XM suspension

William · Post by **William** » 22 Jun 2004, 21:32

I thought that the back end of my XM was getting a bit hard the other day so I got out and bounced it up and down for a bit. It was hard at first but after a couple of bounces it jumped up and hit me on the chin[B)]After that it felt about right. Why did it do that?
It can't really hear the names I call it....can it?

Post by **philhoward** » 23 Jun 2004, 05:09

Were you peforming "external citaerobics"??? lol
Perhaps all that bumping confused the height corrector..so it bit back!

DLM · Post by **DLM** » 23 Jun 2004, 15:31

Have you checked the rear arm "lean" on full height lately, or listened out for clanks or clicks from the rear end? As rear arm bearings and races wear or corrode they can actually impede rear suspension travel, particularly if they have literally got stuck in a "rut" cause by collapsing bearing cages or a cracked race. Well, that's my theory anyway.
Also, it could be that the bouncing freed up the mechanical height corrector linkage if that was starting to gum up and seize. Internal citaerobics called for, methinks.
Does this age of XM have any anti-sink spheres?

ItDontGo · Post by **ItDontGo** » 23 Jun 2004, 15:59

That sounds very like the valve for the soft sphere suddenly opened and unusually the sphere had high pressure in it.
The suspension ECU should equalize the pressure by frequently opening the valve for a short time. It does this for the very reason that, if it opens with a high pressure in it, the car will jump up. However as the default is stiff I dont see why it would just suddenly open and also why it would have high pressure unless there is a problem with the electrovalve. It might be a bit sticky but is that likely?