I would be more than happy to look into this situation. Please private message me your name, address, vehicle identification number, and current mileage.

Thank you,

Jessica L.
GM Customer Care

 

What does the engine's temperature gauge report?

When was the dexcool last changed?

 

Temp is OK. Maybe a wee bit higher than normal.

Dexcool has 65k miles on it. Yeah, I need to change it.

 

You are thinking backwards. If it were a vacuum leak it wouldn't work under load as vacuum decreases proportionately with throttle opening. The more you hit the gas, the less vacuum. It should be highest at idle with the throttle closed. What you are describing is often caused by low coolant level, which at higher RPM moves enough around to provide some heat but at idle there isn't enough volume to provide heat. The elevated engine temp supports this also.

If that isn't it check for either a worn out water pump ( which shouldn't happen by 65000 miles) or a blockage that limits flow. As engine RPM increases the water pump spins faster and moves more coolant around thus providing more heat but at idle it cannot move enough due to either the limited flow or worn out pump.

Just my .02

 

You are thinking backwards. If it were a vacuum leak it wouldn't work under load as vacuum decreases proportionately with throttle opening. The more you hit the gas, the less vacuum. It should be highest at idle with the throttle closed. What you are describing is often caused by low coolant level, which at higher RPM moves enough around to provide some heat but at idle there isn't enough volume to provide heat. The elevated engine temp supports this also.

^^^ This ^^^

As well, if the above bares out, your system is probably full of scale and will need flushing.

 

I would think the car is low on coolant or has a air bubble trapped in the cooling system.
You can't rely on checking the overflow tank for coolant being "full" by sight on the
overflow tank on most new closed cooling system vehicles.

That because you mention the heat temp increasing when the engine speeds up.....................

 

Temp control is electric. Try unhooking battery for a while and it may reset, if not probably new motor.

 

Thanks, all.

Yeah, there did appear to be a bubble. I guess I didn't get the whole bubble purged.

 

Common...................

I see the same no heat/low heat posts on several GM truck forums that also have the closed cooling systems. Usually low on coolant or has a trapped air bubble and needs to be "burped"!

Glad it cured your problem...........

 

Well, it hasn't for sure, yet.

Gotta drop it off at the mechanic's sometime to have them give it a lookover. Gonna get the system flushed/refilled, too, since the Dex is from the factory fresh.

 

I wondered since they are self burping, the small hose to the reservoir is the air bleed.

 

Turns out there was a leak in a tee fitting under the engine and I was losing coolant.

I have heat, and no overheating issues now.

 

We are happy to hear the issue has been resolved! Please let us know if you ever need assistance in the future. We are happy to help at any time.

Jessica G.
GM Customer Care