Help diagnosing a suspension clonk

[hot66]

looks like a bilstein strut ... is there a roll pin at the bottom of the housing like this ?



if it is , then there is a bush at the top of the strut housing , if this is worn it can allow the insert to move and *might* cause a knock

[gridgway]

And with the correct orientation of roll pin too. I had one in the wrong way and it broke quite quickly which (as it turned out) caused my suspension clonk!

When it was put on Center Gravity's shaker plate thing we found the noise.

Graham

[jonno1]

I cant see anything like that - is it obviously visible with the strut fitted on the car?

[bjmullan]

Have you thought about trying a Electronic Stethoscope Kit? The one below has 6 channels and can be had on ebay for £80.

https://www.amazon.co.uk/FreeTec-Electr ... B076MTHDDW

[hot66]

yes easy to see above the ball joint .

Did you buy the new inserts ? If you did you will know which ones you bought .. bilstein inserts for boge struts, or bilstin inserts for bilstein struts .. theyre very different from each other.

[jonno1]

Just checked garage invoice

They fitted these:

https://www.design911.co.uk/fu/prod3187 ... =doofinder

[hot66]

Boge strut

[jonno1]

So strange its just the one side....

[911hillclimber]

That will answer a few questions!

[jonno1]

That will answer a few questions!

I am not sure I have any idea what questions there are left to ask on this...

[911hillclimber]

If the base of the insert is impacting on the inside of the casing while on the move, you would not feel it in the garage pulling on everything.
James could have you on the right track.
However, also a question, why only on one side, other side must be tight or tight enough?

[jonno1]

Two professional garages have now removed and installed the damper. The latest a Porsche garage....they say that the whole thing is tight, as it should be etc. Could they have missed something?

[911hillclimber]

The Bilstien strut uses the 'C' pin to lock the rod to the bottom of the strut and is a (very) interference fit, hence Graham's post on it being installed to the correct orientation as James' pic.
This gives zero play at that connection, hence no noise.
Obviously something has to move to make a noise.

At the top of the strut body the insert is locked in place, the body of the insert is a much larger diameter than the slender rod located by the C pin. There is a guide there not a big clamp nut as below:

On the Boge design it is all opposite, the bottom large diameter body goes into the strut and the blunt end is locked down into position using a large (about 50mm dia) nut which needs to be tight. The slender piston rod extends to the top mount.

iirc you cannot put a Boge insert to a Bilstein strut, but nowadays maybe you can by a Bilstein to fit a Boge strut?

An experienced Porsche 911 specialist would be looking into this by now, so all this may be red herring, however, I would pull it all apart and go through all these details bit by bit and looking for clues of movement howsoever small in these simple assemblies as it comes apart.

If you have Bilstien struts and bil inserts you must check that C pin as it is the only part that locates the two tightly together.

You need to be sure the Bil thin piston rod has the groove in it aligned to the C pin hole. The C pin is an interference fit to the strut hole AND the insert piston rod.

In this picture the groove can be seen on the left, the C pin has to pass alongside the groove and the strut.



Here is the Boge design showing the large clamping nut used.
I also note thatere is a Bilstein insert for the Boge strut, but the body design and orientation are identical.

[911hillclimber]

To be sure the Boge insert is fully clamped into the strut there needs to be a gap between the under face of the nut flange and the strut, ie the nut has not bottomed-out.

If the nut it up to the strut top the nut will be tight but the insert could be loose = ability to move= noise.

[jonno1]

Thanks v much for such detailed advice.

Any special tools needed? Anything a relatively competent home idiot could take on or best left to the experts?