[tishobg]

Hello,

It's a suspension noise thing - but in the back of my 147. Have been trying to fix it for ages now and I have yet again hit a solid wall, so some ideas will be much appreciated.

Happens on speed bumps primarily. Happens only on the move. I can shake the car vigorously while stationary and there is no noise whatsoever. I even got a friend to bounce in the damn boot, but no cigar.

Noise:
Clip 1
Clip 2

What has been changed so far:
Bushes on all trailing arms - left and right - both of them.
Strut top mount - right side.

I'd say you can hear it 99% of the time on the right side - left barely if even does it. Started doing it after a long 1000-miles trip with 4 people and a full boot.

ARB links can be seen in this video: Clip 3 . They are a bit loose, but can they cause such a racket really?

Again, any input will be appreciated as that noise is killing any joy while driving. Even if it sounds like one of the already changed items. Thank you!

 

[johnlear]

It isn't all that hard to twist the ARB link joints (unless perhaps fairly new and thus still quite tight), so what you are doing isn't a good way to check them. Check by grasping one end of the ARB itself and trying to forcefully move it vertically up / down (then check the other side, obviously).

The stock rear ARB is quite weak, so it isn't hard to move an end vertically if the associated link is worn. Any significant link wear should be fairly obvious.

Regards,
John.

 

[Fruity]

As John said, aside from checking the rear ARB links incorrectly, they do produce a dry creaking sound.

The heavier clonk is obviously still there. Has the exhaust been checked- especially where the hanger brackets are? I want to eliminate exhaust bracket from touching car bracket.

Have you tried removing everything possible from boot including spare wheel and tools?

 

[Fruity]

Can you say exactly where it is coming from? Is it one side or another? Is it definitely from behind the rear seats? Have you tried lowering rear seats into load position or even removed rear seats?

 

[tishobg]

Thanks for the fast response and sorry for answering so late - I’m preparing for a surgery which takes up a lot of time.

Definitely right side as main culprit. Today I had a long drive and I noticed it makes a similar clonking noise over bumps on the road, as if something is loose.

Followed your advice on the ARB links - they move both vertically and horizontally(towards wheel and then towards the center of the car). Didn’t know they make a dry creaking noise. Does that horizontal and vertical play make them even more likely a suspect? Also checked ARB bushes in the middle, no movement at all when pulling as hard as I can by hand. I have history of the car from the past 7 years and they haven’t been changed in that period.

Sound feels to be coming definitely from behind the rear seats, as rear seat passengers can hear it behind them.


Boot has been emptied, seats have been lowered to help me identify it. It’s louder in the cold and mostly gone when driving in rain.

Exhaust has been checked and has no movement.

I’m not mechanically savvy but I’ve had a couple of trips to the garage about it with no success hence why I want to address it myself.

Also wanted to add - car is riding on sports springs.

 

[Fruity]

Noise from right side at rear means not likely to be exhaust then as it exits on the left and its routing goes to left just immediately behind rear footwells (so under front of rear seat).

Disconnect and tie up or remove rear anti roll bar links. If noise stops, that is the fault.

Failing that, have rear struts swapped side to side. Transfer all components. Only the top nut (inside the boot needs to be removed) so spring compressors are not needed. Before doing that, jack rear of car off the ground (on the subframe- if using a trolley jack) and place hands under rear wheel. With hands at 4 and 8 or 5 and 7 positions of a clock face, lift the wheel up with reasonable force. If there is loose movement and not simply compressing the spring, lift it sharply and release quickly to see if you can get it to make the noise. If it makes the noise, remove strut for investigation or better still, have an assistant look at the top of the strut piston rod in the boot to see if it moves up and down. It ot moves up and down, that could be the strut mounting (but you said that was replaced recently) so then I'd suspect the nut which tightens down on the spring to retain strut top mount (but this would have been removed and tightened back on) so I'd suspect the strut itself.

Before condemning a strut though, I'd remove the wheel and check very carefully for signs of fouling/rubbing anywhere around the strut.

 

[johnlear]

If there is any vertical or horizontal movement in any of the linkage joints (i.e. between the joint ball and the body of the joint), then the joint is bad. The joints allow rotation around multiple axis (within limits). There should be no motion that isn't a rotation. If the joints are all good, then it shouldn't be possible to manually move the end of the ARB vertically (at all). But, since the ARB is weak, it might possible to move the ARB end laterally, though this would be to do with flexing the ARB arm sideways (not wear in the joint).

Re Fruitys' suggestion of trying to move the wheel (and thus the whole strut etc.) up and down; you might find some movement at the very top of the strut where it fits into the chassis. All that Fruity suggests is worth investigating.

But also, the top strut mount has a short conically shaped rubber protrusion (I think it's a metal cone with a rubber covering) which fits into a conically shaped hole in the chassis. If the 'cone' at the top of the strut is worn then it may not be held securely in the chassis hole, so may move up and down with suspension movement.

