Playing “what’s that sound” when it comes to cars (or helicopters) is akin to playing “what’s that smell” in a landfill.  It’s very difficult to say the least, but sometimes you just get lucky.  I had been hearing a knocking/clunking sound since my M Coupe’s suspension overhaul, emanating from the front left suspension.  It was only present when going over very rough roads, like rail crossings or curbs.  It was present on my first track day, as my instructor noticed it asked some questions like “how new are your end links.”  All the parts were either new or had less than 30k miles, so I doubted it was a failing component like a ball joint.  I checked all the torque underneath the car for where the knuckle attaches to the strut, and the lower control arm as well.  Everything was tight.  Then I had a thought: what about the top nut for the strut?  Popped the Z8 plastic cover, and sure enough, I could spin the nut freely.  Keep in mind it was originally torqued by hand, but a split washer was used.  Fortunately this is a quick fix: jack the corner up, disconnect the end link, remove the three strut hat nuts, and swing the strut out from the wheel well so the top nut can be accessed.  I hit it with the air impact this time, then added torque stripe to both sides to monitor any further loosening.

Right Strut HatI know it is stamped “L” but my hats are swapped, this is the right side and is still torqued correctly.

Left Strut Hat
This is the left hat, completely loose.
Strut
Strut swung out from tower to access the top nut.  Bottle jack used to raise control arm to align end link.
Torque Stripe the NutAdded orange torque stripe to the nut to easily check for it backing off.

After this quick fix everything was good to go.  No more clunking noise.  Fortunately the nut never became completely unthreaded, which could allow the entire shock rod to come out, basically losing the upper connection for the suspension.  No doubt the sway bar did its part of keeping the strut somewhat in control.

 

 

 

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