P38A Heater matrix o-ring / pipes - advice needed !

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AndyF07

Active Member
Posts
109
Location
UK
So today I decided to replace the o-rings on the heater matrix as footwell damp. Used the 'quick' method of cutting hole for access and all went well. Old o-rings didn't look too bad to my surprise and I couldn't see obvious evidence of a leak but changed them over to the new ones.

When I started the engine to check there was a definite leak with the coolant dripping about an inch away from the seal from the upper matrix pipe, which increased when revs increased. After checking my work over and over the same issue remained.

After a while I suspected perhaps the leak wasn't from the o-rings but from the pipes. Wrapping some cloth around the pipe a couple of inches away from the drip (i.e towards the fire wall) stopped the leak and the moment I released it the leak returned. So I am now thinking there is a leak from the back of the pipe.

Could anyone help me on how to get the heater matrix pipes out to check / replace them please. I can't see a way to undo the retaining bracket on them so do they need to come out under the dashboard? If so is it possible without removing the dashboard fully rather than the 'cheat' I have done?

Lastly in an emergency and I need her on the road is there any issue with bypassing the heater matrix totally?

Any advice greatly appreciated guys.
 
AndyF07 said:
So today I decided to replace the o-rings on the heater matrix as footwell damp. Used the 'quick' method of cutting hole for access and all went well. Old o-rings didn't look too bad to my surprise and I couldn't see obvious evidence of a leak but changed them over to the new ones.

When I started the engine to check there was a definite leak with the coolant dripping about an inch away from the seal from the upper matrix pipe, which increased when revs increased. After checking my work over and over the same issue remained.

After a while I suspected perhaps the leak wasn't from the o-rings but from the pipes. Wrapping some cloth around the pipe a couple of inches away from the drip (i.e towards the fire wall) stopped the leak and the moment I released it the leak returned. So I am now thinking there is a leak from the back of the pipe.

Could anyone help me on how to get the heater matrix pipes out to check / replace them please. I can't see a way to undo the retaining bracket on them so do they need to come out under the dashboard? If so is it possible without removing the dashboard fully rather than the 'cheat' I have done?

Lastly in an emergency and I need her on the road is there any issue with bypassing the heater matrix totally?

Any advice greatly appreciated guys.
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No problem looping the heater pipes under the bonnet.
 
Rubberknees said:
As Data says just fit a U bend into the hoses where they enter and exit curtain wall. I did this whilst changing heater matrix for Audi one which does away with metal pipes and O rings.
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@Rubberknees Thanks that's good to know. When you changed the heater matrix did you change the feeder & return pipes too? Do they just pull through from under the dashboard and then thread the new ones back through to the engine bay ? Cheers
 
The Audi matrix uses rubber hoses from the matrix all the way in to the engine bay so the original pipe are just removed.
when i changed my original pipes because i had to cut them out the new ones were pushed back in from under the dash its a fiddle but can be done, and replace the o ring clamp screw with a stainless alen head bolt with a bit of copper grease on it.
 
The two ally pipes that go through the firewall can be pulled out but as far as I remember it was quite fiddly with the dash out because of the bends in the pipes and all the other air ducts, cables and so forth in the way. You might get them out but I doubt you would get them back in. Feeding the pipes back through the grommets into the engine bay is a PITA because the grommets tend to pop out.

I'm intrigued as to where it is leaking from. The ally pipes connect to the matrix where thise o-rings are. Of course, they must be on straight or it won't seal properly. The pipes then come out in the engine bay the other side of the firewall where the coolant rubber hoses connect but there are grommets to stop anything getting through the firewall.
 
Grrrrrr said:
The two ally pipes that go through the firewall can be pulled out but as far as I remember it was quite fiddly with the dash out because of the bends in the pipes and all the other air ducts, cables and so forth in the way. You might get them out but I doubt you would get them back in. Feeding the pipes back through the grommets into the engine bay is a PITA because the grommets tend to pop out.

I'm intrigued as to where it is leaking from. The ally pipes connect to the matrix where thise o-rings are. Of course, they must be on straight or it won't seal properly. The pipes then come out in the engine bay the other side of the firewall where the coolant rubber hoses connect but there are grommets to stop anything getting through the firewall.
Click to expand...

@Grrrrrr Thanks. So do you mean once they're out you don't think there's anyway of getting them back? Or just without removing the dash fully?

I must admit I was surprised myself and not what I expected to find. Also can't seem to find a single other example online or on forums.

I can't find anything in the engine bay suggesting a leak running down somehow but will check with a fine tooth comb later if the rain here ever stops. It seems like the coolant must either be leaking on the back of the upper ally pipe or running down the back from elsewhere. I intend to get a camera up there and see if I can see more. But it definitely stops the leak by wrapping a cloth around it (above where the coolant drips from) when the pipes are all connected and system has some pressure. Which logically suggests the o-rings seals are fine. Also as the coolant heated up there was a bit of 'steam' from behind the same area of pipe which I wondered maybe the coolant escaping under pressure from the pipe?

Any other ideas would be massively appreciated as I am a bit reluctant to remove them as it is a pita only to find they're ok?
 
AndyF07 said:
@Grrrrrr Thanks. So do you mean once they're out you don't think there's anyway of getting them back? Or just without removing the dash fully?

I must admit I was surprised myself and not what I expected to find. Also can't seem to find a single other example online or on forums.

I can't find anything in the engine bay suggesting a leak running down somehow but will check with a fine tooth comb later if the rain here ever stops. It seems like the coolant must either be leaking on the back of the upper ally pipe or running down the back from elsewhere. I intend to get a camera up there and see if I can see more. But it definitely stops the leak by wrapping a cloth around it (above where the coolant drips from) when the pipes are all connected and system has some pressure. Which logically suggests the o-rings seals are fine. Also as the coolant heated up there was a bit of 'steam' from behind the same area of pipe which I wondered maybe the coolant escaping under pressure from the pipe?

