mans Master
Joined: Feb 2021
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From: Florida
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Do the fans ever go to higher speeds around 230° ?
Should have a second stage. The other thing that comes to mind is an air pocket in your cooling system.
Should have a second stage. The other thing that comes to mind is an air pocket in your cooling system.
Thread Starter
Heel & Toe
Joined: May 2022
Posts: 18
Likes: 0
From: Fort Wayne IN
Would there be anyway to verify the fans hit stage two? Im fairly confident there isn't an air pocket but I suppose I don't know for sure.
Melting Slicks
Joined: Sep 2008
Posts: 3,138
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From: Espanola New Mexico
You should be able to hear the fans go into high speed mode as they will turn twice as fast. You mention in your first post that the fans are operating correctly, so both fans come on at low speed at the lower temp set point, and then go to high speed at the upper temp setpoint?
Thread Starter
Heel & Toe
Joined: May 2022
Posts: 18
Likes: 0
From: Fort Wayne IN
You should be able to hear the fans go into high speed mode as they will turn twice as fast. You mention in your first post that the fans are operating correctly, so both fans come on at low speed at the lower temp set point, and then go to high speed at the upper temp setpoint?
at what temp would they go into high speed?
Race Director
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Thread Starter
Heel & Toe
Joined: May 2022
Posts: 18
Likes: 0
From: Fort Wayne IN
Gotcha, any idea what the culprit there would be? I’m not to privy to electronics so I’m not sure what would cause one speed to work but not the other
Thread Starter
Heel & Toe
Joined: May 2022
Posts: 18
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From: Fort Wayne IN
So I replaced all cooling fan relays to no avail. Both fans continue to work as expected (w/high speed now) but the car rocketed to 240 idle with A/C on before I intervened.
Moving along 30mph+ temps are normal but as soon as I stop it went straight up
Moving along 30mph+ temps are normal but as soon as I stop it went straight up
Le Mans Master
Joined: Feb 2021
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From: Florida
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Water pump? Seems like a flow issue. Or thermostat which are known to have defects. Just think it’s not opening fully starving the radiator at lower flow. Have you tried another stat?
Another option, take it to shop to drain the coolant, and then pull a vacuum on the system and fill with a solid stream of fluid. This method virtually assures no air pockets.
Another option, take it to shop to drain the coolant, and then pull a vacuum on the system and fill with a solid stream of fluid. This method virtually assures no air pockets.
Thread Starter
Heel & Toe
Joined: May 2022
Posts: 18
Likes: 0
From: Fort Wayne IN
Thanks for all tips everyone, I’ll answer a few questions and give some history here:
I’ve replaced the thermostat, all fan relays, and coolant here in the past week. Fans are now working properly (both fans, both speeds) and the new thermostat helped with temps from before it was replaced, coolant levels are a-ok
I’m not entirely convinced it’s an A/C compressor problem as I have ice cold and steady air conditioning but again I’m not well versed on these topics.
praying it isn’t a radiator or water pump as I really don’t feel like tying the car up for any period of time.
I’ve replaced the thermostat, all fan relays, and coolant here in the past week. Fans are now working properly (both fans, both speeds) and the new thermostat helped with temps from before it was replaced, coolant levels are a-ok
I’m not entirely convinced it’s an A/C compressor problem as I have ice cold and steady air conditioning but again I’m not well versed on these topics.
praying it isn’t a radiator or water pump as I really don’t feel like tying the car up for any period of time.
Drifting
Joined: Mar 2018
Posts: 1,365
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From: New Jersey
If you come to a stop and then hold the engine at around 2k rpm does it still overheat? Conversely if you coast at 40 mph with the engine idling does it over heat?