I have an Audi A3 2.0tdi 2014 that has a very frustrating problem.

The car is leaking coolant when on a run, the coolant is coming from the expansion cap and seems to be caused by back pressure building up in the coolant system. The temperature gauge does not move above the normal running temperature though and I have had no problems with overheating

I have also noticed that the cabin heater blowers are not as hot as they used to be and that the passenger side is cooler than the drivers side.

The car has had the expansion bottle and cap changed, the heater matrix pipes are both hot and the garage checked for combustion gasses in the coolant but could not find anything, so hopefully the head gasket is ok? 

Has anyone had this issue and managed to find out the cause please, as I am rapidly getting very frustrated that no one can locate the problem? 

Hello Andrew from the Homeland.

My first port of call would have been the coolant cap, but…

Have you had the coolant operating pressure monitored? 
Kind regards,

Gareth. 

AIR LOCK  TO 

13 hours ago, audia4b5kev said:

AIR LOCK  TO 

I’ve been told by the garage they’ve checked for an airlock and there isn’t one. 

13 hours ago, Magnet said:

Hello Andrew from the Homeland.

My first port of call would have been the coolant cap, but…

Have you had the coolant operating pressure monitored? 
Kind regards,

Gareth. 

HI Gareth

Yhe car was put in for a pressure test, but they could make a decent seal to get this done. I changed the expansion bottle and cap with Audi parts and the problem is still there. 
On another forum, a few people are saying heater matrix could be the problem?

Im trying to book it in with an Independent Audi specialist  , would you have any recommendations? I’ve been speaking to R Tek in Swansea.  

 

Hello Andrew, 

When you say there was an abortive attempt to pressure test the system, was that with the old reservoir and cap? If so, have you had a repeat test with the new parts? If not, I would certainly arrange that - with another garage. 
Heater matrix problem? - why should that be over pressuring the system? Simple test:- turn the heater off and see what happens. 
Sorry, I don’t have any experience of an Audi independent in S. Wales. 
Kind regards,

Gareth. 

4 minutes ago, Magnet said:

Hello Andrew, 

When you say there was an abortive attempt to pressure test the system, was that with the old reservoir and cap? If so, have you had a repeat test with the new parts? If not, I would certainly arrange that - with another garage. 
Heater matrix problem? - why should that be over pressuring the system? Simple test:- turn the heater off and see what happens. 
Sorry, I don’t have any experience of an Audi independent in S. Wales. 
Kind regards,

Gareth. 

I don’t think the garage carried out a pressure test after the new cap and bottle were fitted.

The heater matrix can get blocked which reduces flow around the system and this produces back pressure which can cause coolant to leak out of the expansion bottle cap apparently. 

Thanks Andrew,

So it looks like you’ve never had a reliable pressure test done on the system. This would be an obvious next move in my book. 

Sorry, I cannot follow your logic re. possibility of the heater matrix causing your system to pressurise. By your logic, every Audi would over pressurise when the heater is turned off! 
Also, in your case, you say inlet and outlet heater pipes are both hot, so the matrix cannot be clogged. 
Sounds like you first need to get the system pressure tested, if you are going to avoid unnecessary expense, but as with any advice on here, the person seeking advice is free to do what they want to do. 

Kind regards,

Gareth. 

Hello Andrew,

Can see you’ve revisited the form - any further updates on the advice already given?

Kind regards,

Gareth.m