uprated suspension creaking on one corner - e39 528

I replaced my standard springs with Eibach itmes on Sunday. It was all good driving home from my mate's house where we'd done the work on Sunday evening.
Noticed yesterday driving home from work that I had an annoying creaking / twanging sound coming from the rear passenger side.
With my hand on the spring as I was jacking the car off the ground, you could feel it sort of 'twanging' as it was being uncompressed.
I stripped out the rear seat, etc again last night and loosened & re-tightened the shock strut top nut - as well as spraying some WD40 up to the underside of the top mount area...but can't really get to it without dropping the entire shock out again.
Everything is tight.
When I took the car out, the twanging/creaking stopped for a few minutes after I'd been jacking the car up and down, compressing and uncompressing the spring whilst I was investigating last night. But came back again.
It seems to creak when the car is level and just travelling down your average, slightly bumpy British road.
It stops creaking if it's compressed (I did a few laps of a roundabout on the way to work this morning) or the weight is taken off the passenger side (ie: by taking a left hand corner...doesn't have to be taken particularly agressively either).
Any thoughts before I spend my Wednesday evening out in the cold & the dark stripping the thing down again?
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anyone got any thoughts at all?
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Russ (www.e36coupe.com) wrote:

My only thought was that maybe the rubber insulator for the spring perch is worn through (or forgotten)? Metal to metal contact at one end of the spring would give these symptoms...
--
-Fred W

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that's about as far as I go to be honest. The rubber seat is definitely on, as I put it back on!
Perhaps it's literally got damaged yesterday with the new springs on or something.
I'll have to have a look I guess.
I also thought it might be top mount related, but they looked fine when they came off and the car wasn't making any funny noises before I took it all apart on Sunday.
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Russ (www.e36coupe.com) wrote:

I think if you take the spring back out, you may find some "witness" marks that show you where the creaking may have originated. Look carefully. You'll find something.
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snip

How old is the vehicle?
Any accident damage?
Kerbed or driven over humps too fast?
Look for loose bits of chassis / bodywork.
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A mate gave me a hand this evening to strip it all down again.
Transpires that the rear spring wasn't seated properly so was rubbing on the inside of the metal cup of the top mount.
As it happens, I bought 2 new top mounts on the way home tonight, just incase, and seeing as we had it apart anyway, we replaced both sides. Fully lubed up, of course
Anyway, all's well and non-creaky in the e39 camp now.
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