mace wrote:
Marty already knows, but I guess I'm eating my hat re the Audi heater matrix mod. After changing the o rings a couple of times and the joint still weeping, I decided that, given the age of the matrix and the fact that it's probably full of junk even after trying to flush it both ways, I'd replace it, and went the Audi route.
It is possible to do this mod without cutting or otherwise modifying the HEVAC unit itself, by splitting it in half, and getting the new heater core in place through the entry point. The tight bit is the plastic divider that sits sandwiched between the two halves of the unit, but with it in pieces, you can get the end of the heater core past that.
The most difficult part of the job is properly sealing the edges of the heater core, especially around the hole in the edge of the HEVAC unit. The long edges of the hole are easy enough, but the short edges are extremely tight in comparison and it was difficult to get the neoprene in the gap without rolling itself up.
Anyhow now it's in, it's not going anywhere. I've put two hoses through the bulkhead ready for connection back to the coolant circuit.
There isn't a lot in it, and that adjustment to the heater box can be done in a couple of minutes with a sharp chisel, and not needing to split the box (though splitting it can be a good idea to check/free up flaps, regrease everything etc)...
I use some really thick foam now (as opposed to the thin stuff in the box) which gives a pretty good seal... I was put onto it by a member on another forum - and I'll link to it here for anyone else who wants some... it also does a pretty good job of stuffing the mammoth gap on the bottom of the rear face ducts!
Big Thick Foam!
Fingers crossed you don't get any drips now.. I used jubilee style clamps on mine and had to go back in once to nip them up - nowdays I use the Mikalor style constant tension screw clamps, which seem better again..
'06 4.2 Supercharged Black/Cream "Jess" -- Bought April 2021 (NZ)
'01 4.6 Vogue Black/Lightstone "Snog" -- Bought Jan 2012
'99 4.6 HSE Cobar Blue/Lightstone -- Sold March 2009
'95 4.6 HSE Epsom Green/Tan -- Traded June 2008