Hey all -

New to the forum, and a relatively new Audi owner. We have a 2004 A6, 2.7t and we're very impressed with the car!

I'm running down a problem with a lack of heat at idle. The cooling system is a bit of a mystery to me and this is making diagnosis difficult. I don't find a traditional radiator cap and I gather that there is none. Is the coolant reservoir cap effectively the same thing on this car? If it is, the cooling system reservoir must be within the pressurized part of the system - is this correct?

Ordinarily I'd run the car with the radiator cap off to purge any other air from the system but the lack of a traditional radiator cap leaves me to wonder if and how this is otherwise done.

I've bled the allen-head fitting near the top/front of the engine (sorry, don't remember what it's called) and I've also vented the upper heater core hose. This offers improvement but after a week's time I find the problem returns and gets a little worse with each day until I bleed these again. I don't find that the car is using coolant other than that which I'm losing when I vent the system.

Is there another bleed location and / or method?

What else am I missing?

Thanks in advance.

Terry

 

Greetings yes you are correct we don't have a traditional radiator cap because we have what is called a "sealed system". Coolant is added through the expansion tank that is located on the driver side so essentially yes this would be our "radiator cap". Usually no heat is an indicator of a failing water pump so hopefully that is not the case because it is a pretty involved job (timing belt removal). Have you had any overheating issues along with that?

 

No overheating issues and no apparent indication of contamination of the coolant or bubbling into the overflow tank, such that you might see if you lost a head gasket. I re-bled last night and if the problem returns I think I'll flush the heater core and re-bleed just to rule an obstruction there out.

Other ideas?

 

its not a failing water pump, basically the design of the those coolant systems is horrible. I am having the exact same issue with my A4. I know a different car with a different engine but the system is the same, overly engineered and designed to fail. About 85% of it is made out of plastic and the original "pink" coolant simply eats it away. If i remember correctly your engine does have and external or so called auxiliary water pump which helps push coolant to the heater core. so you can have heat. Most if not all water pumps on the Audi's are way to small to push enough pressure in the overly complicated and unnecessary spaghetti soup called a coolant system. If I were you I would check with a vag-com to see if your auxiliary pump is working. I personally spend almost 3 hours last night bleeding my heater core to get a little bit of heat at about 2000 rpms and almost none at idle. I already replaced my heater core which is the only easy job on the B6, but bleeding this system and having hot heat is almost next to impossible... I am pretty sure you just like myself made a huge mess of coolant all over the place thanks to the "superior engineering" of the bleeding hole on the heater core hose... and after spending 3 hours in my garage last night on my drive back home i lost all heat again. This morning I simply took my Toyota to work and got really warm in it. I am planning on adding an auxiliary pump on my A4 just to help flow coolant a little bit better into the heater core and hopefully have heat during the winter. Those cooling systems are notorious for creating air pockets and bleeding them is nothing else but a nightmere. I have already bled my system 3 different times with the exact same results as you... I know many people will get offended with me but the words reliability, ease of operation, simplicity and "it simply works" cannot be used in the same sentence when it comes to audi cooling systems

 

If the issue were the water pump I'm not sure I'd find improvement after bleeding the system so I'm inclined to doubt this as the cause. I don't yet know enough about Audi to make an educated guess let alone a diagnosis of the problem. I'll look into the auxiliary water pump idea.

I bought a cheap-o Audi repair manual on ebay, confirming the old adage that you get what you pay for. First things first - must buy a good manual before I go much further.