I have a 2001.5 A4 1.5T Quattro bought in 2001.5.
This fall the heater has not been very warm. In November I took the car to the dealer complaining that sometimes there was heat and sometimes not (or very little). Their solution was to flush the cooling system. Seemed to help at the time, but then it was hot, not hot, hot. Mostly not hot.

I took it in a second time and they suggested the heater core should be replaced. Expensive. I chose to be cool, cold actually.

Today was -14C and windy. Bloudy Cold!!! I noticed that there was more heat when the engine was reved, and under load. I also use the "magic codes" on the radio to look at water temperature which was for the most part normal at 92C except when I was idling where it went "up" to about 95C.

Might I have a problem with my water pump? The idea occurres to me since I had the pump replaced at about 90,000km when the timing belt was changed. Also the thermostat. Could it be starting to fail??

Do my symptoms sound like a waterpump or a plugged heater core??

Does anyone know of a recall due to waterpump issues?

The car has 130,000km on the clock and otherwise looks and runs like a dream.

I intend to sell this beauty in the spring because I have no confidence the dealer can diagnose and repair these age related mechanical issues which recently have become more common. (I also have concerns about the airflow control dampers)

Please let me know your thoughts and comments.
Barry

 

Getting more heat when revving indicates air in the heater core which will need to be bled.

 

Thanks
Could it also mean the core is partially blocked?

 

To my way of thinking, no. Low heat regardless of engine speed would suggest blockage but heat increasing with RPM spells out a bubble. Heater core portion of the coolant pathway is a passive section and in parallel with the rest of the system (some coolant diverts to the core and later reenyers the main part of the system). It's low volume and low pressure.

At low RPM the bubble is strong enough to keep hot coolant from flowing into the heater core, but as the revs rise and the water pump increases speed (and therefore increases pressure in the system), the heated coolant forces its way past the bubble into the core, where the blower motor extracts its heat and flows it into the cabin. When revs fall, the system once again doesn't have the pressure to overcome the air bubble's blockage.

Bleed the core and you should be good.

 

Thanks again

 

I have an A4 B6 1.8t Quattro, have had cabin heat issues since I bought it, thought it was the heater core, had the dealer flush it when buying the car, helped the heat for a day or two, flushed it another two times with two other shops but to no avail. Replaced the heater core and still no heat.

Is there always supposed to be some level of coolant pressure in the heater core? Or is there a possible blockage with a valve that leads into the heater core? Could there be a temperature sensor that's malfunctioning and preventing flow to the heater core?

I don't have an over-heating issue as the gauge maintains 90.
The temperature gauge is not fluctuating, does this indicate the water pump is still creating enough pressure to push the coolant?

 

Bleed the core using the DIYs you can find. I had a clogged heater core which did the same though, heat went up a LITTLE when revved....there are some pics on this forum of my clogged heater core...it was BAD...what I mean by a LITTLE is, a few degrees and when I let off the gas, it would go away completely. If your heat is working correctly, your heat should be nice and warm/hot when blowing out.

When your car is warmed up, engine running, heat on, check both hoses to the heater core (be safe when doing this). When looking at the engine, heater core is sort of on center of firewall, by battery, 2 hoses going into the car (maybe under plastic cover). right hose is IN to the core, left is out. They should both be about the same temperature to the touch....if the left one is way cooler, the core may be blocked OR there's an air bubble in your heater core. Heater core is the highest point in the cooling system....you can also pull both hoses off (when engine is cool and off) and use a hose to run water through it and see the flow. But if your coolant is pink, looks good, I'm guessing it's just a bubble. There's also a DIY for the CLR heater core treatment.

 

Thanks for the feedback.

 

Thanks for the feedback. There was in fact an air bubble in the newly installed Heater Core. I bled the heater core by removing the return hose and routing it into my reservoir. With the engine on (cold) there was barely anything pumping through, I think this was when it pushed out any extra air...

Proceeded to attach hose and test....Success, consistent HOT air in the cabin, Just in time for winter

 

SPOT on. I was having the same problems (and symptoms - no heat at idle, significant heat with revs). I completely flushed the system because Mr. Lube did a **** poor job of flushing the coolant and I had a combo of green/pink in the reservoir. CLR treated the heater core but didn't get a lot of gunk out of it. Just air locked. Bled it through the pin hole in the output tube from the heater core.