turbolizard 38 Report post Posted December 9, 2015 I am taking apart a front suspension strut on an e34 BMW and things are weird – I have done many struts before and never seen one behave like this. My normal process is… loosen the strut top nut slightly, while still in the car (which I did) take the strut assembly from the car (which I did) compress the spring, which relieves tension on the top mount remove top mount and disassemble the spring and strut. Not this time though – at step 3 the shock damper rod is pulling into the body of the shock as the spring is compressed, keeping a high compressive load on the spring. The rod pulled in about 40mm. The force pulling the rod into the shock body is really high – it is not just dropping under gravity. Even with the spring very compressed you cannot pull the top mount back up by hand at all. This behaviour was totally mystifying me so to confirm it I put a piece of metal angle up against the piston rod, between the shock body and top mount, to prevent the rod from moving down into the body. I could then compress the spring as I expected and could easily get it loose between the top mount and bottom perch (with the metal angle holding the rod at full extension). This confirmed that the piston rod is pulling in pretty hard. With the spring compressed and loose there is now a lot of compression force on the angle (piston rod is definitely pulling hard into the body), so there is still tension on the nut. I do not want to release the nut off the top, even though the spring is no longer pushing on the top mount. If I did release the nut then I expect the rod would shoot downwards. I don’t think things would fly anywhere because there is no elastic energy in the angle holding it up, but I don’t want to do it when I don’t understand the cause. What the heck is going on? The replacement struts I have push outwards with gas pressure as expected. Quote Share this post Link to post Share on other sites
aja540i 1895 Report post Posted December 9, 2015 The old struts on my e39 did that when i pulled them out, there was still some gas pressure acting on the top side of the piston, and they both retracted into the shock body. Mine werent as bad as yours, i could pull them out by hand, but as soon as i let them go they went back in even if i held the strut upside down. Quote Share this post Link to post Share on other sites
turbolizard 38 Report post Posted December 11, 2015 Thanks - I think it was gas pressure acting on one side of the piston. I'm not sure how that occurs internally, but it did feel like that. I put a piece of rubber sheet around the base of the piston rod and pulled it really tightly in place with cable ties. This created a lot of drag as I released the nut and it all moved slowly enough to be totally controlled. New shocks now installed with no hitches. Quote Share this post Link to post Share on other sites
