Audi A4 B7 1.9 TDI Saloon

[PetruT]

Hello everyone,

I have a problem with my car and I can't solve it.

Last month I bought this car and I changed timing belt kit, waterpump, all the filters, brake discs and pads, etc.
Everything works perfect except heating.
Today I've been on a long trip (longer than usual) of 300 miles and when I arrived home I noticed that the coolant is very low so I had to top-up almost 3 litres.
There is no leak near engine, no leak at the exhaust, no smoke. Inside the car the mats are dry and everything under the mats. Now I checked the engine oil level and it is normal.

Engine temperature goes to 90 degrees but if I switch on the heating, it goes to 70-80 degrees. (No heating of course, just cold air).

I'm out of ideas so please help me if you know how can I fix it.

Thank you!

[Crasher]

When you turn on the heater blower you can see the temperature gauge drop but you are getting no heat? Has the coolant loss continued?

[PetruT]

When you turn on the heater blower you can see the temperature gauge drop but you are getting no heat? Has the coolant loss continued?

Thanks for your quick reply.

Yes. When I turn on the heater, the temperature drops from 90 degrees to 70 then very slowly to 80. In all the situations I have only cold air.

I'm still loosing coolant but I don't know where's the leak. I used one bottle of Wynns Stop Leak and one of Radweld Stop Leak but they didn't work for me.

Tonight or tomorrow I will try to reach the heater matrix maybe there's the problem.

[Crasher]

The temperature gauge should not react like that and if you only get cold air, where is the heat going? One thing you will have done is block the heater matrix with the silly bodge chemicals you have polluted the system with. You need to remove the thermostat (replace it anyway with a new genuine part) and back plus the complete system out and then run it with a powerful system cleaner and back flush again. When and ONLY when you are 100% sure the system is clean and free of nasty rad weld, you need to replace the heater matrix, which is not a terrible job on an 8E then you can refill the system with 50/50 G13/water, bleed it through and you should be back to correct function. It would be work reading the engine and HVAC systems for fault codes.

[PetruT]

The temperature gauge should not react like that and if you only get cold air, where is the heat going? One think you will have done is block the heater matrix with the silly bodge chemicals you have polluted the system with. You need to remove the thermostat (replace it anyway with a new genuine part) and back plus the complete system out and then run it with a powerful system cleaner and back flush again. When and ONLY when you are 100% sure the system is clean and free of nasty rad weld, you need to replace the heater matrix, which is not a terrible job on an 8E then you can refill the system with 50/50 G13/water, bleed it through and you should be back to correct function. It would be work reading the engine and HVAC systems for fault codes.

Hello again,

I flushed the system 4-5 times, I changed the expansion tank (was leaking at high temperature) and the matrix heater.
For the matrix core I used the old gaskets and clamps but I think I need a new set because it's leaking. The problem is that... I can't find them


Thank you again Crasher for your replies!

[Crasher]

They come as a kit of four parts from TPS or the Audi dealer spares department.