VetteDrmr

When I run an autocross on a typical slow (mainly 1st, some 2nd) course I'm running into high coolant temperatures.

Before this season I pulled the radiator out of the car, brushed, washed with soap&water, and hosed out a large amount of muck out of the radiator fins. It helped a fair amount, but at last Saturday's autocross I ran into heating problems once again.

When I compared notes with a fellow C5 competitor he was running probably 10-20 degrees cooler than me. He was also faster than me by about 1 second, so I expect he was running his engine at least as hard as I was.

The only real difference engine-wise between his car and mine is the mileage. I've got 210K miles, his is under 100K.

And, just to complete the picture, I have no problems at all during normal street driving.

Question: does a radiator and/or water pump just lose efficiency with mileage? Coolant is normal, and as I mentioned it's been cleaned recently.

Thanks for any help, and have a good one,
Mike

varkwso

Yes, due to the inevitable corrosion, a radiator will lose efficiency with age. Pumps also lose effieciency with age and use.

Also with age an older engine will "leak" more heat into the cooling system.

VetteDrmr

Thanks for the response. I hope we've got past the hottest events for the year (I don't seem to have this problem as much on higher speed courses or tracks), and I may be retiring my baby from active competition after this season. However, if I decide to keep autocrossing her next year I'm going to start looking for a replacement radiator and water pump.

Thanks again, and have a good one,
Mike

davidfarmer

are you actually overheating, or just running hotter than you think it should? How hot is it getting????

VetteDrmr

It seems to be getting hotter than it should be, comparing two C5s running reasonably close times with similar engine mods (LT headers and a tune).

I had to pull out of line after my3rd run in the afternoon (it was over 100 in the shade, probably 140+ on the black parking lot pavement) to cool down with the fans. Coolant was around 235-240, I got it cooled down to 220 before I took my 4th afternoon run. This was on a 60 second course, probably 70% 1st gear.

rustyguns

240's not bad, what were the oil temps? we run hot in AZ

johninar

I think what's interesting is the temps ABOVE his norm. In some ways it's similar to mine. I was running warmer than normal, but not overheating. Where I would be 210-220 I started running 220-235+. I used a NAPA head leak detector to confirm the leaking head gasket. After pulling the heads we could see 3 cylinders that were burning water, clean as a whistle. I wonder if you are suffering from a leaky head? I never saw anything in the coolant, nor did my oil analysis show any coolant. Just a thought, I'm no mechanic so take it for what it's worth.

Do you hit the rev limiter a lot?


Good luck with it.

VetteDrmr

Here's a video from Saturday, so you can at least hear how the engine was winding up:

http://www.youtube.com/watch?v=71uikfN8oj8

Rusty, I run an external air-cooled oil cooler, so oil temps were only 5-10 degrees warmer than the coolant.

John, that's an interesting observation. I get my oil analyzed by Blackstone and there's no evidence of coolant in the oil, just like yours. What is a head leak detector?

I don't have a problem tapping the rev limiter, but I don't hammer on it, and it's hit only occasionally.

The other interesting point is that when I'm on the track (out at MSR or ECR, for example) I don't have this problem, although the engine is at WOT for longer periods of time. During those runs coolant temps are in the 220s and oil temps up around 250.

Thanks for the comments, and have a good one,
Mike

johninar

http://www.napaonline.com/Search/Det...006_0282386404

longdaddy

if you are overheating at auto-X bit not at the high speed tracks, this would point to problems with the fans.

If I had seen 240 water temps at an auto-X event, I would be pretty convinced that something is wrong with the car.