I recently purchased a set I coilovers from you guys. I've been having some knocking issue's coming from the rear. I have checked the pillow mount, impacted them, and have fully disassembled/ reassembled them. I've been working on s13's for years an usually know what to look for. After the initial install I was happy. Smooth ride. Setup was nice. I took it out sliding one time and ever since I've had the knocking issue. I've gone through a process of elimination checking all the rear bushings, end links, subframe, diff, exhaust hangers, etc. everything is still good. The only reason i'm thinking it's the coil is because I've switched sides on the rears and the noise moved from driverside to passenger. Like I said I've impacted the top nut on the pillow ball mount. Fairly simple design so I know it's tight. Weird thing is, is that it sounds identical to a pillow ball strut top being loose. Any suggestions? I don't think the shock could be blown after a few switch backs. I tore them down and there isn't any leaks and it seems to have compression. I'm super frustrated.
Normally in the noise department, its something rubber on the car that is being transmitted through the solid jointed aftermarket parts usually the subframe bushing that you cant see a problem with unless you drop the subframe (Im not sure what method you used to eliminate the rubber parts) but they are the most common noise makers that OEM suspension wont transmit.
Right its not such a complicated setup so if you have totally narrowed it down to the damper and you are positive its that, then you can exchange it. However we have never had a noisy damper. Also never had a noisy pillowball. So replacing the least common noisemakers (also the most commonly blamed parts) may not be useful when its probably something else.
Thinking creatively, If there was noise coming from the coilovers because of some manufacturing defect it would likely be something else, like the things made with less precision than the bearing and damper.
The parts that are machined with some more +/- tolerance would be the bearing bottom spacer, the top nut, and the bearing housing with cover retained by 4 screws or lock ring from the bottom. Probably the best way to check these parts (if you are willing) is to jack up the car, remove the spring and work the bearing manually without the bottom mounting bracket attached.
Or send in the assembly for the noisy corner for us to check and we will replace the at fault part.