Hey guys, hopefully you can help me out with My C5. So I take the car for a drive on the streets and turn on the AC and the temp will climb to 226 F when I am on the freeway the temp will climb to 235 and even as high as 243 and keep climbing, i usually have to kill the AC and take it easy the temp will fall to 226 and stay (no AC on) my questions is do you guys have this problem too? Is it because it's a big engine and the car runs hot? Or do you think there is cooling problem, I have checked for air pockets, changed the radiator, changed the cap twice, refilled the fluid, checked the fans, changed the thermometer and taken it to the dealer only to have them say the system shows no errors""...and if I decide to drive on the freeway up a hill with he AC on the temp will climb and climb well up to 243 and higher if I let it...keeping in mind the max temp on the car red zone is 260...any help would be greatly appreciated, not sure what else to check or change at this point

 

Your symptoms are opposite of what usually happens, most of the time the temps will go down with the A/C on. Is your car stock? Mods, if any what are they...

For your cooling system to work properly you must have a working thermostat, a working purge tank cap, a working water pump,air in the system, fresh properly ratio coolants, clean free flowing A/C condenser, and radiator, properly working air dam, properly working fans, I'm probably missing a few other things but, if it's something other than these I don't think you'd be seeing 245 on the freeway..my guess is water pump.

 

The car is stock, and I had changed the water pump as well, I am not familiar with the air damn, the fans are all good, and I have tried changing the coolant too but no success , any other suggestions? And thanks for your help!

 

They have been installed backwards, make sure it's in the correct position.

 

Possibly the temp sensor is wrong and your getting higher readings than the actual temp? Pressure test system?

 

How can I check to see if it is reading accurately or not? What is a pressure test?

 

Have you cleaned the fins on the rad and condenser?

 

-Heres the deal! If you went back in time and picked up the SAME car form the dealer NEW,, it is designed to operate properly in Alaska to Death Valley.

So,, yours is operating HOT. At least that what the gage says.

Your cooling system consist of a water cooled block that flows a mixture of water & "organic acid technology," or OAT antifreeze. It's orange!

The mixture MUST be correct for the operating conditions that you are operating in.

Some of the things that make your car cool properly are:

- Full cooling system. No air pockets in the block.
- Good Thermostat.
- 50/50 to 60/40 antifreeze to water mixture.
- Properly operating Fan/s and fan speeds
- Clean radiator able to flow proper air through the fins. The air has to flow throught the AC Condensor & the radiator.
- Proper radiator ducting and shrouds and air dams. The air comes from under the car and flows through the radiator, the fans SUCK the air through the radiator at low speeds.
- Water pump to circulate the coolant from the block and through the radiator.
- You have two fans and three fan speeds, and the PCM operates the fans through relays.


Questions & recommendations:

- Do your fans operate properly?
-Is the radiator, condensor and the 1" space between the two able to flow max air? ie. NOT CLOGGED!
- All the fan and radiator shrouds and air dam functional?
- Coolant to water ratio? Measure it with the proper hydrometer and make sure that it has the proper boil ove protection.
- Are you SURE that the thermostat is operating correctly.
- Vent the block and make sure its full of coolant (no air)
- Proper pressure on the coolant system and the system HOLDS that pressure. Take it to a garage and have them pressure test the system if your unsure of its intergerity.

Im sure I missed something. Someone will back me up!



Bill

 

Good question... I was just thinking out loud when I said something about the temp sensor maybe being wrong...
HELP BILL...how does he verify the sensor is sending the correct temp to his gauges?

The dealership should be able to check the pressure of your system for you ... they will just pressure it up and make sure it holds the proper pressure.. I'm also not sure of what optimal operating pressure is...
HELP BILL... what is optimal operating pressure...i know the cap is rated to 18 lbs so it has to be less than that or it would be venting.

 

Do a compression test. You may have a blown head gasket between two cylinders. How is the performance? Anything dripping out of the exhaust? Just a thought. I had a blown 468 big block in a ski boat with a cracked cylinder that ran like a striped ape. But always ran hot. Just thought I'd throw that out. Rod

 

Is the pressure the same then if the temp is 190 or 230?

 

It becomes complex to get an exact pressure because elevation enters into the equation. But if we assume sea level....


No. It would be less pressure at 190 and more at 230. I would expect the pressure at 190 degrees to be nothing (atmospheric pressure in actuality). At 230 I would expect the pressure to be about 5 pounds (above atmospheric pressure) . At 250 degrees I would expect the pressure to be about 12-13 pounds.

 

Yes even changed the radiator :/

 

Thanks! Te performance is great, never an issue, nothing out of the exhaust, how can a compression test be done?

 

Clean radiator and condenser, good new thermostat, air dam properly placed, no air pockets, good coolant mixture, water pump works good too :/ thanks for you help! I will go and try to get a pressure test

 

This post concerning pressure test might help you:

https://www.corvetteforum.com/forums...sure-test.html

 

Exactly that's what I was trying to say but didn't know how to say it.. so, when they pressure test is it just for leaks or for actual pressure readings at X amount of temp/elevation etc. some formula for a "optimal pressure" similar to the "sweet spot" for temps.
And is there some way they check for flow rate to make sure the water pump is working properly?

 

I will be watching this to see what the fix turns out to be. As mentioned in previous post, the temp sensor may be bad. I would think U could change this yourself without having a pressure test done. I wouldn't think this sensor would be to expensive. With temp >230 U should be feeling some serious heat coming off the engine, have U felt this when U pop the hood?

 

Get a cheap Infrared temperature sensor gun like this one ($12 free shipping at Amazon). Same price range at Home Depot. Take a reading on a non-reflective component like end tanks. Accurate to within 5 degrees in my experience.

Amazon has the Nubee NUB-8380 Non-Contact Infrared Thermometer Digital Temperature Gun w/ Laser Sight for $17 - $5 off with coupon code 838N5OFF at final checkout = $12 with free shipping for Prime members or on purchases $35+.

 

I'll pop the hood but not any hotter than usual, I am going to a friends mechanic today hopefully he'll have an idea thanks for the input will keep you posted!