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Heater works while accelerating, blows cold when release gas

My 2003 Buick Century heater works fine while accelerating but as soon as I release the gas the air begins to cool, swiftly. I have had the radiator flushed and the coolant topped off but the problem persists. Any ideas?

The Cooling System Was Flushed And Topped Off To Remedy The Heat Problem ?
Was The System Low On Fluid Prior To This ?
Was The Cooling System Pressure Tested At That Time ?

Recheck the coolant level, again. Check in the recovery bottle and if it has a radiator cap, the radiator.

I think it’s possible that you’ve got air getting in your “closed” cooling system (and coolant getting out). This can happen externally to the engine or internally.

Some of these vehicles had problems with intake manifold gaskets leaking. Check your oil for condition. It should look like oil and not creamy beige (mixed with coolant).

Who flushed the coolant ? I’d take the car somewhere where the people working are familiar with the topics that I’ve discussed, here.

CSA

While I would agree with CSA, the problem’s most likely coolant level, do you have any issues with the engine getting hotter than it’s supposed to be? If you’re having overheating issues on top of the heater problem, the impeller on your water pump may be getting worn and need to be replaced (the whole pump, not just the impeller).

Chase

I would also bring up yet a different possibility that has nothing to do with the cooling system itself. Rather, I’d guess that you are having an issue with your blend door. This is in the ductwork and controls the air path in the ducts. Many of these are vacuum controlled, and the engine vacuum varies as you do thing like accelerate. I used to have a Caravan where the air went to floor vents anytime you accelerated, no matter where the position was set. It would go back to where you put it after accelerating. I’d start by looking along the firewall for a disconnected or damaged vacuum line. If nothing is found there its time to go fishing under the dash.

Of course, it might also be that your blend door is solenoid controlled in which case I’d be tempted to ignore what I just said.

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All the McParts stores sell a Prestone flush kit that includes various sized couplings to allow attaching a garden hose to a heater hose. Those adapters make great bleeders for the cooling system. Installed in the highest point in a heater hose, top off the radiator, start the engine (cold), loosen the cap on the adapter and watch for coolant to dribble out. The air will be gone.

I interestingly had a similar problem, it ended up fan speed 1 and 2 were burnt out on the variable resistor, a quick easy cheap fix.

Previous Comments:
“Rather, I’d guess that you are having an issue with your blend door.”
" I interestingly had a similar problem, it ended up fan speed 1 and 2 were burnt out on the variable resistor, . . . “
“I think it’s possible that you’ve got air getting in your “closed” cooling system (and coolant getting out).”
” . . . the impeller on your water pump may be getting worn and need to be replaced . . . "

Courtney Says, “My 2003 Buick Century heater works fine while accelerating but as soon as I release the gas the air begins to cool, swiftly.”

Not enough information is leading to guesses. I feel we need some clarification from Courtney. I took her comments to mean that the fan and its functioning were working correctly, but the air temperature was the problem, here.

Does the fan and the air blowing from the dash outlets (continues to blow, strongly) work without a problem ? Is it only the temperature of the air that changes with accelerating/coasting ? Please explain.

CSA

It sounds like there is a problem with the cabin temperature. Possibly the blend door is out of whack due to a vacuum leak that is causing the door to open or close at the wrong time.

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To: AlanY, Thank You !
From: The Department Of Redundancy Department

Three days ago, Cigroller suggested, " Rather, I’d guess that you are having an issue with your blend door."

CSA

The blend door might act up when accelerating due to low vacuum but not when letting up (high vacuum). I think it is low coolant level and would follow Rod Knox ecellent suggestion or unbolt the overflow jug and hold it high to let air out of system.

I puzzled over that since it is a little bit backwards. What I would actually surmise is that there is a vacuum line that split someplace and leaks only under relatively high vacuum - as in when the throttle snaps closed.

Low coolant doesn’t fit either if it cools “swiftly.” I guess it depends on how swiftly it cools. Even if the heater core isn’t being fed enough hot coolant, or if it is restricted, the effect won’t be “swift” - it would be gradual. The problem apparently didn’t change after cooling system service either. Perhaps the OP might return at some point and provide more complete info. Or perhaps this will be yet another thread where the OP never returns.

deleted

I am going to finally bring the car in tomorrow to have it assessed by a mechanic. Sorry if I wasn’t clear in my description. The fans work fine in the car, the air is blowing as it should according to the level that I have it set on. It doesn’t matter the setting (low-med-high) or whether I have set to defrost or floor or both. When I am actively pressing on the accelerator, the air is hot/warm, as soon as I release the accelerator, the air is cool, not gradually cool, immediately cool (this is very easy for me to identify now that it is below freezing in Minnesota). The car is NOT overheating. the engine temp stays appropriate.

It doesn’t seem that there is an air bubble in the coolant, I have checked the radiator and overflow levels several times and they are unchanging. I am definitely not leaking coolant. there is not coolant visible in my oil. I have no idea how/where to check “blend door”

Sorry I neglected to come back after reading the comments on the 15th. I thought I’d come back and read them again before going to the mechanic tomorrow so I at least felt slightly educated (lol). Thanks:)

I am guessing a restricted heater core; let us know.

I a way, it sounds like a vacuum problem, but it acts just the opposite of what I would expect.

YOU HAVE AN AIR BUBBLE IN THE COOLING SYSTEM!!! Cool air at idle followed by hot air at acceleration is normally air trapped in the system. This vehicle MIGHT have a bleeder for this purpose.

It doesn’t seem that there is an air bubble in the coolant, I have checked the radiator and overflow levels several times and they are unchanging…

The levels won’t change since the air is trapped back towards the core.

Besides a bubble in the cooling system, it could also be the coolant pump.

You’re not blowing white-ish smoke out of the exhaust, are you?
Just asking this because the problem you describe along with blowing smoke is a very common issue with the Nissan Altimas.
It very often is related to the head gasket.

If it reacts quickly to the throttle I’m guessing blend door/vacuum leak, rapid temp changes wouldn’t happen because of a bubble or other problem with the cooling system.

I am having the same problem with my ford focus2010. As it idles the heater blows out cold air when I accelerate it stays warm as long as its being accelerated. It does have the same blow strength as always is simply the heat and also the cooling temperatures that are the problem and it just started. My chrysler 300 2007 has had almost the same problem for 3 yrs. No one can tell me what it is. Do all vehicles do this eventually?

No…