tomz240

02 C5 temp gauge maxes out above 60 mph and a/c shuts off, but no physical signs of engine over heating. Idle for 5 minutes gauge goes back to 190-200. What’s up? Sensor maybe?

gimp

Coolant temp shoots up driving at highway speeds but not idling? The opposite of a common issue, so your radiator probably isn't dirty. Is your coolant level adequate? Have you burped the coolant? Is your water pump leaking or showing other signs of failure?

tomz240

Coolant level good. Haven’t burped. Cool at idle according to gauge. No visible leaks and nothing has boiled over as of yet.

Bill Curlee

How do you know that the engine is not over heating?? Have you used any measuring devices to check the engine block temps?? Purchase a cheep inferred laser temp tool and measure the block and water pump thermostat housing when it overheats (GAGE shoots up)

The coolant sensor and connector are on the head just below #1 spark plug. Remove the connector and inspect the connector and wiring harness. If it were me, I would change out that sensor.

YES,, If the sensor reports overheat to the PCM, the AC will shut off as its programmed to do to remove that extra load from the engine and cooling system.

TRUST ME, if the engine was actually overheating, it would not just magically POP back into specs when you went below 60MPH. It takes a LONG tome to cool the overheated block back down once it reaches critical temps.

IF, you are low on coolant and there is steam in the heads, it could act that way.

BURP the cooling system using the steam crossover pipe fitting bolt at the front of the heads and see if the block is full of coolant. If you crack that fastener loose,(DO NOT FULLY REMOVE THE BOLT IF THE ENGINE IS HOT!!) you should see coolant flow out. If there is air in the system it will escape and then the coolant will flow out!


BC

tomz240

I will try all of this out.
Thank you Bill.

gimp

Hey Bill, great advice as always. Do you recommend cracking the left fastener (looking from the front backwards) on the coolant cross-over, or the right, or both?

3sACROWD

Try turning your heater and fan on high when driving above 60MPH. Does that help your issue? What did you recently do to your car?

Have you physically looked under the car? Maybe something is stuck under the car and flips up at speed to block airflow or your AC condenser is blocked / plugged. .

tomz240

Just installed a front spoiler. Nothing blocking.

Bill Curlee

I normally do one (doesn't matter what side) but, if I am not fully satisfied, I will crack open both one at a time. Pick what ever bolt is easiest to get to.

3sACROWD

Doesn't look like your spoiler has any openings; correct? Did you remove the center air dam during install? If yes to one or both above, you aren't pushing any air up to the radiator. The heater trick I mentioned above would likely confirm that as would removing the spoiler (which I think would be a pain).

Edit: Openings look small in the spoiler. Didn't have a good view on my phone. Retracted comment about Z06 openings as they are for cold air to intake.

tomz240

Ok. Looked under the car and there is no air dam. I’ve only had the car since March. So is this most likely what’s causing my problem?

bravo29

I can verify this on mine. My air dam broke off and had a similar issue. I put on a new air dam and issue went away. With out the air dam my temps were all over and high. Air dam on and I am back to normal temps.

tomz240

Missing air dam was the problem. Installed new one. Running nice and cool now.

redzg

Don’t you just hate it when the engineers had it right?