2000 Tahoe Overheating?

I am not sure if my 2000 Tahoe (5.3L V-8) is actually overheating or not. Driving around town, temp will be in the normal range, then go up to around 225 - 235°F for a couple of minutes, then right back down to normal (< 200°). I have replaced the water pump (had the gasket leak) in the past few months, and just replaced the thermostat hoping that would fix the problem. I don't think that it is a head gasket, no bubbles, no sludge, no coolant loss. Could it be the temp sensor heading south? Also, I did add green antifreeze when I changed out the thermostat. Local auto parts place was out of Dexcool, and this Prestone said it was an extended life antifreeze and compatible with all antifreeze, even Dexcool. Any ideas would be appreciated. Thanks.

I am not sure if my 2000 Tahoe (5.3L V-8) is actually overheating or not. Driving around town, temp will be in the normal range, then go up to around 225 - 235°F for a couple of minutes, then right back down to normal (< 200°). I have replaced the water pump (had the gasket leak) in the past few months, and just replaced the thermostat hoping that would fix the problem. I don't think that it is a head gasket, no bubbles, no sludge, no coolant loss. Could it be the temp sensor heading south? Also, I did add green antifreeze when I changed out the thermostat. Local auto parts place was out of Dexcool, and this Prestone said it was an extended life antifreeze and compatible with all antifreeze, even Dexcool. Any ideas would be appreciated. Thanks.


compatible antifreeze is not to be used with dexcool...only dexcool or a coolant that states it is GM approved !


this coolant you used is not compatible with dexcool..you will see that it does not have any statements stating dexcool ..

this would indicate a possible problem as things will corrode and get black goop growing ....

it appears you have a corroded system anyhow because of the work you described ....dexcool with distilled water with at least 50%...

on your vehicle that means you need 2.5gals of dexcool if you drain the radiator/heatercore/and engine...total capacity is about 4.25gals..


after any work on the coolant system run the engine with the coolant cap off until it hits the 195/200deg f temp rev a few times ..this will get the air out...must not have air in the coolant with dexcool.. good luck ..

OK - an update. Per the folks at Prestone, their extended life antifreeze is indeed compatible with Dexcool, it does not contain any silicates, like the regular stuff does. Also, from a TSB released by GM, the big danger in mixing regular green antifreeze with Dex is that you no longer have extended protection, and the consumer may object to the brown color of the mixed antifreeze. The only mention of sludge that I can find on the GM site is what we all know, when Dex has air trapped, it will tend to sludge up.

That being said, I am still having an issue. Only when the A/C is turned on, it will sometimes read hot (220 - 225°F), then it will go back down to normal range. If the A/C is not turned on, I can drive it hard all day and the temp never even gets to mid-range on the gage. Any ideas?

OK - an update. Per the folks at Prestone, their extended life antifreeze is indeed compatible with Dexcool, it does not contain any silicates, like the regular stuff does. Also, from a TSB released by GM, the big danger in mixing regular green antifreeze with Dex is that you no longer have extended protection, and the consumer may object to the brown color of the mixed antifreeze. The only mention of sludge that I can find on the GM site is what we all know, when Dex has air trapped, it will tend to sludge up.

That being said, I am still having an issue. Only when the A/C is turned on, it will sometimes read hot (220 - 225°F), then it will go back down to normal range. If the A/C is not turned on, I can drive it hard all day and the temp never even gets to mid-range on the gage. Any ideas?

the fact still remains , those mixing with other coolants get the sludge and overheating....

nowhere on this prestone compatible coolant CONTAINER does it say DEXCOOL ! Or any statement stating this is the same as DEXCOOL ..

SLUDGE is created when organisims start growing in the coolant...
air,minerals,chemicals used IN drinking water or in ground water feed these sludge creating organisms...distilled is required to keep the system free of blocking /coating of the metal passageways...

the 15 min acid flush must be used to remove all this damaging film ..

if your coolant system has no black growth , remove the thermostat to insure the metal looks like alum...if clean then replace the fan clutch ..

I won't go into the green stuff vs Dexcool as I always stick with Dexcool. So with your temp gauge indications going up and down, as you posted, there may be air in the system causing this.

Can you hear a fan kick in that brings the temp back down to normal?

Running the A/C will for sure increase the coolant temp as the evaporator core dissipates the heat in front of the radiator.

With that said, maybe you don't have an issue at all?

Not sure why I never replied to this thread, but here goes now, maybe it will help someone else.
Turns out it was the radiator itself. With the engine running, I could watch those wonderful plastic tanks on the radiator almost "breathe" and see coolant barely seeping out through the plastic. New radiator installed, all the overheating issues went away. Glad I saw it before I had a catastrophic failure.

Not sure why I never replied to this thread, but here goes now, maybe it will help someone else.
Turns out it was the radiator itself. With the engine running, I could watch those wonderful plastic tanks on the radiator almost "breathe" and see coolant barely seeping out through the plastic. New radiator installed, all the overheating issues went away. Glad I saw it before I had a catastrophic failure.

good to post back that you had side tank leaks on radiator. with low coolant pressure the higher the elevation the vehicle operates the quicker the coolant will boil .water pump pumps water not air . so temp surges will occur .

still I disagree with the coolant used never mix NON GM approved dexcool with other coolants and only use distilled water .
if it was compatible it would clearly state GM dexcool compatible !
phone reps are NOT tech's.

still working 6 yrs that is good.