2.2 HDi torque reaction mount

[jml]

I was gong to start this post asking if mine was too soft, but then I thought better of it !

I’ve been trying to pin down an intermittent and slightly unusual vibration/shudder in my C8 2.2HDi 173. When underneath the car I noticed that it is quite (too?) easy to rock the engine with a small prybar in the lower torque reaction mount. I have a video showing the play however, unfortunately, it appears too large to post on here.

Looking at the upper engine mounts and the upper torque reaction mount there doesn’t seem to be excessive movement however I reckon the lower one is quite a long way from the axis of the main mounts and so, maybe, quite a bit of movement here is not abnormal ?

This mounting was replaced once before, about 25,000 miles ago. The car has now done 161,000.

I temporarily fitted a small bolt to minimize the movement and, on a short test drive, I’m pretty sure it reduced, but not totally stopped, the vibraton. My suspicion therefore is that the fundamental cause is something else but exacerbated by wear in this mount.

So I wonder if anyone can help me with any of the following questions:

• What is the part number of this mounting (which is pressed into the bracket that retains the right hand intermediate drive shaft bearing) . Is it 180941 ?
• I am surprised that the engine undertray has a very specific plastic trunking built into it to direct cooling air straight onto this mounting – presumably Citroen wouldn’t have gone to all that trouble unless it needed cooling ? Do other models feature this ?
• Is the same system used on the C5 and C6 with the same 2.2 HDi twin turbo ?
• As this is supposed to, presumably, minimize the torque movement of the engine, should the solid parts be at the front/back of the mounting, rather than at the top/bottom ? I have however seen another and that too has the solid elements at the top/bottom.
• I will change this mounting but, even though the other mounts don’t appear to show excessive play, should I consider replacing those as well?

Any thoughts or advice would be very welcome. Thanks in advance

[GiveMeABreak]

Hi Julian

As far as the part 180941 is concerned, it's called the engine flexible bush, part (15). It is currently still available and costs £60.14 inclusive.

Anti Torque Links are (3) & (6)
Engine Mounting Bracket (8), 12), (14) & (23)
Engine Elastic Mounting Brackets (10) & (11)
Engine Flexible Bush (15)

[jml]

Hi Marc

Thanks for that.

With your immense knowledge, have you got any thoughts about my other questions - like was the same arrangement on other Citroens with the same engine ?

Cheers

Julian

[GiveMeABreak]

Hi Julian - I'm not quite understanding what you are referring to. If it's the under tray engine protection for your C8 as follows and that is a single part:

Most have this protection, but I can't see any other obvious air channels or deflectors. The covers are completely different for other models too.

The only reason for the depression on the one side of the engine protection I can see is to allow for the shape of the flexible bush as it's only on that one side.

[jml]

I can quite understand why you can’t understand from that picture ! Mine looks quite a bit different from that.

I’ll try to post a picture tomorrow but on mine there is rigid rectangular plastic tube that ducts air from the left hand front of the car across under the engine and ends up in a slightly smaller diameter almost ‘jet‘ directed right at that mounting.

It is definitely a factory fitment - I’ve known the car from brand new and it’s an ex-Citroen UK press car - probably the first in the country.

I just wonder if they did this because they knew it needed to be kept cool to prevent it softening ??

[white exec]

Re the lower torque mount, some engines were designed to have some free fore-aft movement, limited by that lower mount, which has free space built into it. The engine is supported and pivots on its upper mounts. This way, vibration transfer to the bodywork is minimised. If you want to experiment, you can just push a short length of rubber hose into the side gaps of that lower mount.

[jml]

Thanks Chris,

That’s very useful as it explains the orientation of the mounting. As fitted the mounting had solid rubber parts at the top and bottom and voids to the front and rear of the mount. The torque reaction of the engine on this mounting is forwards/backwards and so acts on the voids ie It doesn’t resist the reaction very much.

I was wondering, when the dealer replaced it 25,000 miles ago, whether they might have refitted it 90 degrees out, but from what you say it sounds like it was correct.

As you say, it pivots on the upper mounts but, because this lower mount is quite a distance from them, there can be quite a bit of movement there - and it’s quite easy to ‘pivot’ the engine with relatively little leverage at this mount. The question I have to answer is whether the hard elements of the mount have softened excessively, making it TOO easy to pivot, thus exacerbating my vibration ?

Cheers

Julian

[jml]

Here are some pics of the undertray. Ignore the silvery pads, that’s what I fitted about 100,000 miles ago to replace the original flimsy felt like sound insulation that was disintegrating !

So has anybody seen anything similar on a C5 or C6 with the 2.2 173 HP ?

[jml]

Finally, this is a pic of where that air comes from.

I’ve just realised that that goes up behind one of the main fans which, of course, are on all/most ? of the time the air con is on so it blasts air at that mounting

[GiveMeABreak]

Ok, I've got it now with those new pictures.

Basically it's an air deflector that's located on the engine cooling system. Part 11 is connected to the front cooling fan housing and then goes into that flat tube that is shown greyed out. I have not had any luck identifying the part number for it - so can only assume it is incorporated into the under engine protection cover, despite it not being show on that diagram (to avoid any confusion perhaps).

[jml]

Thanks again Marc and yes, it’s plastic welded into the undertray.

You know how powerful those fans are and I’m wondering whether, because I quite often have the air con turned off (but use it at least once a month) I’ve just not been allowing enough air through to cool that mount ?

Still be interested to know if C5 / C6 use similar and, if not, why on earth would it be just on C8 ?

[GiveMeABreak]

I've just confirmed that item (11) is not found on any other vehicle - apart from the Peugeot 807 with the same engine as these are essentially the same vehicles.

[jml]

Thanks Marc

Bit strange that they felt it necessary, for some reason, to do it just on C8/807

[GiveMeABreak]

The only thing I can think of it that as it is specific to this engine, but ONLY as fitted on the C8 and 807, then it must be to do with the mounting position / angle / space / location on these vehicles that makes it a requirement.

The same engine on the X7 with similar twin cooling fans does not have this part - but the X7 generally has oodles of room under the bonnet.

I would suggest that this may be supported by the fact that the engine mountings are completely different too.

[white exec]

XM 2.5TD also has an air-cooled engine mounting, just out of interest.

The engine is designed to pivot through a few degrees around its horizontal axis, and is supported there by a silentbloc engine mount at each end. Rotation is limited by a torque rod and a couple of 'buffers', one of which (the lower one) is pretty much identical to yours.

The RH engine support/pivot (silentbloc rubber) receives some cooling air via a 25mm pipe, which also cools air in the plastic ECU housing.
This RH pivot is slap bang in the middle of the belts area (3 belts, under a cover) and presumably would run uncomfortably hot without some additional airflow.