Ok guess im a "newb" but ive owened my b5 12v since oct of last year. Ive brought the car back from the grave over this past year repairing/restoring it to new.... long story short. My heat was starting to lack so i flushed my core and to no surprise it was slighty clogged. I opened a can of worms so to speak..... it didn't fix the prob. I then did t-stat water pump timing belt roller and tensioner pully. Also replaced my hard collant pipe bc the coolant bleeder was stripped out. All said and done ive bleed the coolant system to DEATH and i only have luke warm heat under higher rpms. So i flushed and reflushed my core in both directions. And not with a garden hose i have the air/water combo tool to do it properly and bled and bled the system pressurized and unpressuriezed still no heat. So i moved inside the car all my actuators or motors... ie. Blend door motor and flaps. All function properly in both directions. So i moved to
vaccum.. been needing to replace the lines any way... all replaced but one that i cannot fig out where it connects. The line runs under the heater core lines through the firewall and into the car but seems to disappeare. Where does it go? Cause i still have no heat... And what could i possibly have missed? SMH

Thanks in advance

 

Heater core is probably to clogged to ever work again. PIcture of the vacuum line? On my facelift car there are no vacuum lines running into the same grommet as the heater core lines.

 

I have great flow in and out of my core when flushing it. But barely any during the bleeding process. When everything is up to temp it will spew coolant from the bleeder on the outlet side but it will loose flow to almost nothing. Im trying to upload the pic of the vaccum line it wont let me do it from my phone it seems

 

From what I've heard when I had the same issue, A clogged heater core still flows. It just stays to the front of the core and doesn't flow through it so no lines blow if it clogs. I flushed and did the stuff you did and it worked. Where is your temp gauge at?

 

It goes to the vacuum accumulator that's between the HVAC box and the firewall. I believe that's only on pre-facelift B5's.

The bad news? You won't get to it unless you pull the dashboard out.

The good news? All the vacuum runs (what is it with the German love afair with vacuum?) is the fresh air/recirculation door behind the blower motor. It has nothing to do with temperature.

Here's a pic:

 

thanks for the diagram... well guess ill replace that vac line when i do the core. ive had a new core just dreading tearing my dash out. but it dont seem like i have a choice at this point.

thanks again guys

 

Give some serious thought to replacing your evaporator as long as you're in there. You have to evacuate all your R34 anyway....

 

aa-4

I've been going through the same problem with my 96 audi a4 and been pulling my hair out trying to solve my luke warm air issue. Replaced the water pump, thermostat twice, new heater core, system is fully bled, I have hot hoses, good flow, car comes to temp, and all door motors are fully operational...and still luke warm heat. Finally solved my problem last night. I have read numerous posts about solutions to the issue and have never run across what it took to fix it. When I replaced the heater core there were all kinds of foam pieces in the bottom of the heater core housing. In fact when I bought the used car, and I would change the air flow from the floor to the dash, bits of little black foam would blow out - almost a black dust. There must have been some kind of foam gasket around the blend door that would help create a seal and force the airflow across the heater core. The gasket must have completely deteriorated. The blend door motor is fully functional but it's travel length is no longer sufficient to create a seal, since the gasket is gone, which allows some of the air to bypass the heater core. It takes some pressure to force the air across the heater core so any little leak allows the air to sneak around the core. I disconnected the motor arm from the blend door arm, moved the door another 1/8 of an inch (upon inspection the arm looks like the door would be completely shut but all it takes is a tiny gap to reduce heat flow) and low and behold I have hot air...and now can cancel my reservation at the pysch ward. When I swing the blend door open and shut I can hear metal contacting metal. In my other 96 A4 this sound is a light thump, so I know there is something missing between the metal door and its contacting surface. My plan is to leave the arm disconnected for the winter season, in the hot mode, and reconnect it in the spring. Another option would be to fabricate something that would extend the motor arm just a little bit. It would be a good idea to fasten the door shut because it can move on its own a turn to cold air. This will happen when your wife is driving the car and you will hear about it. Don't know if this is your problem or not but I would definately give it a shot before replacing your heater core.

 

Never heard that one but it makes perfect sense. I hate to say it, but my 99 A4 has been pumping out some little bits of foam lately. Every now and then I see it on the dash, almost like foam "dust" just like you said.

Yet another option would be to pull the dash off and get back in there.

We might be neighbors MNaudifan. I'm in Eden Prairie.

 

Rochester. I don't think I will be "going back in there" anytime soon. It was quite the learning experience, and in hind sight I may have gotten by not doing it at all. The guy I bought the car from got rid of it because the shop told him the heater core was leaking. It was leaking, but from a split in the heater core pipe on the engine side of the firewall, not from the guts of the core. I bought a piece of heater hose the same diameter of the pipe, heated it in the microwave for 15 seconds (which was too long, holy crap was that thing hot) and slipped it over the pipe. Slapped a clamp on it and a brass hose mender barb to connect it to incoming hose and was good to go. Rear axle shaft a couple weeks ago, a couple front control arms, an outer front cv joint in October... I like the Audis but there are days I wish I did not know what I was doing and would have to go buy a new car. I think its just my stubborness proving that I can keep a 17 year old car operating on my own.