Well, hopefully you have heat. I meant to say with the engine off pour coolant down the outlet hose and then through the inlet hose-then put it back together. then start the car with coolant cap ON....that's what I meant by a 'passive' system, coolant flow will increase with RPMs....When I do the bleed with the engine warmed up and higher RPMs, I leave my coolant cap ON while bleeding with high RPMs and just let the air escape through the little hole on the outlet hose.....and I don't raise the coolant tank ...everyone has their own way based on the original way. I just figure once I pour coolant down the inlet tube and it raises in the reservoir with the cap off, the only air left should be in the core. However, if you let off the gas with the little hole exposed, it technically will suck air back in.... I should've been a little clearer on that one.

AND, I had such a problem with a 2.8 once, that I built a little contraption with a Hot Water Heater relief VALVE to get the air out....didn't work very well. I also have an Audi's running with an Auxiliary water pump attached to make the heat work....no matter what we did, new heater core, vent doors, 2 thermostats etc...couldn't get heat out of it....so we got a 12v auxiliary water pump and heat works great now....and has been for 2 years....

 

Ok...I'm not sure what the hell is going on. Heat last night and now I don't have any. Granted it's slightly warmer than it was before last nights bleeding but it's not like it was before. Any ideas?

Last night around 7:00 PM:


Last night around 10:00 PM:


This morning around 9:00 AM:

 

Before all of this were you loosing any coolant at all? Minute traces of it? If the system is getting air into it at any point, tiniest of leaks, it will do this. I had one Audi with the tiniest head gasket leak, wasn't loosing coolant visibly etc, but no heat, or on and off heat while driving, once the head gasket was fixed, the heat came back and stayed...but it may have been unrelated and it fixed itself. But we fixed the head gasket because the test showed it was leaking and then the heat has been working ever since....I would do a compression check, or we use a UVIEW system to check for leaks, actually works quite well....didn't buy it from the link below, but what I came up with on a quick google search.....
Super price on UView 560000 at ToolTopia.com

OR, there is somehow still air in the system. As you are driving around, does the heat get better and STAY warmer, or does it come and go as you are driving? Are these readings all at idle? Or after a drive etc...

 

So I'm pretty sure there isn't a head gasket leak. I did a compression test this past spring/summer. It check out then, something like 170 across all except one at 165 (or maybe 175/170. I did my timing belt this fall and believe that's when the heat problems began. I suppose it still has air in the system at the very least.

 

So heat is there while driving for about 10 seconds then cold. Turn heat off heat for 2-5 minutes, still driving, and turn heater back on and I have heat again for about 10 seconds, then cold. Over and over again. Doesn't appear to be leaking. Picked up some coolant and am going to pour directly into core with funnel and down hoses to expel most of any lingering air, reattach hoses and attempt to blend out of outlet hose, with tank cap closed and tank attached (not raised.)

 

Well, so you turn the heat on, it comes out hot but then goes cold every time? And you are saying this is a consistant situation-happens every time the same way? So, it sounds like your heater core is trying to work properly...it could be something like a vent flap door or a bad cabin temp sensor telling it to blow cold...bad climate control system? Again, just throwing ideas out there.....

 

Thanks markymarc. So I filled the heater core directly through the core ends yesterday like described earlier. Then, with the cap on, hoses reinstalled, proceeded to bleed the core. I couldn't get a steady stream out of the bleed hole, but it was going much more than I have ever been able to get out of it. Of course, I had very little heat. I buttoned it up and proceeded to travel back home. During my travel, I managed to get hot/warm air for awhile, then shut if off because it's ridiculous to drive with the heater on when the outside temp. is above 70 (central California.) About an hour later I decided to see what I'd get if I turned on the heater. Sure enough, hot air for about 15-30 seconds then cold. It seems to be very unpredictable.

I think I'd be safe to say I'm getting the same results every time, it's just the detail have slight variances (duration of heat, warmth of heat when working, etc.) I replaced my g17 sensor months ago because of the faulty ambient temp reading. Although, as you might have guessed, that didn't fix that problem. I'm going go order g89 sensor this week and take care of that before I proceed. The problem is, my readings are faulty in the direction that should only aid in my (winter) heater issue. Meaning, with faulty low temp readings, that heater should be kicking on and providing hot air. This summer I was getting hot air when I needed AC because of the inaccurate temp readings. Yes, I have accessed the onboard climate control diagnostic codes. The only code, I think, I see is the 4.3 Fresh Air Intake Duct Temperature Sensor, sporadic open. I'll tackle that first then move back to the heater core if need be (I really hope not!!!) I've also reset the heater controls through VAGCOM, or whatever it's called...08 HVAC>Basic Settings>001>wait for 000. Do need to do that for any other group besides 001?

 

Does anyone know if something like this could be causing the problem?

 

No. There is no valve like that on a B5 Audi....and that is one shitty cocktail-napkin design.

I don't understand why you get little, if any, coolant out of the bleed hole. Makes me wonder if there is an obstruction, either in the heater core or elsewhere.