01 Yukon Denali Getting Hot

[aaford72]

Thanks in advance for any thoughts:

2001 Yukon Denali 6.0 - first noticed an issue with getting hot when temps outside were over 85 degrees and AC was on. When AC turned off and heater turned on temp would go back down. I had coolant system flushed, new thermostat, new fan clutch all done (a different times) trying to figure out what was causing this. None of these things worked.

Two days ago I was driving up the road and had a plastic fitting that attached to the heater core near firewall break in half and blew the coolant everywhere. Replaced the fitting and got it sealed back up, replaced coolant and then the battery died. Jumped and drove home. Charged battery and that was ok.

Driving today to test things out the temp started climbing after about 15 miles on interstate without AC on. Outside temp was 95. Turned on heat and temp came down to normal. Brought home and parked it.

What do I do next? What should I be checking?

 

[ali saleh]

New radiator most likely will solve that heating issue

 

[M1Gunner]

I don't know your usual driving routes but you're radiator could be restricted. Air flow wise.

You could also, if you think your radiator may be restricted internally, drain the system and pour a bucket of water through it and compare the amount going in to what's coming out.

You're water pump may not be operating as intended. Any unusual grinding or chatter at idle?

By turning your heat on during highway operation utilizes your heater core as radiator essentially. So it's possible it may just need a good hosing down. Not to mention, if the heat is blowing in the truck then you have coolant flow within the system. So thermostat is opening and etc.

 

[bottomline2000]

I'm betting waterpump. Should be considered a maintenance item after 100k miles.

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[Tonyrodz]

Look at your radiator around the side tanks and the bottom that rests on the radiator support. See any seepage or other stains? Any type of corrosion on the bottom? Also notice a coolant smell or any on the ground? Crawl underneath, any seepage under the water pump?

 

[retiredsparky]

Older vehicles should gradually get certain parts replaced before they fail--one of those parts is the water pump. Even if that doesn't fix the problem, it will often prevent a later break down.

 

[RED TAHOE LS]

Aaron, as OP have mentioned replacing the radiator, it's probably time. Before doing so, you can check it by checking the difference between the upper and lower radiator hose with engine @ operating temperature. If the upper hose is hotter than the lower, replace the radiator. What ever you do, make sure your overflow tank will hold a constant level, if not, find the leak.
Often overlooked is the radiator CAP, you can go to Autozone and use their tester to check it. Good luck and keep us posted.
David g...........

 

[Danny3737]

It could be that your thermostat is not fully opening

 

[bottomline2000]

Aaron, as OP have mentioned replacing the radiator, it's probably time. Before doing so, you can check it by checking the difference between the upper and lower radiator hose with engine @ operating temperature. If the upper hose is hotter than the lower, replace the radiator. What ever you do, make sure your overflow tank will hold a constant level, if not, find the leak.
Often overlooked is the radiator CAP, you can go to Autozone and use their tester to check it. Good luck and keep us posted.
David g...........

We don't have radiator caps..only the cap on the surge tank. He would hear the pressure release after the truck was run and it's unscrewed. The difference in hose temp could be from a lack of flow i.e. water pump. You could always run some distilled water thru the radiator and see if it's clogged. $1/gallon.

It could be that your thermostat is not fully opening

He's already replaced the thermostat.

If the truck is getting up to temp, thermostat is opening (check lower hose) then the only thing left is flow or lack of. Either the radiator is clogged or water pump is bad. If you Rev the engine and the Temps drop I'm willing to bet on the water pump losing its efficiency.

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[M1Gunner]

If heat is coming from the dash then you have coolant at least some flow and the thermostat is operating.

And as for the cap, the cap on the Surge tank could be defective but you won't over heat until you lost a substantial amount of coolant. Which your low coolant light would come on and warn you before you lost enough to overheat.