W210 boot vacuum problem

[W210 E55]

I've got an issue with my folding headrests and the boot locking/remote opening.

I think they are probably all related, the headrests do not drop down but I can hear the pump going, the boot does not open with remote or dash button nor lock/unlock with central locking so I need to use the key to turn & push.

I have stripped the back end down looking for leaks but cannot find any. But have discovered that it seems to be a problem of pressure not releasing. When I disconnect the rear pipe from the pump it releases pressure, I can reconnect it and the boot will remotely open but not close until I disconnect the pipe again. Next to the back seat where the pipes go into the boot is a junction where it splits off for the headrests which has some kind of valve and also a plug to blank off one connection which does have a small pin hole through it. I've tried changing this around in various combinations but no change.

Question is, is this some kind of valve which is stopping the pressure releasing and needs replacing or am I way off and if so any ideas?

 

[Dieselman]

There shouldn't be a valve, just a T connector.
Unplug the tube from the pump, blowing will perform one operation, sucking the other.

 

[W210 E55]

I'll take a photo later but I'm sure it had an arrow on it indicating it's directional, it's definitely more than just a T piece

 

[W210 E55]

This is the part, what is it? It looks like more than a T piece. The orange bung does have a small hole that looks like it should be there

 

[W210 E55]

Update after tinkering today, and looking at the pipes on another 210 I removed the bit I described as a valve and just connected the white headrest pipe with a T piece, and hey presto the boot works. Still no headrest drop but I can remove those manually if needed so happy with that for now.