Went to an AutoX event this weekend; I didn't run the car all that hard. Ambient temp was about 80 degrees, I only ran about 8 times, and I would only do 2 runs and shut it down; the oil temp didn't get above 214 degrees. Driving home, my coolant temp starting going crazy; it went from 205 to 265 degrees in the span of 40 seconds or so and this was doing 65mph on the highway in 6th gear. I shut the car off and the coolant temp got back down to 205 in about 5 minutes, then I tried to start it and drive and it went back up to 265 degrees in about 30 seconds. The fans were blowing as hard as they could but the coolant temp gauge still was pegged in the red. I left the car at a gas station and had some dinner, then came back 2 hours later and started it up to see how far I could get. A few miles down the road, I got stuck in traffic thinking I was going to overheat for sure; but the coolant didn't get above 205 degrees. The oil temp never went about 215 degrees during any of this.

I had this happen once before about 8 months ago after a day of drag racing, but I was able to tow the car home and I flushed and filled the colling system and replaced the factory thermostat with a Hypertech 160 stat. The problem didn't come back through any subsequent days of racing or driving until this weekend. The only constant things both days were the fact that I was racing and the car was left outside the night before and had condensation all over it during a 50 degree morning. Mods, tune, and type of racing were totally different.

Anyone have any idea what may have happened or had this happen to them before? I'd like to get this fixed before an October track day at Road America . Thanks!

 

it might just be the sensor going bad. theres not that much else it could be either the sensor or the water pump. But my moneys on the sensor.

 

Cool, it's worth the $20 to make sure that's not the problem!

 

Clean out your raidators. Before each track weekend take a high pressuer air hose, and a thn brush, dry vent brush, and get all the grass, dirt, and what ever else is in there out.

2nd get two bottles of water wetter. That will drop temps too.

Check your sensors, and your water pump.

Rember as your skill level goes up so does your driving and cars temps

 

Check the wiring that goes to the sensor as well, if you have a softset pin or a damaged wire, it could make an intermittant connection making the readings go all over the place.

 

I had sort of a similar experience recently, and all I've done to fix it was to replace the pressure cap on the overflow tank (rad cap).

My car started overheating sitting in traffic one day. Once I got it back up to speed everything was OK. Got it home and popped the hood, noticed that while idling the coolant level was low and air bubbles were being sucked down into the coolant lines from the tank.

Replaced the rad cap, topped up the tank with water, drove for a bit, topped off tank again. I drove the car for about three weeks before the coolant level finally stabilized. I thought at the time there was a leak somewhere, but I think it just took that long to finally work all of the air out of the motor.

My THEORY on what happened was that the rad cap was bad and was allowing steam to exit whenever the engine warmed up and pressure built in the cooling system. Over time that steam was enough to get the coolant low enough to allow air into the system. Once enough air got in, the water pump started to cavitate or run dry, coolant flow stopped, and my motor overheated. Once the revs came back up the pump got the coolant flowing again and all was well.

Check your rad cap; remove it and wipe off the bottom well. Put your mouth around the base (the part that sticks into the tank, not the outer threaded body unless your mouth is HUGE) and try sucking and blowing through the cap. You should be able to suck air in through the cap but not blow air back out through the cap.

I tried this on mine and it failed the test, '02Z with ~73k miles at the time of failure. Replacing the cap has been the fix so far, coolant level has been steady for about a month now.

 

Good suggestions, everyone. It seems as though it's something very small that just doesn't like it when I drive the car hard for an extended period of time. I'll try all these suggestions and see if the next AutoX causes any problems.

Thanks!

 

Are you certain that both fans were running? I had an instance where the low speed fan motor was dead and the car would try to run hot on long gradual climbs and hills.

Once I replaced the low speed fan motor, everything was cool.

 

I did check to make sure both fans were running and they were. Thanks for the suggestion!

 

[QUOTE=Blue Angel;1561210390]I had sort of a similar experience recently, and all I've done to fix it was to replace the pressure cap on the overflow tank (rad cap).

My car started overheating sitting in traffic one day. Once I got it back up to speed everything was OK. Got it home and popped the hood, noticed that while idling the coolant level was low and air bubbles were being sucked down into the coolant lines from the tank.

Replaced the rad cap, topped up the tank with water, drove for a bit, topped off tank again. I drove the car for about three weeks before the coolant level finally stabilized. I thought at the time there was a leak somewhere, but I think it just took that long to finally work all of the air out of the motor.

My THEORY on what happened was that the rad cap was bad and was allowing steam to exit whenever the engine warmed up and pressure built in the cooling system. Over time that steam was enough to get the coolant low enough to allow air into the system. Once enough air got in, the water pump started to cavitate or run dry, coolant flow stopped, and my motor overheated. Once the revs came back up the pump got the coolant flowing again and all was well.

QUOTE]

Had same problem when first got my vette. Got a new GM cap and solved the problem.