whatever you do dont put Radiator Weld/Sealer into your car. it'll cause more damage than it'll fix!!
I agree, it broke my heater matrix so I had to replace itat the weekend! Arse of a job:
1. Undo 2x nuts from the bulkhead, theye are located under the 2 water pipes that pass through the bulkhead, vertically inline with each other. If you are unlucky like me these will just spin, don't worry if they do, just means you have to get medieval later on
2. Remove the matrix inlet & outloet pipes, they will likely bee those horrible clips VW like to use, get some big pliers on them and be patient.
Now inside the car:
3. Remove both dash undertrays (several screws) gearknob & gaitor, and then the centre console (1 screw under gearlever gaitor)
4. On the drivers side, undo 3 screws on the plastic trim piece, it should then come away complete with its foam backing.
5. Remove both centre vents, they just pull out. Then undo the 2 screws holding the centre vent surround in place.
6. Heres a tricky bit, the centre vents are held on to the housing by staples, you'll just be able to see them looking down the holes. Remove the staples then you'll be able to unclip and remove the centre vent housing. I used a long sharp knife to gently prise the staples open, patience is a virtue
7. You'll now be able to remove the front half of the heater box, it is held in place by 2 plastic nuts. Wiggle the unit whilst you reach up under the dash to disengage the connections to the passenger vent, it will come out with a little persuasion.
8. Next remove the lower part of the heater box, its a bit tight against the tunnel, but a bit of wiggling and it should come off.
9. Now you'll see the 3 heaterbox control cables, 2 at the front and one on the drivers side. Undo the metal clips and remove the cables from the control levers. If you have trouble doing this then see step 10, otherwise skip step 10
10. If you have trouble with the control cables, remove the heater sliders and fan control switch with a good pull, then unclip the heater facia carefully, then remove the lighting plug and fan control switch (if you pursh it upwards the whole unit comes away from the fascia). Then remove the 3 screws and the whole heater slider box will come out from under the dash giving you enough slack to remove the control box without disconnecting the control cables.
11. Another tricky bit, you need to unclip the heaterbox from the fan intake on the passenger side, it is held on with 6 clips on the front, back top & bottom and is a bit of a fiddle. I found verbal abuse helped me here, and also releaved a bit of stress at the same time
12. Now you should be all set to remove the heaterbox and matrix! If you couldn't get the 2 bolts off in step 1 you'll have to pull hard to disengage the heaterbox from the studs, once you do after more verbal abuse and faffing the heater box will come out!
be prepared for coolant spillage though, unless you manage to keep the unit upright when removing it (yeah right!)13. The matrix is held in with 2 clips, undo these and the unit wiull slide upwards and out. Swap in the nuw unit and transfer the foam gasket from the old unit (very important, otherwise you'll get engine bay fumes in the cabin!)
14. Reinstallation is the reverse of removal, if the old studs are still in the bulkhead you might have trouble getting it back in, in the end I had to remove the lower stud completely and heel around till I got it back onto the top stud. You can still buy these from VW, which was handy as the lower stud sheared off when I did mine.
15. Enjoy a lovely warm car! It will smell funny for a while, I even got white smoke coming out the vents when the matrix got really hot, but this stopped after a couple of days.
