General: Vibration, Idle & While driving (2006 185bhp D5)

[familyman2]

Hi need I bit of help with this if you can.

Ok bit of a back story. I have had Vibration only slightly whilst driving and then when i got to 80 mph (continental driving) the vibration was through the steering and the through the throttle pedal and was bad.
Recently I got the car serviced and thought while the car was up in the air will have a look at the rear mount and to be fair looks like new no wear or anything, must of been done from previous owner. I have replaced the top mount and the front is not new but seems ok. While I was down under the XC90 I noticed that the lower mount was Shot! so I bought and upgraded a Poly lower mount thinking this must be the problem, and I was mistaken now the car vibrates on idle and bad through all gears at all speeds and it does not matter if I am in park,neutral or reverse. So now replacing the bad mount ,my problem has just amplified!

Could anyone have any ideas what too do next or what it could be creating this bad vibration it would be grateful. Many Thanks

[GJB]

Check the vacuum supply to the mount is OK if this is not working ( only works at low revs ) will cause vibration.

[A lex]

You should not be changing to Poly mounts.

The whole idea of the mounts is to dampen the extreme vibration of the engine - poly mounts are designed to be stiffer and more rigid. Id imagine a brand new poly mount will provide far less damping than a knackered standard one.

Change the poly mount for a new OE spec mount and report back.

[JohnL]

Does the auxillary belt squeak as when idling, it could be the alternator overrun clutch in the pulley.
John

[familyman2]

Thanks for the replies, I can understand about the poly mount just thought as it was prone to go I was investing in not having to replace it for a while longer, will consider getting a OEM one after Crimbo or my kids will go without gifts lol. what i have done is tied the vacuum hose going too the front mount , and I am getting better boost, off the mark without as much hesitation, which makes me think the mount might be leaking. After I put the stiffer lower mount on it got worse which make me think again the vibration from the front mount is going through the subframe which is more noticeable now as the old one was shot and taking most of the vibrations itself. So I am thinking too replace the front mount hope that should do it, if it just reduces the vibration but has not gone completely I will change the lower mount too a OEM mount. Does this sound like a plan? does this make any sense at all?

Many thanks

[familyman2]

but the thing is if the front mount is not working it would be just low revs right?, but I have vibrations at idle and under load all through the gears and at any speed, its only when I put more acceleration on,could this still be the mount? I have read that the exhaust can drop onto the subframe if one of the mounts sag ? or it could be a combination of both? will need too check the exhaust next time I am free.

[JulesBadman]

Originally Posted by JohnL

Does the auxillary belt squeak as when idling, it could be the alternator overrun clutch in the pulley.
John

Sorry to hijack.....
I've just bought a '54 XC90 D with a vibration issue (good price). One of the things it had was a squeak from something being driven by the serpentine belt - the dealer is getting it fixed before I collect, he mentioned it was probably the alternator clutch bearing.

Can this cause vibration through the car throughout the rev range? Mine it's terrible, but it buzzes more than it should, you can feel it through the floor, steering and pedals.

Cheers

[Tannaton]

I didn't think the alternator had a clutch? Most likely culprit is the air con compressor which does have a clutch or the belt tensioner.

FYI it is possible to remove the a/c pump clutch in situ, dismantle it and replace the bearing without having to drain/regas the system. The bearing is about £10-£15 if you buy is from an engineers supplier or e-bay. You do need to make yourself a little puller though to get the clutch off.

This should be attended to a.s.a.p. because if the bearing seizes or collapses it will strip the belt which is likely to get caught in the timing belt when it snaps with very expensive consequences. Some people on here will have horror stories....

If you have a severe vibration coming from engine revs alone (i.e. not road speed) - that's more likely a misfire (injector/valves) I would suggest?

[cheshired5]

Originally Posted by Tannaton

I didn't think the alternator had a clutch?

Yes, it has an overrun/clutch pulley.
It squeals when it's on it's way out and makes the belt flap alarmingly.
If left, it can seize with similar consequences to the a/c pulley giving up.
They have a life of around 80000 miles so it's wise to change it with the aux and timing setup.
I did my alternator pulley earlier this year but having said all that, it doesn't cause any additional vibrations as described by JulesBadman.

[Ducklakeview]

Alternator has a one way freewheeling clutch to prevent the massive loads on the serp belt when the car changes gear (auto puts more load on as it's gearchanges are faster and on throttle) Without the clutch, the belt would have to absorb the strain of slowing the rotating alternator with every gearchange.

Mike