Hello i have a 2001 audi a6 2.7t . I recently had the timing belt , watrer pump , thermostat done . Now when the car gets up to temp and im driving the heat blows hot hot , but as soon as i come to a stop the heater starts blowing cold . But as soon as i start going again it gets hot . My car never had this problem before . I checked the radiator fluid and its full . Any suggestions what could be causing this please let me know thanks

 

Does your water temperature gauge fluctuate? If so, then there is something wrong with the thermostat. Otherwise you may have air in the line.

 

no the gauge is fine its always at the half mark when fully warmed up

 

Open the coolant reservoir cap, run the heater to to high with temperature set to high. Run it for a few minutes and see if you can get the air bubble out.

 

ok i tried that but still blows cold at idle do you think i should take it in and have the radiator flushed ?

 

Having the radiator flushed isn't going to help you. If anything you should have the heater core flushed. It really isn't that complicated. There should be a DIY around somewhere that can walk you through it. You will need a little extra coolant to make up for the bit that you lose during the flush. However, I'm thinking that you don't have a heater core problem though.

If I remember correctly (someone help me out here) there is a vacuum control line that opens the line to the heater core. If you have a small vacuum leak the control line won't have enough oomph at idle to allow coolant to flow through the heater core, thus you get cool air at idle and warm air when the engine RPMs are up.

-or I could be completely wrong.

let us know when you get it sorted.

 

It makes perfect sense, Beau, since the heater blows hot while driving.
Obviously, everything else sounds like it's working properly. If the heater valve and/or the core were malfunctioning, then he wouldn't have had heat at all.

 

well tomorrow im going to flush the core and cooling system see if that helps hopefully some gunk is blocking the core a lil and the water pump at idle isnt enough to push fluid thru . like i said tho never had this problem till i got the t belt water pump and thermostat done last week

 

These are exactly the symptoms I'm getting with mine. Can anyone elaborate on the vacuum line idea? I've worked in heat exchange industry for over 30 years but its got me stumped. I've bled it, flushed it - everything works fine apart from blows cool below 2000rpm - fine above that.