S3 heater woes

[ShEp1.8t]

Ok so this has been a bit of an issue for a while now.....

Heaters not blowing hot, apart from passenger side air vent as it gets luke warm.

Silica bag burst, caused no end of problems, had the header tank replaced, matrix replaced and everything flushed out and clean before fitting the new matrix. Heaters were all blowing lovely and hot.

Fast forward a year and a half and the heaters started blowing cold again, I thought it may be and airlock as the coolant level had been dropping and messing about. Turned out the water pump seal was leaking.

Booked into the garage, water pump renewed, radiator also renewed as it looked a bit poor. All vacuum filled and bled but still no heat from the heaters (apart from the passenger side vent)

So I've got the car back now and I've checked as much as I can, coolant control valve is hot either side, pipes going into the matrix are hot, pipes coming out are hot, everything seems to be doing. What it's supposed to be doing apart from blowing hot out the vents.


I've removed the glove box and checked the control flap motor, hard to tell of it was working or not, so I removed it and operated the flap by hand, but still just the passenger side getting warm, the drivers side refuses to get hot at all.

Kinda at my wits end with it, got a 2 month old baby so I kinda need the heaters working, but I've run out of things to check.

Any help would be much appreciated.

Had a look through various threads but I've not managed to find any info that I've not already checked

 

[J0N]

Have you tried changing the cabin filter? Cheap and easy so worth a shot….


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[ShEp1.8t]

Have you tried changing the cabin filter? Cheap and easy so worth a shot….


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Yeah changed that as it was filthy when I pulled it out, didn't look like it had ever been changed

 

[J0N]

I would’ve said the matrix is probably blocked again from the silica bag but it sounds like you have that covered? Strange one, this…..


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[ShEp1.8t]

I kind of hoped so, but im now at the stage I'm swaying towards just changing the matrix again.

It was previously flushed till it was clean and then replaced, I was hoping that was sufficient, but maybe there was some build up somewhere that slowly got through and blocked it again.

 

[J0N]

That’s what the symptoms are pointing towards. I had the same problem with my former S3 Saloon, it went in for the same issue as yours under warranty and never came home. Replaced the waterpump/thermostat and heater matrix but couldn’t get the coolant to run clear, they ended up buying it back.


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[J0N]

Was it a genuine, latest revision heater matrix? I was chatting to a local VW Specialist who mentioned an issue with casting sand. He also said that they change at least one a week and the A3 8V is probably the worst they do. Interestingly they charge £500 for the job with genuine parts where as Audi wanted £1675.


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[ShEp1.8t]

Genuine part used but that's over a year ago now. So unsure if it was the latest revision. I can do the matrix myself, fitting one isn't an issue, it only got done at the garage last time as it was under warranty

 

[J0N]

It looks a horrible job with the amount of interior trim that has to be removed and as you know, they’re notoriously difficult to bleed properly. Good luck with it mate, let us know if you solve the issue.


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[ShEp1.8t]

Half of it's out to check the motors anyway, I've got a vacuum bleeder for it, it does the hard work. Just want it to be right for selling it on for the next person. I know I'd be pi$$ed buying a car for a decent amount of wedge and it wasn't working.

 

[ShEp1.8t]

For anyone following, turns out it was the matrix again. Was only changed last year with a genuine part too, so I've bought one from the motorfactors, changed all the seals and o-rings, new clamps on each pipe too.

Whole system flushed clear again, as it was last time, for anyone doing one of these, do not buy from Audi, 1 it's expensive and 2 they have issues with casting sand, quite a lot of genuine part ones are failing again.

It's not a difficult job to do, just a lot of stripping bits off to get to it, of the side panel on the centre console was in 2 pieces it would be a 25min job.

I also didn't need to vacuum fill it or bleed it, just left it running for 5mins with the cap off. All good now

 

[J0N]

Glad you’ve got it sorted, did it look like casting sand?


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[ShEp1.8t]

Yep, 100% casting sand in it. Went for an aftermarket unit this time as Audi ones seem to have problems.