997.1 gt3 rattling / clunking sound left front when warm

[9971gt3]

I am having clunking sounds from the front in my 997 gt3. Appears to be only when warm after a period of driving. I even hear if right after I stop sometimes.

Heres a link to similar sound. Any thoughts?

https://www.youtube.com/watch?v=tjaL8hDVUzQ

https://www.youtube.com/watch?v=1c_v83XU548

[STiG911]

Morning!

Most likely culprit is either or both of the strut top mounts.
If it's not those, second suspect would be the anti roll bar drop link(s)

[Slippydiff]

From 2016 :

Slippydiff said:

It'll be one of the following :

1 The spherical bearings in the strut top mounts are worn .

2 The anti roll bar drop link ends (balljoints) are worn.

3 The front strut damper rod bushings are worn (frequently gets worse after a few miles driving as the dampers heat up)

4 Front coffin arm outer balljoints worn.

5 Anti roll bar bushes worn or dry.

6 Coffin arm inner bushings worn

1,2 & 3 (or combination of all three) are common issues.

Most OPC's will fail to or wrongly diagnose issues 1,2&3. Bite the bullet, book the car in one of the well known and regarded specialist Indys, or if you want the car set up and fettled to a standard few others will attain, book it in with Chris Franklin at Center Gravity.

HTH.

[9971gt3]

Thanks. Sometimes I can hear the sound when stopped. Does that help to sort out which problem it is?

[Slippydiff]

9971gt3 said:

Thanks. Sometimes I can hear the sound when stopped. Does that help to sort out which problem it is?

Stationary but turning the steering wheel ? Or stationary but releasing your foot off the brakes after having applied the brakes ?

[9971gt3]

I am 99% it was after releasing the brakes. Dont think the steering affect the sound.

Also hear it if braking hard or accelerate

[FarQue]

9971gt3 said:

I am 99% it was after releasing the brakes. Dont think the steering affect the sound.

Also hear it if braking hard or accelerate

Don't ignore the 'tuning forks' or 'forked arms' - although our 997 is a Carrera S rather than a GT3, the NSF tuning fork arm was causing a quiet, but distinct, knocking noise when puling up slowly at, say, traffic lights.

The joys of multi-link suspension on a 911 with a few years/miles on it...

[Slippydiff]

9971gt3 said:

I am 99% it was after releasing the brakes. Dont think the steering affect the sound.

Also hear it if braking hard or accelerate

It could be the brake pads rattling in the calipers due to the adhesive on the "stickies" that stick the pad backplate to the caliper pistons, having failed due to overheating.

But it's just as likely to be the coffin arm outer balljoints having dried out, likewise the same (balljoints) on the anti roll bar droplinks or indeed the diagonal compression struts.

As I mentioned in my earlier quoted post, you really to need to find an independent who's familiar with the GT3's front suspension, in order that they diagnose it quickly and accurately, otherwise they'll end up bolting on lots of new parts that they think may be causing the issue, but all too frequently isn't ...

[Richard-cqpvd]

I’ll go with tuning forks, my 996 had similar. No noises or play when cold but definitely knocking after driving some way and the suspension joints had warmed up.

[Richard-cqpvd]

I’ll go with tuning forks, my 996 had similar. No noises or play when cold but definitely knocking after driving some way and the suspension joints had warmed up.

[Richard-cqpvd]

I’ll go with tuning forks, my 996 had similar. No noises or play when cold but definitely knocking after driving some way and the suspension joints had warmed up.

[Slippydiff]

Richard-cqpvd said:

I’ll go with tuning forks, my 996 had similar. No noises or play when cold but definitely knocking after driving some way and the suspension joints had warmed up.

The tuning forks are also referred to as "diagonal arms" or "compression struts", hence I mentioned them in my post above

[rrroro]

Centre Gravity diagnosed a similar noise on my 997.1 GT3 several years ago. From memory it was the "DU bushes" in the front dampers, which (I think) could be item no. 3 in Slippy's list above

[Pope]

Check between the anti-roll bar and the subframe for a stone or similar; have seen where they get taken into the undertray and then fall down between the bar and the frame. As the bar turns relative to the frame the stone gets ground into the adjacent parts causing a noise very similar to that in the first video - especially if it just started randomly.

[9971gt3]

Many thanks for help here.

I forgot to mention that the car was just at Porsche center one week ago the same day I bought the car.
And they could not find anything at that moment. It was in the days after on the transport drive home we heard this strange sound several times.

Porsche center now confirm that they did a normal service and checked the suspension, brakes, control arm etc last week. They could not find anything

I took it for a 30 minute drive yesterday and the knocking sound was gone.

I think the sound occur only in low speed after longer driving at higher speed and/or after hard braking/ acceleration

[Slippydiff]

9971gt3 said:

Many thanks for help here.

I forgot to mention that the car was just at Porsche center one week ago the same day I bought the car.
And they could not find anything at that moment. It was in the days after on the transport drive home we heard this strange sound several times.

Porsche center now confirm that they did a normal service and checked the suspension, brakes, control arm etc last week. They could not find anything

I took it for a 30 minute drive yesterday and the knocking sound was gone.

I think the sound occur only in low speed after longer driving at higher speed and/or after hard braking/ acceleration

Hence my suggestion you should get the car checked over by one of the well regarded independents. they'll have both the time and inclination to establish where the noise is coming from and rectify it cost effectively.

[ttdan]

rrroro said:

Centre Gravity diagnosed a similar noise on my 997.1 GT3 several years ago. From memory it was the "DU bushes" in the front dampers, which (I think) could be item no. 3 in Slippy's list above

This was a known fault back in the day. I had new dampers under warranty. You can only hear it when the cars is warm and on a slightly uneven surface at slow speed. Any real load in the suspension and the slack is gone and you won’t hear it.

[Retept]

Agreed, it will be worn bushes in the Bilstien shocks. Had this issue with mine. Sent all four shocks back the Bilstien UK for a full referb, no problems since.

Edited by Retept on Tuesday 22 March 22:34

[Slippydiff]

ttdan said:

This was a known fault back in the day. I had new dampers under warranty. You can only hear it when the cars is warm and on a slightly uneven surface at slow speed. Any real load in the suspension and the slack is gone and you won’t hear it.

This ^
Some years ago Bilstein developed modified DU bushes (different material and a design that increased the surface area) to address the issue.
However, the noise the OP demonstrated in his videos didn’t sound like damper rod bushes to me.

[9971gt3]

Thanks guys.

I will do a test drive with chief tech at the most "experienced with gt cars" porsche center in my country. He said exactly what you said about not changing the whole front We dont have any independent workshops like the ones you have I think.

The car had sat for almost 2 years with little use before I bought it. The brakes was screaming like hell and also some rattling sound while braking and I did some hard braking after a while the first day after picking up. Then the sound from the brakes went away for a period. But still screaming from time to time.

The day after, when we came off the highway the new strange sound appear for the first time at low speeds.