The top of the strut is retained (in the chassis hole) by a steel plate, which secures the strut mount in the chassis. This plate is custom shaped for purpose, and has rubber bonded to its' underside. The bonded rubber is sandwiched between the steel plate and the chassis itself (with the mount beneath the chassis also forming part of the 'sandwich'). When the plate is fitted, my understanding is that the rubber is a bit compressed between the plate and the chassis, preventing unwanted vertical movement of the mount.

If this rubber were worn, then it may not be statically compressed correctly. Some vertical clearance may exist, and so movement of the mount may occur. This could manifest as 'clunking', caused by the rebound stiffness of the damper as the suspension goes into 'droop'. That is, when the suspension is loaded with static vertical weight then the rubber cone will be pushed into the conical chassis hole and be well seated, but if weight suddenly lessens (over bumps say...), then the damper will pull the mount downward until any clearance between the rubber / plate and chassis is taken up ('clunk'). When weight re-loads on the strut, the mount will move slightly upward until the cones reseat, with another 'clunk'.

Just speculating (i.e. I haven't tried the following, but it seems a possibility...); it might be possible to place some sheet rubber beneath the rubber (i.e. under the original rubber and above the chassis metal), to take up clearance possibly caused by wear. You'd be aiming to slightly preload the plate / rubber / mount as fitted in the chassis. You'd be wanting to avoid any added rubber sheet being too thick.

Regards,
John.

 

[tishobg]

I'm quite late, but recovery from surgery and work/university just had my mind somewhere else. I still want to update this thread, at least as future help to people and to thank for your input.

I jacked rear wheels and there wasn't any movement at the top of the strut where the mount is when moving the wheel up-down. Just springs compressing.

I sprayed with silicone the ARB bushes and ARB end links. Did so for 2-3 days, took the car for a 70-80 miles trip after which I left it sitting for a week and half while I was in hospital. Once I returned, the noise was gone. It's been a about 2 weeks and upwards to 200 miles all city with pot holes, speed bumps and whatnot and the dry creaking noise is gone. Only sometimes does a knocking sound occurs from either site, but nothing that loud, just the typical "as if something is in the boot" knock.

I'll take the car for new ARB bushes and drop links at some point in the summer and I believe the issues will be resolved. Even though there wasn't any visible movement when yanking at the ARB, It seems the bushes are shot and the drop links have seen better days.

 

[tishobg]

Noise from right side at rear means not likely to be exhaust then as it exits on the left and its routing goes to left just immediately behind rear footwells (so under front of rear seat).

Disconnect and tie up or remove rear anti roll bar links. If noise stops, that is the fault.

Failing that, have rear struts swapped side to side. Transfer all components. Only the top nut (inside the boot needs to be removed) so spring compressors are not needed. Before doing that, jack rear of car off the ground (on the subframe- if using a trolley jack) and place hands under rear wheel. With hands at 4 and 8 or 5 and 7 positions of a clock face, lift the wheel up with reasonable force. If there is loose movement and not simply compressing the spring, lift it sharply and release quickly to see if you can get it to make the noise. If it makes the noise, remove strut for investigation or better still, have an assistant look at the top of the strut piston rod in the boot to see if it moves up and down. It ot moves up and down, that could be the strut mounting (but you said that was replaced recently) so then I'd suspect the nut which tightens down on the spring to retain strut top mount (but this would have been removed and tightened back on) so I'd suspect the strut itself.

Before condemning a strut though, I'd remove the wheel and check very carefully for signs of fouling/rubbing anywhere around the strut.

Sorry to ressurect an old thread, but I have a question for you. The knocking persisted even after lubing the bushes and disconnect arb link. I went on a deeper investigation myself and found the source.

This video is taken where the top strut nut is. I'm lifting the wheel with force and every time I lift it, it makes a gap below the steel (covered with rubber) plate in the boot and the chassis. When the wheel drops back, you can hear the 'clonk' around the top strut mount. It's the replaced unit, but noise comes from there nonetheless - I'm 100% that's the source. Does the noise + movement indicate a bad strut mount or the strut itself or the steel plate in the boot? I doubt it's the steel plate as the clunking wasn't there before changing the top mount in the pursuit of fixing the creak, which turned out to be the ARB bushes, but still.
Link of video

 

[johnlear]

It looks like the nut isn't tight. I see vertical movement between the nut and the strut mount, so the damper rod isn't being held firmly in the stut mount. Tighten the nut, but if the nut can't be tightened (i.e. is already tight) then the nut could be bottoming out on the damper rod thread before the rod is properly 'clamped' into the strut mount (by the nut). If so then you might need to place a thick washer under the nut.

Regards,
John.

 

[bazzbazz]

It is definitely movement between the upper shock mount and the body. Normally I would say you have a badly worn upper shock mount, but you say you have already replaced it.

Did you replace it with the correct upper mount, as there are two types available, standard and sports suspension.

https://www.alfaworkshop.co.uk/parts/147_Shock_mounts_parts.shtml

 

[tishobg]

It looks like the nut isn't tight. I see vertical movement between the nut and the strut mount, so the damper rod isn't being held firmly in the stut mount. Tighten the nut, but if the nut can't be tightened (i.e. is already tight) then the nut could be bottoming out on the damper rod thread before the rod is properly 'clamped' into the strut mount (by the nut). If so then you might need to place a thick washer under the nut.

