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CHECK COOLANT TEMP

Alright folks, it’s been a while, but I’m back. So here’s what I got. I flushed the heater core, replaced the thermostat, replaced the coolant temp sensor, the water pump is new, and I’m still getting the “CHECK COOLANT TEMP” light. People are suggesting to me that I have a head gasket problem. What do you guys think? I tested the thermostat with the hot water trick. I think I have eliminated the usual suspects. I still have cool air blowing through the heater. And yes, the hoses are hot..
 
To check head gasket you do compression test and check oil for coolant and coolant for oil as they can mix.

HOw is fan clutch?
IS this light on all the time or at idle or when city driving or highway driving?

Maybe install a Tee in one of heater lines and install a temp gage to double check.
 
Yeah with a head gasket problem the fluids may be mixing and you may be seeing bubbles in the coolant.

It may be time to get your local mechanic involved.
 
I'd be looking to confirm the accuracy of your temp sensor to make sure you're not chasing your tail with parts at this point.

if you're chasing a head gasket leak it's worth noting that there are testing kits available to test for combustion vapors in the coolant.

I've seen a number of mechanics using this very same device.

There are also some test strip based ones specifically for exhaust particles.

Those leaks are a lot harder to catch than the rest and unless your coolant is filthy, it's about the only type that id say can actually prevent adequate cooling. Oil in the coolant will reduce the effectiveness sure, but unless you're running brown coolant it's unlikely to be this bad.

I'm actually about to buy one of these myself as my tahoe drops it's coolant level over about an hour's worth of driving. The reservoir is also extremely pressurized. That said, the temperature reading on it is normal. I'd say it has a leak but it's managing to operate in temp despite it.
 
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