C5 Intermittent Overheat
Le Mans Master
Joined: Feb 2021
Posts: 6,508
Likes: 4,355
From: Florida
2025 Corvette of the Year Finalist - Unmodified
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Theres a bunch of videos on YouTube above dirty C5 radiators. It doesn’t have to be big chunks to degrade the low speed cooling.
Pro
Joined: Dec 2014
Posts: 683
Likes: 275
From: Cincinnati Ohio
What temperature are you running down the road at 30mph and above on a Ft Wayne 90 degree day? A/C on or off you should be under 200 F if all is normal.
Did you already write in earlier posts that all three pieces of your air dam are in place? The air dams serve two purposes.
1. To direct air to the condenser when moving. C5’s are bottom breathers.
2. To prevent recirculation of hot air exiting the radiator from flowing back to the condenser.
Did you also confirm that your lower radiator hose is under pressure, very firm when you squeeze it (with a gloved hand because it is also very hot).
Did you already write in earlier posts that all three pieces of your air dam are in place? The air dams serve two purposes.
1. To direct air to the condenser when moving. C5’s are bottom breathers.
2. To prevent recirculation of hot air exiting the radiator from flowing back to the condenser.
Did you also confirm that your lower radiator hose is under pressure, very firm when you squeeze it (with a gloved hand because it is also very hot).
Drifting
Joined: Jul 2015
Posts: 1,844
Likes: 375
From: San Jose, CA
Update:
the car is now overheating at idle *Without AC*
this has to be radiator I imagine. I’ve replaced thermostat, relays, the fans are working properly etc.
the car is now overheating at idle *Without AC*
this has to be radiator I imagine. I’ve replaced thermostat, relays, the fans are working properly etc.
Race Director
Joined: Oct 2004
Posts: 12,864
Likes: 4,667
Boo. 160 degree thermostat controls when coolant starts being fully routed through the radiator. It does not affect how hot your coolant gets, after it goes past 160F. A lower-temp thermostat will not affect an overheating issue when coolant reaches 100F higher than the thermostat's rated opening temperature. Please don't suggest a cooler thermostat to solve an overheating issue unless a person's thermostat is (1) not working at all, or (2) hilariously high and way the hell out of spec for a corvette, like a 240F thermostat, which would be a real sight to see.
Race Director
Joined: Oct 2004
Posts: 12,864
Likes: 4,667
After reading, and re-reading the OPs posts, it sounds like either the radiator is marginal, or it's not getting enough air. Be absolutely certain your radiator is clean and no debris is plugging it. You may need to pull your fans (not a big job) to access the rear of the radiator, and then use some sort of air to blow forward to clear years worth of small bugs outta there!! I made up a small pipe that screwed into my air nozzle, then put a 90° end on it. Use about a 2ft long piece of 1/16-27 NPT pipe, and a 90° street el. It will make a difference. Vette4fl made some good observations, and suggestions. He lives in Florida. If he can keep his car running cool there, it'll be good anywhere!!!
