1998 Chevrolet Tahoe Vehicle Overheating

KNKNIF

MEMBER
1998 CHEVROLET TAHOE
5.7L
V8
4WD
AUTOMATIC
82,000 MILES

I have done the following so far:
Replaced:
-Intake manifold gasket
-thermostat (twice) also ran it without thermo, still overhearts
-Water pump (was leaking)
-Heater core bypass valve (was leaking)
-Fan clutch
-Radiator
-Radiator cap (twice. Not sure if the first replacement was defective or if my overheating broke it)
Burped the system (front end jacked) after each replacement. Latest time I burped for 1 1/2 hours.
Here is exactly what is happening (from a cold start)
Takes about 10(ish) minutes at idle to warm up to 200 (thermo is a 195) at which point the thermostat opens. If the radiator cap is on, it will continue to overheat to redline. If the radiator cap is off, it will not go past about 220-230 mark.
Notes:
no bubbles in the radiator
MINIMAL white smoke (some other guy said he saw it, I barely saw anything.
MINIMAL water coming out of the exhaust, seems normal as far as im concerned.
IM NOT A MECHANIC, totally possible I messed it all up.

3 Replies

KEN L

MASTER CERTIFIED MECHANIC
47,320 POSTS

Hello,

It seems there are a few things I can thing of that will cause overheating outside of the things you have already tried. The first is still a blown head gasket have you chemical checked the radiator? It could be blown even though no air bubbles are noticed, next, are you sure of the engine temp, did it boil over?

If not I have seen were the temperature sender can fail causing a false reading. On the outside, the cat converter can be plugged causing the engine to work harder, and lastly, check for air flow blockage in front of the ac condenser, these can become plugged up with dirt and road grim not allowing air to pass through, please check it out and get back to us :-)

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Saturday, October 25th, 2014 AT 7:42 PM

KNKNIF

MEMBER
2 POSTS

Blown head gasket - I have yet to do more extensive testing on that, so it could be that, I will test it when I can.

I am not sure how to verify the engine temp. Can I do this with an IR temp scanner? If so where on the engine would I test the temp?

How would I know if there is a block in the exhaust somewhere? Would I have to disconnect the exhaust before the cat?

Could you be more specific about blockage in front of teh A/C condensor? Specifically what do you mean?

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Saturday, October 25th, 2014 AT 7:49 PM

KEN L

MASTER CERTIFIED MECHANIC
47,320 POSTS

Yes, you can use an IR reader, here is some info on that, use it at the thermostat housing to test.

https://www.2carpros.com/articles/how-to-use-an-infrared-temperature-meter

You can test the cat using this method,

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

So you don't have to disconnect it.

Use a flash light to see if there is dirt stuck inside of the cooling fins of the condenser/radiator.

Sometimes its best to wash the front out using a garden hose on high pressure to see what kind of dirt comes out.

Please let me know what you find?

PS I am creating an article for the head gasket check but its on finished yet, but soon :-)

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Sunday, October 26th, 2014 AT 10:23 AM