Mystery suspension clunk

[honestjoe]

I tend to agree that its the rear of the car..any clunks or knocks on the front end are very audible to thier location..the rear is a different kettle of fish...there is a lot of bushes as you know..my axle bushes were trashed beyond recognition but showed no apparent symptons other than clonking..and perhaps the car sitting a little low..the forces exerted on the various bushes are hard to recreate by investigation alone..but the all too familiar sound is evidence that at least one of them is on its way...look forward to your findings clifford...ps..I"m beginning to wonder just how long my aftermarket axle bushes will really last..12yrs?...i think not!!..cheers hj.

[Clifford Pope]

Update:
I had a thorough look lying under the car at the weekend, lifting the suspension up and down and levering things with a long screwdriver. I couldn't see anything amiss, so I have tried swapping the rear left hand shock absorber.

The squeaky noise has vanished on that side (they are heavy duty shocks with integral external springs, but the spring is a close fit over the thick ribbed plastic body of the shock absorber, and squeaks loudly as it scrapes).

The clunking noise has greatly diminished, but is still there.
The odd thing is the replacement shock absorber barely worked when I first installed it, but over the course of a few hundred miles it has recovered its resiliance, and also the noise is slowly diminishing. Is that normal with a shock absorber that has been stored horizontally - it needs to be re-activated in the normal vertical working position?

At least, it seems to point to the noise being largely an internal one in the shock absorber. I'm going to get a pair of new ones anyway.

[Old_Car_Driver]

I've just replaced the rear shocks and I now have an annoying rattle/clunk over pot holes and un-even roads. The shock were supposed to be OEM, but I noticed that the sleeve that goes over the M12 bolts at either end was not a snug fit, so I am assuming this is where the noise is from. Anyone know a cure for this, there is not a lot of play, but enough to rattle

[Clifford Pope]

Further update:

Noise cured - famous last words.

It seems to have been a combination of 4 different causes, each capable of causing a noise on its own, but all inter-reacting.

1) There are I discover two very slightly different sizes of lower shock absorber bolt, the one in the trailing arm. One is a snug fit in the metal sleeve, the other is very slightly thinner. Using the thinner one puts more emphasis on the tighness between the TA sides.

2) Don't rely on the TA sides flexing enough to squeeze the shock absorber bush and the metal spacer. I ended up finding a very thin shim/washer to make up a tight fit.

3) The nearly new shock absorbers were noisy. Apart from squeaking, there was a slight clunking noise from inside.

4) The bolt holding the rear of the anti-roll bar to the TA is not very secure. It doesn't have a hexagon head, but relies for tightening on its square shank staying firmly between the prongs of a slotted mounting plate. If the bolt is not really tight then the bar shifts its position sometimes, putting a different strain on the other fixing bolt, ie the long bolt also holding the shock absorber.

[Old_Car_Driver]

This is interesting what you say about the shock having a different dia hole at either end. I tightened up the TA bolt, but like you say it may need a shim or washer to prevent it rattling. If this works on my car then I will be very happy, the clunking is really annoying.

[Clifford Pope]

It's the bolt, not the bush hole diameter, that varies. I only found out when I was looking through my box of old miscellaneous bolts from previous cars, and found some with the same thread and hexagon sizes, but about 0.1 mm difference in bolt diameter.
That makes a perceptable rattle, and puts more emphasis on the need for the bush to be really squeezed between the sides of the trailing arm.

[Old_Car_Driver]

That makes sense, I replaced the bolt as I had to cut the old one to get it off. I replaced it with a Hi-Tensile M12, which fitted the old nut fine, but if the middle of the bolt is slimmer that would explain it. At last I can stop re-building it now I know the cause, I was about to replace the shocks