Help diagnosing a suspension clonk

[gridgway]

Has the car been on a "wheel shaker" - not sure of the correct teminology for that thing plate in the MoT test (or that centre gravity have)? That pinpointed a clonk that I had in my G50 hotrod (broken rollpin in the shock insert).
Graham

[911hillclimber]

Lubrication is key on the poly bushes and can deliver a good 'crack' if they decide to stick and get unstuck by suspension movement.
There is a special grease for these bushes, very very x 10 sticky and very hard to apply evenly but the grease does not migrate in use with other greases will, the grease will displace over time leaving you dry.

That insert top ring is well worth checking.

In KS's case, if removing the drop link on one side the anti roll bar is still being moved. Again, the rubber or poly bushes need the correct lubrication on assembly.

I've found polybushes a pain in the end and prefer oem rubber.

That special grease came from Elephant Racing in a small yellow tub (albeit 20+ years ago). You don't need to smother the joint but it needs a good even layer on assembly.

Just found the tub in the garage. It states:

LORAL Poly-Cons
Garwood NJ
Ontario CA

[jonno1]

We went with 21mm front and 26mm rear hollow torsion bars. Would changing the size of the fronts contribute to the clonk? I dont remember it clonking before we changed them, but then the car has undergone a fair amount of other work as well, replacing bushes, rebuilding the steering rack etc.

[911hillclimber]

Doubt it personally.
The splines are still the same, so the fits are the same.
Imho loose parts will rattle all the time until something falls off or similar.
Knocks and clocks etc are when things move substantially due to a high load and something is displaced to a new position such as a sticky bush etc.

This is a real irritation, so worth taking it all apart and check things as you re assemble, at least easier than doing the same to the rear....

I am at a similar position with a slight but very irritating wobble in the car much like wheel balance, and will have to do the same.

I have changed nothing though, just the tyres, and the wheels have been balanced to death.
Must be something else in my case.

[jonno1]

Well, this continues to elude....currently with a Porsche specialist who definitely agrees the clonk is from the passenger side front (LHD car)....but has had a good look, including removing the new Bilstein B6 damper and cannot immediately see what may be causing it (there is nothing obviously "loose")....they will remove the TB to see if it is correctly seated but it was indexed ok.....so damn annoying.

[Bruce M]

Remove the droplink from that side and re-test. That will eliminate a number possible causes... or not.

[jonno1]

Tried the drop link too.

Literally everything checked and nothing obvious. Unlike the heavy “clonk”.

So next we will replace the damper (which is relatively new) to see if its that. Which I doubt but desperation is setting in!

[Gary71]

Loose battery? Spare hammer in the smugglers box? Loose fuel tank? Bonnet hinges hitting the scuttle?

Just some unlikely random thoughts!

[jonno1]

Checked all that too!

[Lightweight_911]

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Loose bracket that attaches bottom of headlamp bucket to battery box ?

.

[jonno1]

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Loose bracket that attaches bottom of headlamp bucket to battery box ?

.

Its good, but its not right

[Bruce M]

Tried the drop link too.

Literally everything checked and nothing obvious. Unlike the heavy “clonk”.

So next we will replace the damper (which is relatively new) to see if its that. Which I doubt but desperation is setting in!

So you disconnected the drop link and drove it & the knock was still there? That eliminates the droplink, play in the bar “arm”, soft bushes, undersized bolts, etc, etc.

[911hillclimber]

And do the same with the rear, sounds travel at times.
Change one thing at a time to find the source.
Good luck, frustrating to sort, but better than sorting a water leak...

[Mick Cliff]

...do the same with the rear, sounds travel at times....

That is so true! A few years ago my 911T developed a knock that was 'obviously' coming from the front left side whilst travelling back from a visit to the Nurburgring.
Several weeks of intermittent ferreting around the front suspension failed to identify a source. I'd got to the point of maybe thinking it was something loose under/in the dash - no joy there.
Up on a ramp idly checking the rear suspension I discovered that one trailing arm (left side) bushes had disintegrated, allowing the arm to move longitudinally.
Engine out job to access the bushes! I still hadn't connected the front end knock to these bushes but lo and behold that WAS the source of the knock.

[gridgway]

I may have missed it in the description, but how do you make the problem actually happen to hear it? Do you need to drive? Or can you do it statically?

That youtube chap Number27 with the 308 used a multi microphone gizmo to try and get to the bottom of some noises in one of his vids. That might be an idea?

Graham