Heat gets warmer on acceleration, cooler at idle

[MintyFresh]

The heat is not as hot as it should be at idle (but it's still warm so I am getting heat), and gets hotter on acceleration.

I flushed the coolant system twice with a cleaning agent, also disconnected the heater core and reverse flushed that. Replaced the thermostat as well. Still didn't help.

What next, replace the water pump?

 

[Celeborn]

The reason it gets warmer while accelerating, is due to the engine working harder, and heating up more. I don't think the water pump would have any effect on your heat, unless the pump was failing, but you'd have worse problems on your hand if that was the case.

Is the air flow normal, or is it possibly restricted?

 

[MintyFresh]

The reason it gets warmer while accelerating, is due to the engine working harder, and heating up more. I don't think the water pump would have any effect on your heat, unless the pump was failing, but you'd have worse problems on your hand if that was the case.

Is the air flow normal, or is it possibly restricted?

Air flow is also bad (only on some vents), however I think that is due to the fresh air door is broken. That is also getting fixed this week.

My thoughts were that at higher RPMs the water pump is pumping faster, thus giving more heat. Maybe the fans are worn down on the water pump

 

[silverfox103]

I have a 2003 Aviator that I had a similar problem. I flushed out the heater core which helped some. I then bled the system of air. That took care of the problem. Have more heat than I know what to do with now.

Tom

 

[MintyFresh]

I have a 2003 Aviator that I had a similar problem. I flushed out the heater core which helped some. I then bled the system of air. That took care of the problem. Have more heat than I know what to do with now.

Tom

lucky SOB!!

 

[rocco123]

Throwing this out there.... not enough vacuum to open the heat control valve at idle?

 

[MintyFresh]

Throwing this out there.... not enough vacuum to open the heat control valve at idle?

That is a great suggestion. After some research I think you might be onto something. definitely going to check that out tonight. She's at the shop right now getting new tires/alignment

 

[Number4]

Def a vac issue. At idled you'd get warmer air otherwise as the car doesn't cool as efficiently when stopped.

 

[TechGuru]

Throwing this out there.... not enough vacuum to open the heat control valve at idle?

Thing is there is more vac at idle than under acceleration.

I think it's a coolant flow problem.

 

[FordGT55]

To be sure it is not your heater core drive your explorer around and get it to operating temperature. Stop in your driveway / parking spot and with your heat on high put your hands on the heater core hoses. Both should be hot to the touch and you might not even be able to grab them long. If your heater core is restricted one hose will be hot/warm and the other warm/lukewarm. Even if both are hot it could still be a flow issue through your heater core only on VWs or Audis with the plastic water pump fins have i seen it be a water pump unless the water pump was already failing.

 

[lincolnshibuya]

your coolant might be still low, did you add more on the degas tank?

 

[mbrando1994]

This may sound crazy, but I do remember reading this somewhere. Check your radiator fan shrouds. If one is loose/missing it can cause issues with airflow. Not sure if it was pertaining to this issue or if it pertains to all models, but worth a check nonetheless. Edit- I did find where I read it and it pertained to cooling not heating, I am pretty sure it could apply either way. I'd definitely check it out first since it could be a simple fix.