Central locking, bodywork or electrics, pump running for 20 seconds!

[HPsauce]

The culprit!

BootLock.jpeg

When unlocking (which I can confirm is SUCK) this closes up somewhat so that generally works. The input pipe is fine.
When locking it just blows air out until the pump times out.
Incidentally using the valet lock just physically stops the rod moving which due to position somewhat restricts the leak but doesn't stop it.
The picture shows the UNLOCKED position, the rod is pulled in about 10mm when locked.

My thinking is that inside the unit will be a plunger which "should" have a sealing ring/washer of some sort so I guess that's also leaking.
It's not obvious how to get that unit out, or is just held by that one screw (in the picture) once the linkages are disconnected?

I wonder if a few dabs of suitable adhesive would be enough to seal that?

[HPsauce]

I wonder if a few dabs of suitable adhesive would be enough to seal that?

Well I tried my "go to" product and, for now at least, it seems to have worked after leaving to cure for about an hour.

For reference: KISS Powerflex Brush-on Nail Glue. As used by SWMBO.
It's effectively a cyanoacrylate superglue with I think some extra ingredients to make it less brittle when set.
Plus it comes in a handy bottle with a brush applicator, very useful for many repair jobs, I find it much better than tubes.

NailGlue.png

Incidentally the unit is held by two screws but getting it out looks to be a nightmare.
The long rod across between the boot latch and keylock (plus solenoid unit) all seem to be in the way and the fixings for that are under a thick black sound deadening patch. A job to be avoided if possible, plus the unit is over £100 at Prestige!

[HPsauce]

I've subsequently found an A8 Parts Forum thread from early 2020 when someone took a slightly different approach to this problem, though they did use gasket sealant as part of the solution.
See: https://forum.a8parts.co.uk/showthread.php?t=15457
Their instructions overlook the two screws in the boot lid interior handle and also seem to make light of removing the unit from its hiding place.

[MikkiJayne]

Oh, good find Its not that terrible to get out if you're used to it, but there's a sequence in which things have to come out and go back in. You can ship away the sound deadening over the two screw heads without too much trouble.

I think a flexible polyurethane would also work for this, or loctite 480 which is a rubber-reinforced cyanoacrylate.

[HPsauce]

I think a flexible polyurethane would also work for this, or loctite 480 which is a rubber-reinforced cyanoacrylate.

That's very useful to know, never heard of Loctite 480 before. If it starts leaking again I'll use that, cheaper than a £100 unit replacement (for just a gasket) which will be used and could fail soon anyway.
That seal plunges in and out so there's quite a lot of flexing, I don't necessarily expect my repair to last that long.
It's not used that often anyway and I might put the boot in Valet mode most of the time as that stops it flexing (but not being pumped).

Loctite 480 isn't cheap but AliExpress sell an equivalent for beer money (and I have other uses for it) so I might take that option now so I'm ready.

[HPsauce]

An observation on the actuator unit itself. It has identical air connections on opposite sides.
The "plunger/piston" is obviously in the middle and connected to the rod that has the failing seal/gasket around it.
The unconnected orifice obviously acts as a vent when the plunger moves.

BUT I suspect the design is such that it can be driven from either side, so maybe there's another model where the suck/blow (OR the lock) operates the other way round? The post on A8parts noted earlier does mention the C4 (100/A6) so I guess that had a similar system.

I also had a look at what other/earlier models do and the C3 is quite similar (but not plug and play) and has a "bellows" type of seal which would probably be more reliable. Part 443862153B.
It has a different linkage connection and isn't reversible so may work the "wrong way". Otherwise it might be a plausible option.

C3actuator.png

[MikkiJayne]

Is that new for £100? I probably have a bunch of these in a box in the workshop...

[HPsauce]

Is that new for £100? I probably have a bunch of these in a box in the workshop...

No that's the older C3 (and others) version, a lot cheaper, won't fit a D2! A8parts sell the D2/C4 for over £110 and I've not spotted any much cheaper that you'd want to buy! Just used it to illustrate the (probably) better bellows-type seal used then.

D2 version: https://www.ebay.co.uk/itm/198575742162

Incidentally I'm getting really confused about suck vs blow doing what. Everything I look at online (AND AI, but that's probably just picking up the same stuff) says SUCK to LOCK, BLOW to UNLOCK. But I'm sure my testing was the reverse; I could see, hear and feel air blowing out of the split when locking. Maybe I misinterpreted, does anyone know for sure?