05 ML500 w rapid metallic rattling-banging on highway *solved*
 

Hey all- wanted to post this here in case anyone else ever has a similar set of symptoms. Wife drove 1/2 way across country in the ML, and on the way back, started getting a loud, speed-dependent rattling or tapping or banging sound that she thought was coming from the passenger side front. She called me and I was thinking it was a a tire separation or wheel bearing going, but she braked and pulled over and the noise would stop as she decelerated. It was really hard to pin down because it was intermittent and I was having a very difficult time understanding what she was talking about. She also had no vibration or pull in the steering and it was only at higher speeds at first, but got louder and started happening at lower speeds.

I searched all through this site and found reference to the carrier bearing, U-joints, wheel bearing, and then a similar sounding situation and a reply about the ebrake in this post:

http://www.peachparts.com/shopforum/ml-gl-g-wagen-r-class-unimog-sprinter/354518-sounded-if-my-rr-tire-had-exploded-but-hadnt.html

I had her pull over and met her at the nearest large-ish town and drove down to meet her and we got a room. The next morning, I had her drive the ML around in circles while I jogged behind and listened- and found that there was a click or scraping sound, then a metallic bang of metal against metal coming from the driver's side rear. It was speed dependent, and didn't start until we had driven for a while on the way to the shop we found on the IATN link Roy posted for us.

So fast forwarding here- we limped the ML at 20 to 30 mph to the shop and they test drove it but I guess they only got wear sensor-type noise, no bang, so they recommended rear brake overhaul. They said there was no play in the carrier bearing and the wheel brearings and u joints seemed ok. So, we approved the brake job. Then twenty minutes later, they called back and said they found the source of the banging noise- the parking brake on the driver's side had come apart, and the lining was making enough contact that when it heated up, would catch or bind and then pop in there.

They said that at some point someone probably drove with the parking brake on, and it got hot and separated- and had started to come apart but took a good long drive to heat up and come apart. They also mentioned that someone may not have adjusted it properly when they installed it- and it did the same thing. We explained that the parking brake light wasn't on on the dash, and the wife was absolutely adamant that she hadn't used the emergency brake (and didn't even know where it was) so they said it may have happened a long time ago- and after the PO drove with the ebrake on for 20 miles or something- disengaged it, but it probably had already heated up and started to seize or the lining had started to separate.

So. It got fixed- and cost a vacay day from work for both of us, a hotel room, two meals and $800 in parts and labor to do the rear brakes and parking / emergency brake(s)... But now there are no more weird noises and it stops "on a dime." Cheers- J