so back to the original thread, how you getting on re your list ?

Mine is steeped in oil and the wheel arch liner is missing?

I've got the wheelarch liners off mine until I do the Y-pipe, but I still couldn't get onto the bolt at the back. However, I might have done it a different way this time.

Original list.. urrm..

• Started demangling the radio wiring, but not finished. Got an aerial converter for when the head unit goes back in.
• Dash is out, and now that I've drained the coolant for the head gasket change, I can disconnect the heater matrix, get the whole unit out and get the flaps running smoothly. Will do the o-rings before it goes back in.
• All backlight bulbs sorted.
• LPG kit is here, but not done anything with it. Head gaskets first.
• Boot unlock button cleaned up and is less sticky.
• Cruise control probably still doesn't work, but I've fixed/checked most of it. It's just the last vacuum pipe that heads off towards the cabin that needs replacing now.
• Heated windscreen is definitely knackered. Open circuit on at least one half of it.

I'll probably make more progress on it once I get a suitable socket for the head bolts.

Hangs head.

Why not do the Audi matrix fit as you've got it that far down? For £30 in parts you'll never be troubled by O rings again!

mace wrote:

I can disconnect the heater matrix, get the whole unit out and get the flaps running smoothly. Will do the o-rings before it goes back in.

Orangebean wrote:

Why not do the Audi matrix fit as you've got it that far down? For £30 in parts you'll never be troubled by O rings again!

I'm still not sure what the attraction is with the Audi mod. The original O rings lasted about 15-18 years so most owners are unlikely to be troubled by them again anyway. The mod means the temperature sensor is on a rubber hose and not a metal pipe so won't report correct temperatures, the hoses are bulkier than the metal pipes, can perish and start to leak (most people will have had to replace at least some hoses before they've had to replace matrix O rings) and it requires bits to be carved out of the heater box and the matrix then secured in some way. If the original matrix is leaking or damaged by a gorilla doing up the clamp screw, then it'll need to be replaced but personally I'd still opt to replace for an original and retain the O rings.

It's personal choice, but mine needed work on the heater flaps, motors, the temp sensor had failed and the O-rings were leaking. If you've got to go in there anyway, you may as well replace the heater matrix which is cheap and will be as gummed up as the engine radiator which probably should have been replaced by now on most P38s.
So do you go with stock or the Audi one? For me, the Audi option eliminates a known weakness with a simpler solution with less joints and potential leaks. It's pretty much impossible to re-use the rubber firewall grommet but otherwise I don't see any real downsides - as long as you use top quality hose.

Additionally you could move the temp sensor to the steel pipe across the rockercover to eliminate the problem Richard pointed at.

Only if you have a Thor, on a GEMS, it's all rubber hoses.

That particular sensor only provides two inputs to the function of the HEVAC:

1. At cold startup if reported coolant temperature is low, the ECU delays blowers to avoid cold air being force circulated. As coolant temp rises the ECU progressively increases blower speed
2. When ignition switched on, if coolant cold ECU takes temp input from ambient sensor. If coolant hot it uses ambient temperature stored in memory.
   The only manifestation would be a delay of fans starting due to the insulation effect of the rubber hose. From my many sessions wandering around the cooling system with an IR thermometer, there's only a few degrees of temp difference between the rubber hose and the metal pipe it's connected to.

Don't get me wrong, I'm not saying I don't approve of the Audi mod, I just can't see the point. If you are going to the effort of taking the heater box out to change the matrix, why make extra work for yourself? As I understand it, the Audi core is fatter so bits of the box have to be cut out, then you've got to make up something to hold it in place before you run in the new hoses. When you can undo a couple of screws, pull out the old matrix, slot in a new one and the job is done. Put in some nice new O rings when it goes back in and the job is done and unlikely to need any more attention for the next 15-18 years. In that time you'd almost certainly need to replace the hose from the inlet manifold but you've made that job harder as you've now got to replace the whole run down to the heater.

I don't own a P38 but I've had hundreds in my charge.. I know for sure some have had problems with the matrix / O rings (told by owners), a very tiny minority have had the problem while in my charge. Hope not to be talking out of place, but given how long the original setup seems to last I'd go Gilbert's route as long as the seating areas for O rings seemed OK and I could be confident the problem wouldn't still exist or quickly return after going to the trouble of taking the dash out. If I wasn't confident with O ring seats I might go the Audi route. I wouldn't feel the need to redesign an aspect of a vehicle that generally lasts upwards of 10 years if it were any more work than just fitting standard parts lol.

Devils advocate here then; Gilbert is that a tacit suggestion that I should swap out the heater core for an oem replacement since I'm in there? :)

I'm a firm believer in if it ain't broke, don't fix it. But, it could be argued that even if it isn't showing signs of leaking it might do soon or it could be partially clogged and can only get worse. That would suggest that changing it would be good idea while you are in there. Whether you choose to do the modification and fit an Audi core or replace for an OE one is up to you but as I say, I don't think there are sufficient upsides to warrant the extra work. If it were mine, I'd leave it alone.

Heads off then.

What does it look like? Good, bad, indifferent?

Photo of the two heads off:

There is some damage on the edge of both the head and the block, around the point where it was blowing:

Another angle on the same damage:

I think this damage is someones botched attempt at sealing up the leaking head gasket with some kind of hardening metal putty.

I'm hoping it will chip off and won't require the heads to be skimmed, given it's really only on the edge of the head/block.
I've not yet checked the heads for trueness.

Looks like doing both heads was the right plan, too. The second head gasket is showing signs of degradation too, and I think between the two heads, probably 4 or 5 cylinders were either blowing or well on the way to thinking about it.

I guess if it's failed to atmosphere it's because the gasket's let go, rather than been cooked. I do wonder if it's maybe worth getting the heads skimmed anyway but I'm sure the folk who've had their engines well and truly apart will give you better advice :-)

Yeah there's a big gap in the gasket at that point. Haven't really done a lot of cleaning of the surfaces but as best I can see all the raised up bits on the head/block around that point are solely on the outer edge. If it were cooked, and I've not seen a cooked one so this is just an semi-educated guess, there would be damage all the way from the edge of the cylinder to the outside world.

Yeah, if it had been overheated badly enough it would be warped but if there had actually been much fire in that cylinder it might have burnt the metal a bit. Looks like it's okay though.

I wouldn't even consider putting them back without skimming them first. That way you know they are perfectly flat and smooth and you aren't going to be doing the same job again in 20,000 miles time. Skim, head stud conversion and the job is done for good.