First post and I hope you can help as I am going mental with this[:@][:'(], here goes,

I have an A6 tdi 1998 110bhp with the engine code AFN.

A while ago I started to get a bit of coolant leak and eventualy found it to be from the header tank overflow. I replaced the tank cap and it seemed to make it a little worse, however the car never got above the normal 90c. The heater in the car also started playing up blowing cold when the car got up to the correct temp.

anyhoo, I have had the pump replaced TWICE as the first one started to leak straight away. The thermostat also wasdone when the pump was changed but I got another today and changed it as the garage had fitted a nonAudi part. What I have found is that the lower pipe to the radiator is cold when the top one is hot, one of the pipes to the cab/interior is cold when the other is hot.

I have BURPED! the system, I have placed a gardenhose in the top and bottomof the radiator and the water flows through fine. Why does it still appear to have a circulation problem and no cabin heat? help I love my car but want to kill it at the moment.

I want to take the thermostat out and check if it will circulate okay at that but will that damage the engine. By the way it is still ataying within the right temp range

 

did you BURP the system with the heat on HOT in the cab, look for the bleed nipple on the heating pipes going through the bulk head/ firewall

 

Did not know there was a vent nipple, can you confirm the position (picture)as I thought these were self venting systems with a bit of pipe massaging.

Cheers, John

 

only work on the petrol engine so no pictures sorry mate

 

You can pull out the thermostat (when cold) put it in a pan of hotwater and watch to see if it opens to test a thermostat. You could have a bad temp. switch or blocked heater core line.

 

Thanks for the replies, I dont think it is a temp sensor (correct me if wrong)because how would this effect the top and bottom radiator heat symptom. As for the heater core line is concerned,again I dont think so as I am getting heat when the dash temp is low then when the water temp raises the heat goes off.

I also noticed that on idle the car never gets hot and today the fan was on even when it said the water was cold.

HELP MEI AM GOING TOCRY!!!!!!!!!!!!!!

 

i'm assuming that your audi runs a blend air system and not a heater control valve?

 

Incorporation of auxiliary heater into coolant circuit[/align]Bleeding coolant circuit[/align]

‒Bleed engine coolant circuit in specified manner. [/ul]
=> Relevant Engine, Mechanics Workshop Manual; Repair group 19; Cooling
Note:
On vehicles with heater coolant shut-off valve -N279, briefly switch on auxiliary heater (approx. 1 min.; sufficient to actuate shut-off valve -N279 and circulation pump -V55) after filling with coolant and before starting engine. With ignition switched off, shut-off valve is actuated in auxiliary heating mode and vented via auxiliary heater circulation pump.

‒Once engine has reached operating temperature:

‒Switch on auxiliary heater (on vehicles with 6-cyl. petrol engine and 8-cyl. engine with heater coolant shut-off valve -N279). [/ul][/ul]
Notes:

â—†It is sufficient for the auxiliary heater circulation pump to run (auxiliary heater switches to "control interval" operating status on account of coolant temperature).
â—†On vehicles with 4-cyl. engine, 6-cyl. diesel engine and 8-cyl. engine with no heater coolant shut-off valve -N279 it is not necessary to switch on auxiliary heater for bleeding, as it is subject to constant through-flow. [/ul]

‒Top up coolant if necessary. [/ul]
just some other data that might help

 

Again thanks for the replies,

I have noticed the following after the second themostat change. The car takes ages to get upto operating temp with low blowerheat but heat all the same. When it is up to 90c norm then the heat drops off to cold unless I drive the car hard. The heat seems to mirror the driving manner ie hard = heat, normal = BALTIC. The other issue with driving hard is that it goes slightly above 90c untill the heat starts to kick out the blower.

I have tried my hardest to bleed the air from the system, however I think that when I do get it all out there may be a leak in the head gaskit putting it back in. There is no white smoke, oil in the water or water in the oil.

I am still loosing coolant through boil over...........