Terrible Suspension Grinding Noises

[Gav]

within the last couple of days my car has started to make some terrible grinding noises from the left hand front suspension.

initially it was noticed going round roundabouts (with a full load) but now i notice it going over speed bumps.

with experiments i have discovered it is worse either:

1. on the down bump coming off the speed bump with front wheel.

2. if i just catch the cambered side of those smaller speed bumps with the left wheel. this noise is really bad so i wont do this anymore. if i get the left wheel wholley over the bump it is as 1 above. If i get only the right wheel on the bump there is no noise.

the noise is such that i am slightly worried about a major failure soon, but can anyone pinpoint anything for me to replace first?

[Peter.N.]

Hi Gav

Is it doing it all the time or just under the conditions you describe? If its a continual 'grind' rather than a rattle, it points to the wheel bearing although they dont usually fail suddenly and dont make all that much noise when they do. I assume you have checked the brake pads. There are several things that can cause a 'rattle' rather than a grind, the anti roll drop links or steering ball joints for instance. Without actually hearing it, rather difficult to diagnose. Could we have a recording?

Peter.N.

[Gav]

i'm not sure a recording is possible, i can upload pics, not sure about sound.

the situations i describe will always produce a noise. during normal driving nothing can be heard, with the exception of occasionally whilst on roundabouts (if heavily loaded or i'm booting it)

the car has 170k. A 2nd hand strut for fitted 20k ago as was the little upright link, and I've always had uneven wear to the outside edge on that wheel, before and after these new components.

pads are ok, replaced recently.

i'm maybe guessing its something like the bushes on a link somewhere but would really like to know where to start, or what is common before ripping it all to bits.

what other components are readily changeable around the suspension, having done the strut and link already?

[xmexclusive]

Hi Gav

It may sound silly but do a couple of simple checks. First for tyre pressure as one tyre way out can make the suspension do very funny things. Second have a good look round the rear suspension arms just these are loading very unevenly and upsetting the loading on the front suspension. My logic comes from having a half pressure front tyre that caused heavy rear wheel squeal on the diagonally opposite corner.

Regards

XMexc

[Peter.N.]

If nothing is heard in normal driving that probably excludes the bearing unless it has had some unusual type of failure. Probably the best thing to do is jack up the n/s wheel and see if there is any movement in the bearing, you will feel a slight ammount of movement but it shouldnt exceed about 1/8" at the edge of the tyre. If there is more than that, the noise is probably caused by something making contact with the wheel or brake disc. Does it make this noise when you brake? just wondering if you have lost a pad lining.

Peter.N.

[Gav]

cheers guys for the comments.

i have ruled out a few things so far. the brakes are not a problem - even wear on both pads, nothing touching, and no unusual sideways pull during braking. Also, no noise during any braking.

the tear pressures i have always kept a close eye on because of the uneven tyre wear. all four retain pressure well. i tend to up the front pressures a little to 36/38 to try to compensate for the tread edge wear. (failing!)

i can not get any nasty noises to repeat themselves except how described earlier.

i checked the strut for a rusty head (again) but no problems as yet. spheres are all brand new recently also.

there is no obvious clash with anything, such as the lining. all is clear.

i am puzzled most by the noise coming most when i go over the side camber of a speed bump. it's as if the sideways push on the tyre is causing some serious mis-alignment.

as for the bearing wear, i'll go and check for movement now...

[Peter.N.]

Well, if its a grinding noise which sounds as though it is being caused by wheel rotation I cant think of anything other the bearing, unless of course the driveshaft nut is loose. This uneven tyre wear, is it just on one edge, if so which one, I assume the other tyre is wearing normally.

Peter.N.

[Gav]

good point, i'll get the wheel off and check the nut also when i get out there.

the tyre wear is just the outer edge of the near side tyre. Has been ever since i've had the car (50k).

possibly a red herring to my issue, but i know i need to grease the height corrector mechanism and i am suspicious of it even more now because the suspension has just started to jump violently when moving suspension position up/down so something is sticking. whilst driving it behaves normally if mostly in hard mode nowadays.

[Gav]

just checked the car. taken the wheel off and there is nothing obvious loose or broken. there are no signs of any cleaned areas where touching may have occurred.

the wheel nuts were all tight, the driveshaft nut is not loose, nor has the retained cap been dislodged. there is no huge amount of give.

the only slightly different issues i can find compared with what i rememeber as normal is the car drops quite suddenly when lowering the suspension, especially to lowest. the rear is smooth but the front quite abrupt. it raises smoothly.

also when jacking the car up from normal height, the wheel did not lift with the car (i remember it raising with the car in the past, although i normally jack from highest setting) and i could smell lhm but there is absolutely no sign of leakage, nor of the level reducing.

also the photo shows the lower wishbone bush which appears to show lots of cracking of the rubber... is this normal to the eye?

[onthecut]

Hi Gav.

Have you had a good look and shake at both the CV joints ? Did the grinding start soon, or straight after any of the jobs you have done ? I can understand clonks, knocks and bangs if it's a hydraulic issue, but grinding definitely sounds rotational. Picking up on xmexc's point, have you also had a good look in the rear arches and at the rear wheels in general. If you have a shedload of play in the rear arms it might produce unwelcome noises.

Mike.

[xmexclusive]

Hi Gav

With a hard front suspension you need to examine the underside of the rubber strut top mounts from the wheel arch. This is a totally different mode of failure than the rusting seen from the top. Rock hard front suspension driven hard can destroy the mount in weeks rather than the years that top rusting takes. Have a look at the black insulation under the bonnet where it is over the strut heads. If it is worn away the strut may be hitting the bonnet.

Regards

XMexc

[techmanagain]

If there is any wear on the wheel arch mud "guard" caused by the front tyre touching it when turning or bouncing, I would definitely change the wishbone bushes on that side. It can produce a terrifying noise if they are well worn.

[Peter.N.]

Is the 'grinding' only there as the suspension is moving up and down, does it stop when the ride height is stable. If so it could be the lower balljoint or suspension arm bushes, in which case I would have thought you would have heard it when the suspension rises. This is a new one on me, not had it in 10 years of XMs, although I am pretty sure if I heard it, I could have a good guess as to the problem. Where are you located?

Peter.N.

[jorgy9]

What about the wheel, have u checked for cracks (I assume it's alloy).

Whatever it comes out to be, the simple fact that it's at the left-hand side probably means it's a result of steady stress on that side as it gets all the effort on roundabouts, which are all..right turns. Now, driving an XM in hard mode long term, should be forbidden by law...for the reason xmexclusive says. Please, if you are unable or simply don't aim to get down to trace and fix the problem, please at least put it in permanent soft: u do this by unscrewing and opening up the electrovalve and swapping the position of the 2 small and large springs u'll find inside. The large spring will keep that valve open at all times -no matter what the electric signals are- so the high pressure will be permanently passing through and pushing open the valve that's opening the middle sphere. You just need 2 hours on a ramp for that job and it could save you from the worse.

regards
George

[Peter.N.]

Hi George

That's a useful tip! I was trying to work out ways of keeping the coil energised without burning it out! You learn something every day!

Peter.N.