Was out at PMI today. Granted it was over 100, but in the last two sessions this afternoon during like the 4-5th lap the coolant temp suddenly jumped from like 228 into the red. Both times I backed off, went into the hot pits, and by the end of the hot pit was right back to 228. Kinda like turning a switch on and off (fan, thermostat?). I looked for hose kinks, but didn't see any. I'm thinking the 1st place to start is the coolant. Before tracking the car the first time I changed all the fluids - except the coolant. It's probably the original. So that's the first thing I'll do. But could I also have a fan or thermostat issue? Whole system is stock except for some Water Wetter added to the coolant.
Check the simple stuff first since you're in the "field". I'm assuming your coolant level is OK. Are your fans coming on? Do the coolant temps on the DIC mirror the gauge temps?
If the above check out then I would look next for leaves & other debris that may be stuck between your radiator and A/C condenser. You might need to remove your air bridge and air cleaner to get access from the top.
Thanks, I'll give that a look. Yes, level is full, and color is good. Checked it yesterday before I left when the car was cold. And the oil temp remained stable even when the coolant spiked.
Interesting development. A guy who drives an CTS-V (Andrew) with the same drivetrain experienced the exact same problem today. We both ended up running with the heat and A/C on, and saw our coolant temps come down to the 200 range. Got bumped to 3, and a rented traqmate tells me I broke into the 1:49's.
From the GM manual.
"The low speed cooling fan is commanded on when the coolant temperature reaches 108°C (226°F). It is turned off if the coolant temperature lowers to 104°C (219°F). The high speed cooling fan is commanded on when the coolant temperature reaches 113°C (235°F). It is turned off if the coolant temperature lowers to 108°C (226°F). When the A/C is on and the coolant temperature reaches 85°C (185°F), the low speed cooling fan will be turned on at vehicle speeds less than 56 kPh (35 mph)."
So with the A/C off the fans only cool to around 220!
This is why many owners reprogram the fan on/ off temps. I used a Predator programmer to change mine and installed a 170 thermostat at the same time, problem solved. Also make sure that the front of your radiator is clean, corvettes tend to vacuum everything on the road up into it.
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From the GM manual.
"The low speed cooling fan is commanded on when the coolant temperature reaches 108°C (226°F). It is turned off if the coolant temperature lowers to 104°C (219°F). The high speed cooling fan is commanded on when the coolant temperature reaches 113°C (235°F). It is turned off if the coolant temperature lowers to 108°C (226°F). When the A/C is on and the coolant temperature reaches 85°C (185°F), the low speed cooling fan will be turned on at vehicle speeds less than 56 kPh (35 mph)."
So with the A/C off the fans only cool to around 220!
This is why many owners reprogram the fan on/ off temps. I used a Predator programmer to change mine and installed a 170 thermostat at the same time, problem solved. Also make sure that the front of your radiator is clean, corvettes tend to vacuum everything on the road up into it.
At speed the fans play little into cooling... From personal experience I can say running hard - that the stock radiator does not provide adequate cooling for sustained high RPM and track fun in 100F+ degree weather.
You lay off the gas and you will see immediate cooling, but once your on it again up goes the temperature. Very typical in the heat.
A more important question is, what was your oil temp? Oil temp is going to be higher than water temp. On the track you should have the DIC on this. With outside temps of 100F+; within 10 minutes I could easily get my oil temp to 290F+ which would make coolant temp all that much higher while running the factory radiator. Easily reach oil temps of 300F and I would have to back off, let things cool down, get on the gas and do it all over again!
Once oil temp hit 300F+ you start running the risk of serious problems. Bearing failure...
Solution... real radiator with an engine oil cooler if you want to play on the track in hot weather! If you are a track junky this is something you should add to you wish list in any case.
2009 SCCA Colorado & Continental Divide Region SSM Champion
2008 SCCA Colorado & Continental Divide Region ASP Champion
2001 SCCA Oregon Region Street Modified Champion
Solution... real radiator with an engine oil cooler if you want to play on the track in hot weather! If you are a track junky this is something you should add to you wish list in any case.
Ron, good advice. I run at the track with the oil temp displayed in the DIC, and check all gauges on straights if I’m not passing. I saw as high as 285, but not above. When the coolant temp went back down, and the warning cleared from the DIC I checked the oil temp cruising down the hot pits, and it was still 285. Don’t know what it was in between, but I sure babied the car into the hot pits. I made the decision last night to say goodbye to stock class autox, and begin the process of making the car more track worthy as that’s my priority going forward. I’m hopelessly addicted. But first comes the autopower roll/harness bar I’m awaiting arrival of, and racing seats and harnesses. Safety first!
And who knows, I might even end up with a wing on my Corvette.
Despite this glitch the car was simply amazing on Friday. 100+ degree’s, and around 4 hours and 100+ laps. She took it all in stride, and after a brake bleeding came back for more the next day! She’ll be getting a lot of well deserved TLC before she see’s the track again in August.
Ya, a DeWitts is in your future if you want to track in CO a lot. The altitude, the low humidity, and the heat make it difficult. Fan and thermostat don't factor in on the track.
Did you loose any coolant before it started to spike? Debris building up will cause issues as well, PMP is pretty dirty. Did you drop any wheels? Or someone in front of you drop a wheel? Its amazing how much junk can build up fast...
I was at 220 at the most on Sunday, but that was in the morning. I did something to the engine and had to retire early.
Ron, good advice. I run at the track with the oil temp displayed in the DIC, and check all gauges on straights if I’m not passing. I saw as high as 285, but not above. When the coolant temp went back down, and the warning cleared from the DIC I checked the oil temp cruising down the hot pits, and it was still 285. Don’t know what it was in between, but I sure babied the car into the hot pits. I made the decision last night to say goodbye to stock class autox, and begin the process of making the car more track worthy as that’s my priority going forward. I’m hopelessly addicted. But first comes the autopower roll/harness bar I’m awaiting arrival of, and racing seats and harnesses. Safety first!
And who knows, I might even end up with a wing on my Corvette.
Despite this glitch the car was simply amazing on Friday. 100+ degree’s, and around 4 hours and 100+ laps. She took it all in stride, and after a brake bleeding came back for more the next day! She’ll be getting a lot of well deserved TLC before she see’s the track again in August.
I am not sure what its set at or if there is an engine oil temp alarm. Mine peaked 305F once and never had an alarm. I just watch it like a hawk, but with an EOC it solved that problem.
There is still lots you can do and stay in stock. A roll bar is allowed in any AX class. Obviously if you go with racing seats then I think you go up to ASP. Lots can be done in ASP.
If you don't already have a full brake air duct and don't notice not having one then your not going fast enough! That helps too!
I did run the wing at the CSP track, but took the top plane off. Figured one plane at 15 degrees is more than enough for high speed stuff! The top one at 40 degree would just cause too much drag and a rediculous amount of down force!
I'd be out there with ya, but can't afford to be serious in more then on hobby at the moment!
Sounds like a bunch from the SCCA and the Corvette club are going out to HPR on the 17th.
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Coolant temp problem
