Mechanics

OVERHEATING

2007 Chevrolet Tahoe • 170,000 miles

Tahoe started overheating. Replaced thermostat, water pump, flushed the radiator twice, replaced the temperature coolant sensor, and checked to make sure the heads/head gaskets were good. They checked out fine. Truck is still slightly overheating. Need more suggestions.
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Fkmaples
October 9, 2013.




What size engine? 5.3? Also, have you verified flow through the radiator? You already replaced t. Stat, so next get the engine hot. (Operating temp around 215degrees) and grab the upper radiator hose. Is it hot? Next reach down and grab the lower radiator hose. (Engine off) is it hot also? If not, then your not getting flow through the radiator. I understand you tried to flush it. This doesnt always work. Let us know your results.

Madmike1735
Oct 9, 2013.
It's a 4.8. Will definitely check the hoses tomorrow! Thanks for the reply!

Tiny
Fkmaples
Oct 9, 2013.
No problem. I look forward to hearing back from you. Also, keep in mind this vehicle from factory with dexcool-its orange. Dont ever mix with green, as it will clump up, and clog everything.

Madmike1735
Oct 9, 2013.
Checked both hoses this morning. Flow is good. Not sure at this point what else it could be. Any more suggestions?

Tiny
Fkmaples
Oct 10, 2013.
How long does it take for it to start to overheat? And does it overheat at idle, or when your driving? You verified flow through the radiator, my next guess is that its airbound. When you turn the heat on, does it blow hot air from the vents?

Madmike1735
Oct 12, 2013.
Sometimes it overheats at idle and sometimes it does not! The heat does not blow hot when turned on. We are thinking there is air in the system. Does this sound the same to you. If so, what is the best way to get the air out?

Tiny
Fkmaples
Oct 12, 2013.
No heat from vent verifies my suspicion. It is air bound. Let me check to see if this engine has an air bleed screw. I dont think it does, but im going to double check. Have you checked the coolant level after you initially filled it up? Also, does your radiator have a cap, or do you fill your vehicle through the overflow tank?

Madmike1735
Oct 12, 2013.
After initially filling it up it settles and the coolant is a little lower but not empty and the truck does not have a radiator cap. We looked for an air bleed screw and either the truck does not have one or we did not find it.
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Tiny
Fkmaples
Oct 12, 2013.
Ok, your engine does have an air bleed nipple. However the picture im looking at isnt very clear. Its shows it should be near your oil fill cap on a coolant hose located towards the front of the engine, on the passenger side. Check it out. If you find it, what your going to do is fill the cooling system with the engine off. Open bleeder. When coolant comes out, without anymore air bubbles, shut the bleeder. Top off the system. You may need to get the engine up to running temp, then let it cool off and repeat this procedure.

Madmike1735
Oct 12, 2013.
Ok. We are going to look again. If its not on this truck, what do you suggest to get the air out?

Tiny
Fkmaples
Oct 12, 2013.

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