Any other ideas would be massively appreciated as I am a bit reluctant to remove them as it is a pita only to find they're ok?
Click to expand...

I doubt you'll get them out without removing the dash but I may be proved wrong. If they come out they'll go back!

If the water is coming down the pipes and definitely isn't from the o-ring join then maybe the grommets through the bulkhead are gone and the ally pipe has worn through on the steel - although that wouldn't stop when you wriggle the pipes. The only other thing it can be is the join with the rubber pipes but I cannot see drips getting through the bulkhead. The matrix has been known to leak but obviously that's the other direction.

You're sure it is coming down from the bulkhead? And it is coolant not rain water? I could see the windscreen trim leaking and dripping down through there somewhere.
 
Grrrrrr said:
I doubt you'll get them out without removing the dash but I may be proved wrong. If they come out they'll go back!

If the water is coming down the pipes and definitely isn't from the o-ring join then maybe the grommets through the bulkhead are gone and the ally pipe has worn through on the steel - although that wouldn't stop when you wriggle the pipes. The only other thing it can be is the join with the rubber pipes but I cannot see drips getting through the bulkhead. The matrix has been known to leak but obviously that's the other direction.

You're sure it is coming down from the bulkhead? And it is coolant not rain water? I could see the windscreen trim leaking and dripping down through there somewhere.
Click to expand...

Definitely coolant as blue. I am pretty sure somehow there is a pin hole in the back of the ally pipe but will triple check everything as was trying to avoid removing the dash. I'll get a little camera to pop up there and see if it sheds any light. Would also explain why the footwell was damp but no obvious evidence of leaking at the o-rings. Thanks for the advice and I will report back!!
 
I pulled the metal piping out from under the dash with out a lot of fuss but as I was getting rid of them wasn't too careful with them. As replacing with the hoses I took the curtain wall grommet out threaded hoses through it then worked hoses down to new matrix and then popped grommet back into curtain wall. Maybe I was lucky but the job was easy enough. I used the NISSENS 70220 HEAT EXCHANGER INTERIOR HEATING and it slotted straight in
 
As said i had to replace the pipes on mine and managed to get them out and the replacement ones back in, all done with out taking the dash out, it was a long time ago so cant remember which bits of trim were removed but it is possible.
 
I would first try removing the glove box assembly. I think that will allow the pipes to come out. Fiddly to refit but I think you would have to remove it anyways if the dash had to come out. Be carefull removing the release cable so that you do not break the plastic latch assembly. There are 2 small catches that you need to carefully depress to remove the latch assembly. The cable comes with it.
 
Gord Wedman said:
I would first try removing the glove box assembly. I think that will allow the pipes to come out. Fiddly to refit but I think you would have to remove it anyways if the dash had to come out. Be carefull removing the release cable so that you do not break the plastic latch assembly. There are 2 small catches that you need to carefully depress to remove the latch assembly. The cable comes with it.
Click to expand...

Its behind the instruments and steering on right hookers over here, yours must be easy:)
 
Gord Wedman said:
I would first try removing the glove box assembly. I think that will allow the pipes to come out. Fiddly to refit but I think you would have to remove it anyways if the dash had to come out. Be carefull removing the release cable so that you do not break the plastic latch assembly. There are 2 small catches that you need to carefully depress to remove the latch assembly. The cable comes with it.
Click to expand...
That's LHD only
 
AndyF07 said:
Definitely coolant as blue. I am pretty sure somehow there is a pin hole in the back of the ally pipe but will triple check everything as was trying to avoid removing the dash. I'll get a little camera to pop up there and see if it sheds any light. Would also explain why the footwell was damp but no obvious evidence of leaking at the o-rings. Thanks for the advice and I will report back!!
Click to expand...

You might, possibly, get away with something like Quiksteel if you can find the pinhole. That would save a lot of hassle.
 
Gord Wedman said:
I would first try removing the glove box assembly. I think that will allow the pipes to come out. Fiddly to refit but I think you would have to remove it anyways if the dash had to come out. Be carefull removing the release cable so that you do not break the plastic latch assembly. There are 2 small catches that you need to carefully depress to remove the latch assembly. The cable comes with it.
Click to expand...

I definitely wish I had a LHD just now lol :)
 
Grrrrrr said:
You might, possibly, get away with something like Quiksteel if you can find the pinhole. That would save a lot of hassle.
Click to expand...

I've found the hole now on the back of the pipe and it feels pretty tiny. In fact it hardly leaks at all once the coolant is up to temperature ! I came to the same conclusion and have ordered some JB Waterweld which has got good reviews. Fingers crossed it does the trick as the pipes are really wedged in there:eek: The irony is the actual o-ring job was a lot simpler and quicker than I expected ......
 
Last edited:
AndyF07 said:
I've found the hole now on the back of the pipe and it feels pretty tiny. In fact it hardly leaks at all once the coolant is up to temperature ! I came to the same conclusion and have ordered some JB Waterweld which has got good reviews. Fingers crossed it does the trick as the pipes are really wedged in there:eek: The irony is the actual o-ring job was a lot simpler and quicker than I expected ......
Click to expand...

Can you see how the hole was made? Is it rubbing against something?
 
Grrrrrr said:
Can you see how the hole was made? Is it rubbing against something?
Click to expand...

No it’s totally clear and nothing at all that would cause it. The o/rings have been done before at some point as the hole was already cut in the panel. Maybe it got damaged then somehow.
 
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