No heat while car is warming up

[Tahoe97]

Back again with 2005 Tahoe issues. When we are warming up the car before driving during these cold mornings in NC, the heater is blowing cold air even though the temp gauge shows the engine is warm. Not until we start driving does warm air start flowing from the vents. In addition to this the electric engine fan seems to be running more than normal. The last time the latter issue developed we were advised by GMC that we were low in coolant due to a leaking water pump so they replaced it (2021 repair). Is it possible we are low/losing coolant again and this may be the reason we have cold air coming from the heater vents after the Tahoe is warmed up but before we start driving? Getting expensive to keep all systems running now at 286,000 miles. Thanks!

 

[Fless]

I recommend checking the coolant level and topping off as needed. If the coolant is orange, it's probably DexCool.

You might also need a new engine coolant temperature (ECT) sensor, but that needs to be diagnosed.

 

[iamdub]

Back again with 2005 Tahoe issues. When we are warming up the car before driving during these cold mornings in NC, the heater is blowing cold air even though the temp gauge shows the engine is warm. Not until we start driving does warm air start flowing from the vents. In addition to this the electric engine fan seems to be running more than normal. The last time the latter issue developed we were advised by GMC that we were low in coolant due to a leaking water pump so they replaced it (2021 repair). Is it possible we are low/losing coolant again and this may be the reason we have cold air coming from the heater vents after the Tahoe is warmed up but before we start driving? Getting expensive to keep all systems running now at 286,000 miles. Thanks!

Sounds like air in the system, which is what happens when the coolant is low. The engine revving while driving circulates the coolant which replaces the air in the core, giving you heat.

 

[MassHoe04]

Agree with first looking at coolant level being low. Check that first.

 

[Tahoe97]

Agree with first looking at coolant level being low. Check that first.

Checked coolant level. That is it. Very low. Must be losing coolant somewhere as the water pump was replaced by GMC in September and coolant topped off at that time.

 

[MassHoe04]

Mine was low and I was worried about the same thing... Leak? I topped off and is holding steady. I just bought mine in October. I think there may have been some work done on it beforehand, involving thermostat or maybe water pump.

My theory is that coolant drained out of the system and the rear heat was not full to capacity. My topping off the reservoir seemed to improve the consistency of heat coming into the cabin now. Level is holding steady. Oil is not milky and no unusual amounts of vapor at the tail pipe.

I think the rear heat burped out the air, drew in more coolant to fill the void in the back and that caused the fluid level up front to drop.

Since I topped off, everything seems good.

Could be similar situation with yours or others after work had been done involving cooling system components.

Good luck!

Let us know what happens.

 

[Tonyv__]

Same here my 00 had low coolant 1 time in the 5 years I’ve owned it. No obvious leak. No recent work done. Heat did the same exact thing. Topped it off and kept an eye on it. Never went low again and the heat worked great. Weird if you ask me. But maybe a ton of air was trapped in the system for a long time and finally “burped”

 

[Fless]

Well, I don't want to sound like a jerk, but you might want to check the coolant more often than every 5 months, or just when problems arise. Once a month might be a better interval so you can monitor coolant loss, if there is any. Another possibility is maybe the dealer didn't get it quite full and burped when the work was done last year.

The fluids in these vehicles are their lifeblood; for the sake of longevity it's a good idea to check them regularly, and exchange them at the appropriate intervals.

 

[Tahoe97]

Well, I don't want to sound like a jerk, but you might want to check the coolant more often than every 5 months, or just when problems arise. Once a month might be a better interval so you can monitor coolant loss, if there is any. Another possibility is maybe the dealer didn't get it quite full and burped when the work was done last year.

The fluids in these vehicles are their lifeblood; for the sake of longevity it's a good idea to check them regularly, and exchange them at the appropriate intervals.

Well, I don't want to sound like a jerk, but you might want to check the coolant more often than every 5 months, or just when problems arise. Once a month might be a better interval so you can monitor coolant loss, if there is any. Another possibility is maybe the dealer didn't get it quite full and burped when the work was done last year.

The fluids in these vehicles are their lifeblood; for the sake of longevity it's a good idea to check them regularly, and exchange them at the appropriate intervals.

I welcome all suggestions. I believe I will take the advice of adding coolant and go with the theory that air was in the system from the Sept water pump replacement. Then I will keep an eye on the level routinely to see if it declines. I would welcome recommendations on coolant to add assuming the GM coolant is already in there. Thanks!

 

[rockola1971]

I welcome all suggestions. I believe I will take the advice of adding coolant and go with the theory that air was in the system from the Sept water pump replacement. Then I will keep an eye on the level routinely to see if it declines. I would welcome recommendations on coolant to add assuming the GM coolant is already in there. Thanks!

Me personally...Anytime I buy a used vehicle that has Dexpuke in it, I drain it and put in the tried and true Green antifreeze (Ethylene Glycol). You ever seen what happens when Dexpuke gets air mixed in with it or some numbskull adds the green to it? And anytime you have a problem with the cooling system its because there is a leak somewhere and AIR gets introduced into it. The Dexpuke looks like someone puked chunks into your radiator which plugs the core all up and who knows what other passages in our LS based engines.