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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?
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  • edited November 2011
    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.
  • 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.
  • edited November 2011
    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.
  • 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.
  • edited November 2011
    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.


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