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Quiet knocking noise

Alfred996c2

Trainee
Joined
27 Oct 2023
Messages
60
Hi all

I have a couple of small niggles and looking for advice as I suppose they could be linked?

My sunroof, when fully open makes a knocking noise over bumps - actually quite an agressive one. It's had a new motor, but feels like something isn't locking it into place when fully opened. If I close it an inch from fully opened the noise is 100% removed which is why I think it might be some type of support/click - any ideas would be amazing ( I have not removed the headlining yet, and if that is the route, I'll take it to a garage I think)

The second issue is also a knocking noise from the rear. Car has new poly bushes throughout (c. 5k old) and new bilstein suspension, c. 5k old.

Generally quite quiet over bumps, its around long corners like roundabouts, if I go from left to right I get a small clunk almost like a sliding clunk.... sometime reversing in a corner does the same and recently its getting more obvious on smaller corners.

I checked the sway bars and tried to tighten with a wrench, but little to no movement.

Any thoughts what I should be checking and tightening?

Thanks as always!
 
On the rear it sounds like one of the eccentric bolts for the coffin arm/toe arm adjustment may not be tight. You can easy spot this as you can see where the bolt has been riding up and down in the subframe here:
 

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Thanks Alex - just checked - quite rusted and doesn't appear any movement.... Thanks again
 
Did you try both on that side? Coffin arm and toe arm?
 
Morning Alex - yes tried both - the only thing I could seem to tighten were the sway arm bolts.

I tried an impact wrench on the toe arm eccentric which didn't appear to move it. I think I might need to drop it by a garage to check it over....

Any other thoughts very much appreciated
 
There'll be play in an arm or a link. The only real way to diagnose it is to disconnect one side completely from the car and then try moving it and feel for any play. Likely candidates are the ball/socket joints on your coffin arm, toe arm, and the support arm that runs diagonally to the coffin arm.
 
Interestingly, I went for a drive yesterday and tried some sharper left to right steerings at c. 50 mph and the knock is quite apparent - perhaps I've never really noticed due to mainly motorway - longer A roads.

I've checked over the bushings and they still look clean and purple....

Thanks
 
As I said, it'll be a worn ball joint in one of the arms or drop link.
 
As I said, it'll be a worn ball joint in one of the arms or drop link.
I concur, my 997 had covered 82.000 miles when I purchased it. A number of noises on cornering, they did not look it from visual inspection but a number of the rubber bushes in the coffin arms were toast. There have been cases of coffin arms giving up the ghost after a short mileage
 
I concur, my 997 had covered 82.000 miles when I purchased it. A number of noises on cornering, they did not look it from visual inspection but a number of the rubber bushes in the coffin arms were toast. There have been cases of coffin arms giving up the ghost after a short mileage
Unlikely to be bushes as the OP is saying he has changed them to poly. Therefore these should now last forever. The ball joints can wear out and develop play but I don't know if they will clunk.
 
Sorry for the slow response Alex, I broke my foot so energy has been spent trying to recover and completely forgot to respond.

Thank you - I'll have to wait until it goes in for a service now I think.... thank you
 
Hi Alex - just looking under the car again, and a friend has pointed out that the sway bar bushings look tired and quite dry. Would worn sway bar bushings cause a quiet knocking noise?

Cheers
 
Yes they can do, but you can usually rattle your sway bar up and down and see the play if its them. To rule it out, an easy fix is to remove the bushing cover and remove it, remove the bush, wrap a few lengths of insulation (or other) tape around the bar to increase the diameter, then put it all back together. This will take any play up and you can take it for a test drive to see if its gone.

Alex's free fix of the day :cool:
 
Hi Alex - thought i'd update you on progess. I got the car up and rear wheel off - nothing loose at all, tried gentle tap with rubber mallet - all rock solid.

So went around with a wrench to see if any bolts loose - the top coffin arms had approx 1/8th turn in them to c. 100 lbs. cant remember exacts.....

The rear right drop link appeared the loosest nut and having looked online I saw the torque was c. 40 lbs but people say tighten them as much as possible. So I gave it a good tighten to c. 80/90 lbs - went for a drive a knocking largely gone however felt something from the left. Jacked up and repeated on the drop link, this one was very loose. (but like the right, not loose when trying to wiggle - but perhaps that's the issue when trying to work off of the floor) so tightened up and on my next outing I'll report back!

Thanks again
 

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