allman7062000

my 02 vette continues to overheat..i have replaced the thermostat..coolant..removed the cooling fans and cleaned the radiator and condenser..it's still overheating..suggestions?

dgrant3830

When you turn on the AC, do the fans operate normally? They should be on when the AC is on, if not, thats where the problem starts. Finding the cause is another matter, but not hard. Check to see if they are running.

corvettedoug

What did the coolant that you drained look like? If it was the dexcool and looked like brown sludge, then you might have to do a more thorough flush, or boil out the radiator.
I had to do that for an 02 blazer a couple of years ago when my dexcool got air in it and turned to sludge

BlackZ06

This is your first post ... welcome to the forum .....

First - what do you call "overheating" .... these cars will run engine temperatures of about 230 degrees when sitting in traffic.. People that aren't used to this are afraid the car is "overheating".

If you are seeing higher temperatures than about 240 then that does indicate a problem. As dgrant3830 suggests, check that the fans are working. They should come on in LOW speed with the car sitting still and the A/C system on. If that works, continue to idle the car, turn OFF the A/C, and at about 226 degrees the fans should come on in LOW speed mode. At 235 they should both switch to HIGH speed mode (there is a momentary period when they switch where one runs LOW and one runs HIGH).

If the fans are working OK, and your coolant temps are still hitting 240 or higher, you're probably looking at one of two problems ... a blockage in the cooling system (probably the radiator) or a water pump that is not moving coolant correctly.

Again, welcome,

allman7062000

coolant looked good...fans are working properly....temp going to red..250..35,000 mi car....

ART RAHN

HAVE SAME PROBLEM 1991 VETT 32000 MILES I HAVE DONE EVERYTHING. FLUSHED SYSTEM, NEW THERMO, CHECKED FANS, CHECKED WATER PUMP, etc. hope someone out there can help us. take care.

BlackZ06

Here are the steps (edited) listed in the Service Manual .....

1) Inspect for missing/damaged radiator shroud and air dam. (replace as neccesary)

2) Inspect for loss of coolant (replace as neccesary)

3) Inspect for correct coolant/water mixture (replace as neccesary)

4) Inspect pressure cap on overflow reservoir for correct operation (replace as neccesary)

5) Inspect for faulty Engine Coolant Temperature (ECT) sensor (see DTC P0117, P0118 or P0125) - (replace as neccesary)

6) Inspect for cracked/damaged overflow reservoir (replace as neccesary)

7) Inspect for cracked/damaged/collapsed hoses (replace as neccesary)

8) Inspect serpentine belt for correct tension and operation (replace as neccesary)

9) Remove water pump - inspect for damaged water pump driveshaft (replace as neccesary)

10) Inspect for blocked air flow to radiator - check area between the A/C condensor (forward of radiator) and radiator for blockage.

11) Inspect for blocked cooling system passages

12) Inspect for inoperative cooling fans

13) Inspect thermostat for correct operation (replace as neccesary)

14) Inspect for correct radiator installed - (replace as neccesary)

15) Replace radiator

allman7062000

thanks...i have checked everything but the waterpump..i drove the car for two days and all was fine but the third day overheated again...i'm not sure how the pump goes bad but it seems to be flowing coolant..no leaks..no noise...well...i haven't checked the sensors but i don't know where they are..and thanks for the reply

corvettedoug

The list above is very thorough, you should be able to find your problem after it.
You can test the resovoir cap with a coolant pressure test. You can rent for free from Autozone.


I did find it interesting that a step to check for blocked passages, but how would you do that without taking everying apart? Maybe they meant to use a heavy duty flush solvent.
Good Luck with your problem.

BlackZ06

I suspect (haven't tried it) that one of those Infrared thermometer "guns" would come in handy for this. The water flow in an LSx engine is from the bottom of the block up and then through the heads. Possibly with a gun you would find a "hot" area in one of the heads if a cooling passage was blocked.

The gun would also be useful for seeing temperatures at certain points in the system. For example, starting with a cold engine, you could watch the temperature of the hose flowing coolant to the radiator. Initially it should be "cold", and stay cold until the thermostat opens. Watching the coolant temp on the dash .... when the coolant hits 195 (stock thermostat) the hose temperature should rise rapidly. If it is slow, and the dash is showing rising temperatures, then the thermo or water pump is not doing its job. The coolant isn't getting to the radiator efficiently. If you've already eliminated the thermo and pump, then the radiator is blocked.

If the coolant to the radiator quickly gets "hot", then check the hose returning coolant to the engine. If there is little temperature difference between the two hoses .... then the radiator is not doing its job.

Point is, you can probably figure out a lot using a thermo gun. It could even tell you if the ECT sensor is working correctly, cause if the gun shows the coolant at a completely different temperature, then the sensor needs replacing.

dgrant3830

Sounds like you have either a plugged up coolant system or your radiator and condensor aren't totally cleaned out yet. Yes, you said you cleaned them, but maybe not enough. I've never had my thermostat out yet, but having said that, can it be installed backwards?

LV Vette

Can't be installed backwards. The thermostat is part of the inlet. Remove it and you will see what I mean.

Wish I could help more, but I think the others covered about everything.

Clayton from Las Vegas

TEXHAWK0

The thermostat is not actually part of the inlet housing. It is a tight fit with a rubber gasket around the edge of the thermostat, but it can be removed. However, if you did not know it could be removed and never took it out, then that is not the problem

BoostIt?

I've heard of clogged catalytic converters causing an overheat issue before, not specifically to the C5s tho. A tank or two of skunk gas and viola....

js23n0b

I am currently having the same exact problem with my '02 but I think that I have it figured out. Everything in my system is spotless clean, good pump, free flowing radiator, new t-stat, good fans, and no sign of head gasket issues. So my last thought was to check the two 3/8 fittings on the top right radiator. These fittings are inlet and outlets for a self bleeding sysem. If one gets clogged, either the block or the radiator will not be able to release air pockets that can develope. I checked the outlet side and sure enough it was completly clogged so I shot some high pressure air through it and heard a chunk blow out. If the right side of the radiator holds an air pocket it will not allow the water to pass through completely and that's what was happening with mine. Only one section would get hot and the rest was cool to the touch. Hope this solves your problem, let me know.

T VETTE

rgtkst

is it only while sitting still in traffic or driveway?? or while moving at a fair rate of speed also?? these answers would help detirmine if its an airflow or water flow problem
and did you check to make sure the t-stat opened as it should before the install of the new one. i had a brand new one not function correctly on me on a car several yrs back. easy way to tell is to put it in a pan of water on the stove and watch for the temp it opens at as the water heats up.

LV Vette

Oh, I forgot to ask. Do you have a big front mount intercooler? If so, that may be the problem.

Just an idea,

Clayton from Las Vegas

RED99

The engine coolant sensor is on the driver side head on my car, near the front exhaust bolt, under the alternator.
I would get a new cap, and sensor, since these are easy to replace and low cost. That will eliminate those two possibities.
As someone mentioned above, if the cats go to crap, they can cause a plugged exhaust system and cause the motor to run hot.