Knocking @ front

[somersetdub]

Hi all,
I have had my Passat for a few years now and I love it. Around a year ago I decided to treat it to a set of Bilstein B4s with Eibach springs, along with a complete set of genuine VW suspension arms, including ARB links and track rod ends.
Ever since then, I have had a knocking noise coming from the front end when going over certain bumps only.
I have chased this problem ever since and it's driven me mad. I have since replaced:
Front wheel bearings
ARB bushes
All engine mounts and gearbox mounts
Both undertrays and all fixings
The exhaust front pipe because the flexi was weak and blowing slightly.
All the subframe stretch bolts, torqued correctly.
The front discs and pads have been upgraded to 312mm with genuine items and don't rattle.
The top mounts have been replaced and I've taken the struts off to check the top mount nuts several times out of desperation!
The list goes on.
I have checked and rechecked everything and can't find anything wrong. I am actually qualified mechanic and have got a couple of mechanic friends to check it and they haven't been able to find anything.
The noise only seems to happen when the front wheels drop quickly for example in some pot holes and certain speed bumps. Apart from this issue it drives excellently and doesn't behave like there's slop anywhere.
Personally, I still think there's an issue around the top mounts, but can't see any problem when I check. I have seen the saloon and estate models have different types.. what's the difference?
Another option is play in the steering rack, but I can't see that causing this particular noise.
The car is a 2005 1.9 130 tdi sport estate.
Has anyone else had anything similar with their Passat? Or have any other ideas?




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