C6 / C5 / 407 HDi V6 Engine Adaptive rear Torque Mount - How does it work?

[wurlycorner]

Hi all

Wondering if anyone knows how the 'Adaptive' rear "Torque Mount" for the HDi V6 (2.7 and 3.0) engines works?
This type of mount seems to be fitted across the 407, C5 and C6.

From researching the part, it has both an electrical and hose (I think vacuum?) connection - pics below.
Is this just a sensor that monitors the displacement of the mount under engine torque load? Or are they actuators that actively try to control it?
Does anyone have any knowledge of these and can explain or even better: any technical description/info/wiring/hose plumbing information - OE or otherwise???

I have had a search on here and quick look on C6 Owners (not a member there) but couldn't seem to find any more info - other than the fixings tightening torques here and instructions here - EDIT I've now joined C6 owners, downloaded that document and it does confirm there is a vacuum pipe and it's a solenoid valve not a sensor - so it is an actively controlled mount

Where this has started, is that my C5 3.0 HDi V6 has far too much driveline shunt (it's so bad I'm basically not driving it, because it will start to wreck things).
There's definitely something wrong with the engine mounts and from what I can see when trying to monitor engine movement on/off load, it's probably from the torque mounts (front and / or rear).
Looking at pics, both seem to be a similar design to the pics below - a rubber 'bush' that the gearbox bolts to at one end, linked by a rod to a 'damper' (not sure if rubber/fluid filled/air filled?).
The front doesn't have any electrical or hose connections (it's a 'passive' mount) while the rear does (it's an 'active' mount)?
What I'm not sure, is whether mine are failed/defective or (if the rear is meant to be actively 'controlled') whether the control side has failed?
I'd really like to understand how they're meant to work, so I can accurately diagnose what to do - do I need to replace, or is there a fault on the 'active' control side and I can sort that?

Thanks all

[wheeler]

Not sure if this is any good to you or what you already have?

[Stickyfinger]

Info, not PSA specific........

https://www.tomorrowstechnician.com/dia ... or-mounts/

The motor mount can be diagnosed with a handheld vacuum pump to see if it holds vacuum or not. If it leaks, it needs to be replaced. You can also use the vacuum pump gauge or your finger to see if vacuum is reaching the VSV control valve when the engine is idling. No vacuum or weak vacuum would tell you there’s a leak in the plumbing somewhere.

[wurlycorner]

Thanks gents, that’s great info - and no, I hadn’t seen either of those sources!
Looks like after I tackle the various suspension and steering joints tomorrow, that flipping ridiculous one-piece under tray is coming off, vacuum pump and digital scope meter are coming out to try and work out what is what…

[wurlycorner]

One further ask at this stage… does anyone have a wiring diagram that includes the control of/to that solenoid on that mount, please?
I’ve seen reference in some places to a separate ECU controlling it - which sounds excessive, but then again it could be argued even an active mount in the first place might be so???
And a schematic (or parts diagram) for the vacuum system that feeds it?
Thanks

[MGmike]

you'll find the vacuum system diagram/parts list here:

https://catalogs.ssg.asia/citroen/?lang ... I9PQ%3D%3D

[wurlycorner]

Only had a very brief look at this the other day (having to spend the rest of the time trying to sort out the other issues…).

Can confirm both front and rear engine mounts are active. They have different part numbers but look basically the same.

The solenoid valves are odd. I expect simple ‘in’ vacuum connection and out (to the item being controlled - in this case the mount) but no.
They have an ‘in’ on one side (coming from the airbox) and the other side has two ports.
One of these ports runs to the item being controlled (the bottom of the engine mounts in this instance) while the other runs out to the vacuum reservoir.

I don’t understand the theory of the operation there, tbh.

Disconnecting the hose from the port on the front solenoid valves confirmed the whole part of the system that includes the reservoir, was holding vacuum ok. My vacuum gauge didn’t have the right connector to attach, so I haven’t been able to measure it yet.

Unfortunately I didn’t have my scope meter charged so couldn’t use that, but I back probed the solenoid on the front mount (the rear mount is frustratingly inaccessible) and connected that to my normal voltmeter. Principle seems to be energised at low revs, de-energised at higher revs.

Wheeler - is there any more to that helpful document you posted? It seems to possibly be incomplete? The bottom of the page looks like it has a heading “Main Specifications” for a further section?

Thanks