Knocking noise at rear - S1/OTS

[ralphr1780]

Last summer a knocking noise had started on the rear left, irregular and often when tight cornering right. The knock was clearly on the outboard, just behind my left ear (LHD).
My first suspect was the wheel-hub, changed the wheel and regreased the hub with no success. Successively then tightened the trailer arm and anti-roll bar and links, also no success. Checked the exhaust fitment, no issue; inspected the spring and shocks and bushings, all tight and dry clean...
This week as I am driving it more, the knock became more frequent and present when hitting small bumps.
Rechecked the suspension and noted couple of oil drips on one of the left shock absorbers springs, with a mist of oil on the shaft collar. So bugger found and replacement is due.
Car has SPxX adjustable all around, and I have been quite happy with these.
What would the right move now, replace all 4 rears? Boge (Monroe) or other?
Or be skinflint (green?) replacing only one if I can locate one similar?
for good comments as usual.

[ralphr1780]

Getting close to the 400 views and not one comment

[mgcjag]

Hi Ralph....you know the options so its your choice...find and fit one...or a set of 4.....if you just want opinions then I would fit one....Steve

[bitsobrits]

If one is tired/leaking, and if you don't know the exact milage on the rest of the dampers, then I would replace all 4. Only if the dampers are relatively new, and you're on a tight budget would I replace just one.

But are you sure it's the damper? If a damper is failing due to seals leaking, it would be unusual for it to make a metallic knocking sound.

[ralphr1780]

Thanks to both Steve's.
The dampers are not new and I frankly have no idea of mileage, they were on the car when I got it in pieces 10 years back. But the ride has been so good so far, and much better than the koni classics I have on the other S2, that is why I am hesitating. I can only be sure that the knock is coming from the leaking one when I replace it. So probably will swap with one the right side and see if the knock follows.

[abowie]

So probably will swap with one the right side and see if the knock follows.

Good idea. That will tell you what's up.

It seems that SNGB are now offering a Girling rear shock for about £60 as a replacement for the Boge units which are NLA.

I've had one set of GAZ adjustables (on my MK2 when I bought it) basically all fail completely despite looking pretty new. I have another pair on the front of my OTS and they seem fine.

I replaced the MK2 shocks with 4 Konis as at that time they were pretty much the only thing available. I'm in two minds on Konis as I think they are very expensive for what you get.

Martin Robey do list your Spax adjustables for £130 each, so you could try getting just one if you're happy with the current ride in your car.

EDIT.

4 Boge shocks for a very low price https://www.simplyperformance.com/shop/ ... rbers-5361 Bet they don't have stock....

[rfs1957]

Doesn’t sound like a shock absorber noise to me ……..

[40GT]

Can you not just remove the leaking shock completely and test

[ralphr1780]

Doesn’t sound like a shock absorber noise to me ……..

No other visible suspect.

[ralphr1780]

Can you not just remove the leaking shock completely and test

this would be quite risky in my view.

[40GT]

Extreme admittedly but I don't think it's the shock either.

[caveman]

Ralph,
Have you ruled out the drive shaft covers if fitted? More likely to grind than knock but worth a check.

If you're adamant it's shock absorbers, I would be inclined to remove one from each side and try on a known stretch of road that you have heard the knock. Then swap until you find the culprit. Go easy tho

[abowie]

Personally I wouldn't drive the car with any shocks removed.

The springs are intrinsic with the shocker. I think that if you tried to drive it with only 2 springs it could bottom out, causing damage.

I think the idea of swapping the suspect shock to the other side will make it clear if it's the culprit. If the shock is visibly leaking fluid it is unserviceable.

[caveman]

I had a slight knock on a front shock absorber 2yrs ago and it was easily replicated in the garage by bouncing up and down gently. Like you say, if there's oil evident that needs addressing and may well be the route cause overall.
I've checked my fhc in workshop with 2 socks off and the height drop is significant so ignore my last post

[Jack the lad]

I thought that the Spax adjustable shockers were gas filled? If so they would not leak any oil to make you think they were the culprit. I had this at MOT time when the examiner failed my car for leaking shock absorbers, I told him they are gas filled, he checked with the VOSA guys and they confirmed it and he had to pass it.
Modern MOT garages have had to fit equipment that shakes and rattles the car to enable them to test it without jacking up. Take your car along and ask them to put it on this and it should find the problem in 30 seconds. Quick £10 to the guy for a beer, job sorted.

[ralphr1780]

Update: I swapped the suspect left shock absorber with one of the right ones, the knocking is gone like magic and did not start on the right side... yet.
Will give it some time to see whether the knocking comes back, before replacing all 4.
Thanks for the response!

[RICHOT]

Let’s hope the knock has been resolved.
Keep us posted
Cheers, Richard