Suspect heater matrix is leaking

[ed_crouch]

Hi all,

I wonder if I might pick your brains...

Audi A4 1.9 TDi 110 avant, '97 model year, done about 185k (and very little wrong with it overall!).

Getting extremely misty inside and has been for some weeks, and when warm and the blower is switched on, cabin fills with coolanty steam and the screen mists up almost instantaneously. When blower is switched off, it all clears, as does the coolanty smell. It has also started using coolant.

Carpets arent noticeably wet...

So I'm assuming its a leaky matrix. Does anyone know of anything else it could be before I do battle with the dash?

Thankyou for your help.

Ed.

[crashcarter]

have you checked the plenum chamber

[ed_crouch]

As in heater plenum? Nope, have done nothing to the car yet. How would I do this?

Thanks,

Ed.

[crashcarter]

open the bonnet shine a torch in beside the battery look for any trapped water if so remove battery and pull out rubber grommet its only a guess

[Mockenrue]

How did you get on Ed? I have exactly the same symptoms as you i.e. steaming up and gradual coolant loss. Car is the same too (albeit a quattro saloon). Carpets and plenum chamber are absolutely bone dry.

[mrjolly]

you could tyr disconnecting the heater matrix. remove the two pipes to it ang join them together. you will lose your heater for the time being but if the steam stops . you know your matrix has gone.
regards sid.

[Mockenrue]

Thanks Sid, I'll give that serious consideration. What would you suggest I use to join them together with? Sorry but I'm not that skilled when it comes to under the bonnet stuff; changing bulbs and filters etc. is about my limit.

:beerchug:

[ed_crouch]

Yeh I removed and stripped the heater box. New matrix, wash and dry all of the heater box parts, reassemble and all is good. Old matrix was seeping and in any case, there will have to be a lot of coolant in the heaterbox before it spills out onto the carpets.

The job is a total GIT to do though on a B5 A4. A good 10 hours work, and without wishing to seem aloof, I'm a fairly experienced mechanic with a lot of patience. THis job should not be underestimated. You will have to drop the steering column (or remove the airbag and steering wheel and risk having to reset the airbag light), remove handbrake and centre consoles entirely, remove instrument cluster and remove entire dashboard, first removing pax airbag if you have one. Then you have to actually remove the heater box which requires some extremely intricate fiddling about.

I would advise anyone doing this job to remove the large structural support beam which passes over the top of the heate rbox and holds things like the fuse and relay panel on the drivers side. Yep, it looks like a right bugger to remove, but if you dont do this you'll find removing the heater box extremely difficult like I did.

Good luck. It can be done.

Ed.

[bobdabuilda]

Couldn't you just try and run some Kseal through the system in th ehope that it's only a small leak? Would save all the hassle of taking the dash off... and doing this.... helluva job http://www.audiworld.com/tech/int54.shtml

[Mockenrue]

I was considering the K-Seal option but after doing some research I found that many advise against it as it can knacker the water pump and potentially cause problems elsewhere in the cooling system. I guess it's really only a temporary measure anyhow.