Regards,
John.

Thanks for the reply.

The nut is as tight as it can get it with my socket set. Impact would be better.

Perhaps the video isn’t showing it ideal, but by feel I can see it’s not movement on the thread as the nuts aren’t showing any movement, the entire steel plate lifts off the chassis to create a gap when I lift the wheel. It’s either movement between the top mount and chassis or steel plate not sandwiching the chassis and strut mount tightly enough. Each time the gap closes (when wheel falls in a pothole for example) it produces the knock on the strut tower.

My car has standard suspension as it’s a base model 147, therefore the garage installed SNR KB960.0.

 

[johnlear]

I wasn't looking at it ideal (viewing videos before properly awake, blurry eyed...).

Bazz is right, there is movement between the mount and the chassis. The mount fits into a 'conical' aperture in the chassis, i.e. it has a rubberised male cone section protruding at the top of the mount which fits a corresponding female cone shaped hole in the chassis plate. Vertical force pushes the mount hard into the chassis 'cone' until it can't move higher. To stop the mount falling out of the chassis hole there is a circular steel plate above the chassis hole which is larger than the hole. The circular plate has a rubber pad on its' underside which I think should prevent any downward movement of the mount, holding it securely in place with no unwanted movement. If the pad is worn or for whatever reason not thick enough then the mount won't be secure and there will be some free movement such as you have (but it can't fall all the way out).

My 147 has the same problem with one of it's rear strut mounts, but it isn't noisy and causes no problems that I can detect. It's only evident with the rear wheel jacked off the ground and manually moving the wheel and suspension up and down (about 1mm of vertical movement between the mount and chassis). If it ever does get noisy I intend to try adding some rubber sheet under the circular pad to tighten it up. It might work.

Regards,
John.

 

[bazzbazz]

Is this only happening on the side that the garage fitted the new mount to? How long ago was it replaced (Mileage/Time)

 

[tishobg]

Is this only happening on the side that the garage fitted the new mount to?

Yes, car is silence on all other 3 wheels. Checked them individually and in motion. Something wrong with the installation/mount. The steel plate which goes on top and holds the strut to the chassis was the same before the new mount and it wasn't knocking back then.

We only changed the mount as there was minimal play in the old one, yet no noise, but we were trying to fix an unknown knock so we decided to go ahead with it.

Garage will cover any warranty if needed but I want to make sure I don't bring the car with a claim and something else comes out to be the problem.

 

[bazzbazz]

Nice to see the garage doing the right thing. Take it back to them as there is definitely something amiss, can't work out what from the footage as there is not much that can go wrong with the mount except normal wear. Something has been assembled wrong here.

At least you have found out whats causing the knocking. :rofl:

 

[Fruity]

The only thing which comes to mind is perhaps when the garage changed it, they fitted a new nut supplied. If so, this is wrong. The nut holding the strut top on (under spring preload) is meant to be plain (not nylock). If a nylock was fitted (lower nut), I am sure the greater nut height will foul the top hat bush/plate which is inside the boot and the result will be movement and noise.

 

[tishobg]

The only thing which comes to mind is perhaps when the garage changed it, they fitted a new nut supplied. If so, this is wrong. The nut holding the strut top on (under spring preload) is meant to be plain (not nylock). If a nylock was fitted (lower nut), I am sure the greater nut height will foul the top hat bush/plate which is inside the boot and the result will be movement and noise.

Is there a way to inspect the lower nut without removal of the shocker? It should be beneath the chassis right on top of the strut mount so I doubt it, but hey, asking does't hurt. I have an endoscopic camera which might help.

The actual strut top mount that was fitted to my car does not come with a new nut in the packaging, therefore I doubt it was changed...

 

[johnlear]

Is there a way to inspect the lower nut without removal of the shocker? It should be beneath the chassis right on top of the strut mount so I doubt it, but hey, asking does't hurt. I have an endoscopic camera which might help.

Yes. With the cars' weight bearing on the strut, just undo the top Nyloc style nut and remove the circular 'top hat' plate. From the top of the strut (inside the car) you'll then be able to see and have access to the plain nut. The plain nut is the one which holds the damper / spring / mount together, the upper nut only holds the circular plate (the plate being what prevents the strut mount from dropping out of the chassis and prevents knocking when the suspension 'droops').

The plain nut needs to be of a certain thickness (or less), or the else the circular plate will be fitted too high, which would cause the looseness you have. I can't recall whether there is a washer beneath the plain nut, but if so then this also mustn't be too thick, for the same reason.

Regards,
John.

 

[jomor]

The plain nut needs to be of a certain thickness (or less), or the else the circular plate will be fitted too high, which would cause the looseness you have. I can't recall whether there is a washer beneath the plain nut, but if so then this also mustn't be too thick, for the same reason.

Regards,
John.

This may be the reason for this problem appearing more often with coilover installations