Overheating

Used a combustion tester and the liquid stayed blue.

Checked cooling fans. The are running when the engine overheats - I checked this by getting out and listening or looking. Both fans will stay on when idling until the temperature gauge
goes down to normal then shut off - although sometimes the temperature will not go back down and the engine has to be shut off after idling for a while. The fans also stay on at high speed for five or ten minutes after shutting down the overheating engine. Cold air can be felt blowing.

Today I got a combustion block tester. I took the car for a drive and brought the temp up to normal. Used the tester at idle - fluid remained blue. Put the parking brake on and transmission in drive to bring the temp up above normal - fluid remained blue. When I shut down, the reservoir burped out hot fluid three or four times.

There is no residue on the oil filler cap or the reservoir cap.

With the engine at warm idle, there are no bubbles in the coolant reservoir as seen in your video. However, I do get burps of fluid when the reservoir is over full and the cap is off. I can squeeze the top rad hose easily and it feels like there are pebbles running thru it.

The engine runs smoothly with not even an occasional miss at a stop light. Purrs like a kitten at any speed and accelerates like a big-assed bird when I floor it - no hesitation.

Driving around town the temp will stay normal for a long but will eventually overheat if I drive long enough. Climbing hills brings the temperature up quickly.

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I do not have a shop or air.

Will take car to GM I guess.

Oops, I forgot, it was done previously by a shop along with a coolant system pressure test - no leaks.

Has overheated before tests and every day since all these tests in the last ten days.

Mechanic did a fluid test (which I did again with no yellow), pressure tested the coolant system - no leaks. Pulled plugs and bore-scoped for coolant - none, added shop air with no air bubbles into coolant. Mechanic very frustrated that he can't solve problem.

I keep thinking head gasket too but there just is no evidence.

Top coolant hose is hard but maybe the implore is slipping on the water pump once the system is pressurized, thus the flow is not enough.

It's a mystery so off to GM - the same folks who put in a new gauge cluster last week when no one else could.

I've heard aluminum heads disintegrate after a while due to steel contact, forget the term. Maybe?

Will advise. Thanks for your help.

If I need the heads replaced, who do you recommend for remanufactured heads? I'm in the Seattle area.

Went surfing looking for other solutions. Found www. Thermalweld. Com.

Spoke to Robert who says his product will fix my problem. Have you had any experience with them?