engaging the parking brake - creak

[rh71]

Originally Posted by FunfDreisig

One of the quirks of our late lamented 2001 X5 was the loud creak/snap when going over bumps at low speed. After BMW technicians replaced nearly all of the front suspension bits in multiple failed attempts to eliminate this creak/snap, I took off the sway bar during a BMW CCA tech session at the local dealer and discovered/fixed the noise The problem was grit build up in the rubber mount/bushing that would freeze and quickly release the energy/sound to the large aluminum 'splash pan' under the engine. This flat pan acted like a large speaker amplifying the sound.

The diagnostic clue was that the creak/snap noise only happened when the two front wheels went over a bump at different times (i.e. driving over a speed bump at an angle) at low enough speeds to get the two sides to react differently.

Funf Dreisg

That sounds pretty accurate to what I'm getting as I turn one direction coming off the driveway lip... wheels coming off at different times. I've heard it in the back wheels too. You say it's a grit build-up... is this bad for the whole system over time? You also mention it freezes but we're having summer days here. It is not happening as frequently, but it is still happening. Also wondering why there would be grit build-up in a relatively new vehicle - been happening since near the beginning. Regardless, I'm hoping that's the problem and that it is not serious.

[FunfDreisig]

Originally Posted by rh71

That sounds pretty accurate to what I'm getting as I turn one direction coming off the driveway lip... wheels coming off at different times. I've heard it in the back wheels too. You say it's a grit build-up... is this bad for the whole system over time? You also mention it freezes but we're having summer days here. It is not happening as frequently, but it is still happening. Also wondering why there would be grit build-up in a relatively new vehicle - been happening since near the beginning. Regardless, I'm hoping that's the problem and that it is not serious.

Sorry my terms were meant to be descriptive not literal. By "freezes' I meant that the rubber mount/bushing 'sticks' to the sway bar as it twists. Then 'unsticks' letting go of the bar quickly which lets the mount relax back into its normal position with a snap. This mount is attached to the large aluminum plate under the engine. The key is the location of the mount to the aluminum plate which acts as a amplifier of relatively quite sounds.

In my case the inside of the rubber mounts/bushings for the sway bar were very dirty and had built up gritty/rusty bumps on the sway bar. I had to scrap the grit/rust off the sway bar with a utility knife. The grit stuck to the bar made it very rough. So it did not twist inside the mount smoothly. This same behavior could be caused by anything that keeps the sway bar from being able to twist smoothly inside the rubber mounts (e.g. being too dry, too tight, etc.)

Of course the dealer didn't have the new mounts in stock when I was at the tech session. So I simply scrapped the grit/rust off the bar, liberally lubed the mounts and re-installed the bar/mounts. The noise went away completely. We later had new rubber mounts installed. If you are even halfway good with a wrench, you can pull the mounts and check for grit/rust build up and spray the inside of the rubber mount with a small amount of rubber lube. You don't want too much lube because it might attract more dirt.

Funf Dreisig