justincr250

long story.....

Had a tiny coolant leak and went cheap route by using Justice Brothers radiator stop leak. I know I should've fixed it the right way right away but money is tight right now.
Anyways - I now only have heat when in the RPMs. Have cold air when at idle. Here's what Ive done so far.

Car is cold - pulled back top hose leading to heater core exposing the bleed hole. Loosened screws holding reservoir down and raised the reservoir as high as the hoses would allow - filled the reservoir until coolant came out of bleed hole. Started car and let it come to temp with reservoir cap off to get any air out. Once at temp I gave it a few runs up in the RPMs. Still have cold air at idle. When in the RPMs the heater blows warm air.

Thought heater core was plugged so the next night I pulled both return and supply hoses off heater core. Hooked garden hose to the return side and let it run for about a minute. Gunk that came out didnt look to bad. Water was clear after the minute time. Hooked hoses back up and did the above steps and still get cold air at idle. It does feel a little warmer now when in the RPMs.

Wondering if any of you have any steps that I could try to get this issue resolved? Thanks in advance!!

Car is a C5 avant 2.8 (2000)

Airbag

i have a 2.8 with my Audi 90 . hve tried fixing this for about 5 years . even replaced heater core .. gave up and bought another car just for the winter.

audifirst

Could be your bad thermostat , did you had timing belt done ?
Second guess could be that heater core is plugged with the substance from the radiator stop leak

justincr250

I did the timing belt and thermostat about 10,000 miles ago. I originally thought it could be a heater core plugging issue also so that's why I flushed the core with a garden hose.

Airbag

let me tell you what i did on my car and the symptoms.. would blow cold on idle .. even when the temp on the dash shows warm.. the tmp on the dash would actually show colder on the highway due to the cooling of the rad but would still blast hot air that would melt you. hit traffic and have to stop and it would blow ice cold air within about 10 seconds if it is really cold outside.
i replaced 2 stats 2 water pumps all the coolant lines flushed it and flushed it to get any air out, replaced the heater core and eventually just gave up. i even tried putting in a auxillary coolant pump but still didn't fix it. \i have no idea what it is.

SloopJohnB@mac.com

Is it possible the heat issue is only on the driver's side? Does the passenger side behave the same way?

joshe8695@yahoo.com

I had same problem. Changed the heater core. Problem solved

Kris Hansen

It's air in the system without a doubt. My A4 does this all the time, not sure where the leak is, but even priming the core like you describe, I can not get it to circulate heat at idle either. I suspect there's an air pocket somewhere in the block or the hard coolant lines.. It's almost due for it's 180k timing belt service, hopefully I can get it to make good heat this time. =)

Airbag

I gotta telyou Kris that is what I did and it just didn't help. I wonder if I took it to a rad shop they would do something special to get the air out .. ? seams starnge that Audi has this weird issue ..

justincr250

SloopJohn,
Its cold at idle on both passenger and drivers side.