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Thanks Richard, being the cautious type and having suffered from P38 faults being thrown all over the place I ‘jury rigged’ everything back on to test the HEVAC but wondered if I could get away with not connecting everything back up again -it was all a bit precarious without the dash in place! Passenger air bag isn’t a problem as it’s frame is still there.

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Alternative way to do it is with a pressure tester like > https://www.ebay.co.uk/itm/265189161289

Or make your own from a tyre valve and spare expansion tank cap if you prefer. Someone else on here did that without too much of an issue.

Advantage is you can leave the pressure on without the system getting hot at the same time. Doesn't need a lot of pressure there, I think the one I've got shows around 20psi to be in the test area and thats shown up leaks you wouldn't otherwise see (other than by dropping water level)

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Pressure test kit is a bit OTT for home DIY leaks - the drop in pressure tells you there is a leak but Mk1 eyeball is still required to determine where it is. I’ve never had much of a problem determining if coolant is leaking and where, and waiting for everything to cool down is not that much of chore - good excuse for an extended tea break! Besides which, the system needs refilling properly with engine running to ensure no air locks, some heat through the heater matrix is a good sign that there is coolant actually flowing through there and will test the O rings with heat as well as pressure.

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when i done my dash removal i taped up all the ducting so it wouldn't rattle or leak. don't forget to check the fans while you have access to them, also remove the evap without disconnecting it of cause, if you like and clean behind it , i didnt do this but there can be lots behind it.

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I wrapped a load of PVC tape around a lump of heater hose so it was a tight fit into the neck of the reservoir. Then wrapped a load more around one of my EAS emergency Schrader valves so it jammed into the other end of the heater hose. I managed about 25 psi before it blew out but by pressurising it to 20 psi allowed me to spot a leaking core plug on the Ascot.

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mad-as wrote:

when i done my dash removal i taped up all the ducting so it wouldn't rattle or leak. don't forget to check the fans while you have access to them, also remove the evap without disconnecting it of cause, if you like and clean behind it , i didnt do this but there can be lots behind it.

I have to replace all the foam seals on all the ducting as they have all disintegrated to powder/dust - the upside is that removing the residue is fairly easy as it all just rubs off! I also use carpet tape rather than duct tape when sealing the ducts - much stronger and more rigid as it has thread woven into it, and it’s black! Fans, distribution & blend motors already checked and working fine - I am wondering whether to change the latter motors anyway now I’m in there? After nearly 22 years I have to say that everything is surprisingly clean although I am giving it a good ‘going over’ as I don’t plan on doing this again anytime soon - my hands are too big for a lot of the jobs required to remove/replace the dash.

Work on hold at the moment as a) it’s freezing out there and I’m getting old; and b) I am in no rush and can take my time to do things thoroughly.

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O-rings are in. The infamous screw came out sweet as a nut. Old o-rings were decidedly hard and although they came out in one piece one of them just split when I gave it a light squeeze. However, the battery didn’t have enough oomph left after standing around for a couple of weeks or more and my earlier testing to turn the engine over and fire it up so testing delayed. Having put the instruments and air bag back in I didn’t get any faults up except for the usual windows/sun roof not set malarkey. Perhaps the pressure tester was not such a bad idea after all!

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Isn’t carpet tape 2 sided? I used Gorilla tape, also black and stronger and way longer lasting than regular duct tape.

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Garvin wrote:

Pressure test kit is a bit OTT for home DIY leaks - the drop in pressure tells you there is a leak but Mk1 eyeball is still required to determine where it is. I’ve never had much of a problem determining if coolant is leaking and where, and waiting for everything to cool down is not that much of chore - good excuse for an extended tea break! Besides which, the system needs refilling properly with engine running to ensure no air locks, some heat through the heater matrix is a good sign that there is coolant actually flowing through there and will test the O rings with heat as well as pressure.

If you can see the source of the leak then its not needed as you say. However if you have one of those pesky leaks that you can't quite locate (for example one that only leaks some of the time) the pressure helps not so much by the loss of pressure, but more by visible leakage that you can get hands around without having boiling coolant dripping onto them when your searching for the source. Most of the time its not needed I agree, but they are a useful tool. The set I brought was similar to the one linked, but was nowhere near as expensive as that one (and they all seem to be that sort of price upwards now).

I think someone on here (possibly Morat?) might have butchered an expansion tank cap and fitted a valve to it to do the same sort of thing.

I've found 20psi is usually more than enough to show up the stubborn to locate leaks, after all the cooling system shouldn't hold a great deal of pressure in any case (and removing the expansion tank cap obviously removes the pressure relief valve)

Duct tape does also vary greatly in quality, the cheap stuff from screwfix is fairly hopeless.

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The other problem with a slight leak is that it will only make itself known when the system is pressurised so only when hot. Then, if it is only a small leak, it will often evaporate before you can see where it is coming from so that is where a pressure test when cold really comes into its own.

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Harv wrote:

Isn’t carpet tape 2 sided? I used Gorilla tape, also black and stronger and way longer lasting than regular duct tape.

No, the carpet tape used is single sided used for carpet joins (from underneath obviously), double sided and it would stick the carpet to the underlay - the double sided stuff is used to stick carpet down round the edge when proper gripper is not used. It is very sticky, robust and hard wearing, indeed the downside is getting it off the ducting once it has been in place for some time! It is 10x better than duct tape. I haven’t used Gorilla Tape although I did notice black rolls of it in a shop t’other day - might give it a try when my carpet tape runs out.

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All back together now. No coolant leaks, dash to screen trim back in place and all heater flaps moving freely and well greased/lubricated. Blend and distribution motors all fine. Dash went back in OK with the only issues being:

  1. The upper duct on the drivers side - the sliding ‘collar’ just would not fit onto the centre duct. I even tried trial fitting just the collar on its own to see what the problem was. It just doesn’t fit over the central duct. I tried heating it and making it very pliable but it just wouldn’t go on. I can only think that the plastic has shrunk over time - it is exceedingly loose inside the duct it slides in - well it was until the additional foam seal made it snug. It is now about 80% fitted to the central duct and supplemented with lots of tape! Indeed all the ducting joints are now supplemented by plenty of tape!

  2. I had to fabricate a replacement central gasket twixt the dash top and the ducting below. Foam sheet cut to shape and then covered in duct tape top and bottom to give it strength. Gasket fixed to the central ducting with double sided tape. Jobs a good ‘un.

  3. When refitting the glove box release cable I did not locate the release ‘claw’ properly into the lid. I shut the glove box and the ‘claw’ dislocated and I was left with a glove box that wouldn’t open. It’s worse than that because at that point I realised what I had done because, well, I made the same mistake a few years ago when I replaced the damper - doh! At least I knew how to rectify the situation!