Mystery knocking - NSF 987.2 Cayman S

[dunc_sx]

• ** SOLVED - See below ****

Front left knocking / thump over bumps & pot holes.

Recently changed:
New dampers and springs 1,000 miles ago (B8 & Cayman R springs)
New LCA and tuning fork 20 miles ago
New drop links 3,000 miles ago
New strut top mount 9,000 miles ago
New inner and outer track rods 2,000 miles ago

Car has 106k, the noise started approx 300 miles ago.

I thought this was the lower ball joint, as did the garage I took it to but it's still there despite replacing.

My only thoughts are - the ARB is misbehaving (mounts or drop links again) or the top mount is away again although it was inspected when the dampers were changed.

Anything I'm missing?

Thanks,
Dunc.

Edited by dunc_sx on Sunday 14th August 13:09

[53x11]

I've recently been pulling my hair out over something similar. 987.1 with 82k and fully refreshed front suspension.

After a lot of 'wheel off, check something, wheel on, test, repeat' I found it was a combination of the lower drop link nut not being f****g swing on the spanner tight and the three top mount nuts taking an extra 10 degrees of 'nip up' over the correct torque.

I loosened the drop link nut to test the theory and driving the car with anything less than a really torqued up nut resulted in suspension sounding like a washer on full spin with a brick in it!

Hope this helps.

[Discombobulate]

dunc_sx said:

Front left knocking / thump over bumps & pot holes.

Recently changed:
New dampers and springs 1,000 miles ago (B8 & Cayman R springs)
New LCA and tuning fork 20 miles ago
New drop links 3,000 miles ago
New strut top mount 9,000 miles ago
New inner and outer track rods 2,000 miles ago

Car has 106k, the noise started approx 300 miles ago.

I thought this was the lower ball joint, as did the garage I took it to but it's still there despite replacing.

My only thoughts are - the ARB is misbehaving (mounts or drop links again) or the top mount is away again although it was inspected when the dampers were changed.

Anything I'm missing?

Thanks,
Dunc.

Worse when the car is hot by any chance?

[dunc_sx]

53x11 said:

Stuff +
Hope this helps.

Thanks 53 - I'll investigate these areas

Dunc.

Edited by dunc_sx on Saturday 13th August 06:55

[dunc_sx]

Discombobulate said:

Worse when the car is hot by any chance?

No exactly the same, what were you thinking out of interest though?

Cheers,
DUnc.

[Discombobulate]

dunc_sx said:

No exactly the same, what were you thinking out of interest though?

Cheers,
DUnc.

Ignore me. Ball joint in control arm - even a new one (happened to me with OEM part).

[dunc_sx]

Ok thanks for that, I'm going to have a good look at this today so fingers crossed I find something.

Cheers,
Dunc.

[Pope]

My money is on a worn roll bar; the bushes seem to last forever but take some diameter from the bar over time. Raised on a lift the bar is under some tension so a wobble and shake of components rarely shows it up; disconnect the droplinks and tie them to the damper and give it a drive (or remove completely and test).

[dunc_sx]

Thanks Pope,

I've actually just disconnected the left drop link and then a road test, same noise is present. There shouldn't be much force on the ARB with only one side connected but that's still possible.

They are poly ARB bushes and cosmetically good, I'll give them a pry bar and check for movement. If required I could always just remove the ARB completely to completely rule it out as you say.

The thing that's putting me off it being the control arm ball joint is it was an identical noise pre and post new control arm meaning the new one would have to be worn out by the same amount as the old one.

I think it's floor panel off next for a good look around, deffo far LHS nise though.

Cheers,
Dunc.

[Pope]

Had a bit more of a think; could it be the fuel lines in the tank?

I have had a few strange cases where the pick-ups and level sender can clank about in the tank and cause hollow knocking sounds over bumps. Hit the bottom of the tank with your hand - does it make similar noises?

[dunc_sx]

Solved - Top mount is goosed - 15k and less than 3 years since it was replaced by previous owner (my initial estimate was a bit off).

Thanks anyway Pope and others, ordered a new one inc. bearing and drop link while I'm here (and caliper bolts)

Easy fix at least, the front ARB looks like it would be tricky to remove btw - Glad I didn't attempt it.

Cheers,
Dunc.

[dunc_sx]

Probably not what you want to hear but I just went ahead and removed it. I had ruled out everything else and I've got a 1,000 mile road trip around Scotland with fellow enthusiasts soon so urgently needed it fixed.

The bearing is fine so it was not identifiable through steering input but the bush itself was starting to self destruct so the sleeve is moving in relation to the strut top bolts (if that makes sense).

Basically exactly what the Matt video above shows but less severe in my case.

Hope this helps, completely rule out the more obvious stuff first though.

Cheers,
Dunc.