2001 tahoe 4.8l coolant flow / over heating

[LanceLyons]

Is there a way to make sure i have enough flow of coolant?
Can a water pump be broke and not leaking?
How much should a thermostat open at temperature?

My sons 2001 tahoe is overheats in a wierd way. It goes up to the 190 range for the thermostat and hangs there for about 30 seconds and then starts going up quickly from there.

I have burped this truck running it several times to thermostat temp for 5 10 min leaving the reservoir lid open.


I did pull the radiator and did get flow from top to bottom at a pretty good rate using hose. The clutch fan is good since it doesnt slip much.

Is there a way to make sure i have enough flow of coolant?
Can a water pump be broke and not leaking?
How much should a thermostat open at temperature?
are the flows on these tahoe's bottom to top (reverse flow?)

thanks in advance

 

[Fless]

Here's the bleed procedure from Haynes:



You might also want to feel the upper radiator hose to see if it's getting hot, indicating that the thermostat is opening.

Thermostat installed properly, with the spring end toward the engine?

Is the radiator clean and not plugged?

 

[LanceLyons]

Here's the bleed procedure from Haynes:

View attachment 260061

You might also want to feel the upper radiator hose to see if it's getting hot, indicating that the thermostat is opening.

Thermostat installed properly, with the spring end toward the engine?

Is the radiator clean and not plugged?

The thermostat is an integrated piece so it cant be backwards.

I did flush the radiator and actually pulled it out and cleaned / ran hose water through the top and noticed good flow out the bottom. Assuming this means its not clogged up.

Are the 2001 tahoes a reverse flow system. Does it feed the hot water in the bottom and it comes out the top of the radiator? Somebody had told me that.

 

[LanceLyons]

Do the 2001 Chevy Tahoe's have a reverse flow... that is heated coolant goes into the bottom of he radiator and out of he top?

One thing I noticed today while looking at it more.

I pulled the upper hose off the radiator and decided to add coolant mix straight into the upper hose and let it drain back into the motor. This time I was able to drive the vehicle around at least 20 miles and it never went above the 190 temperature.

before it would get to 190 and then within a minute shoot up to 230 plus.

This seems to make me thing there is some form of flow issue. (i have run through the coolant add procedure trying to burp the system some half a dozen times).

does this make sense?