Yesterday, I had a rattle coming from what I thought was my idler pulley. I found the rattle and addressed it, but found myself cleaning the engine bay of all the grease/dirt that has built up over the few years I've owned my M. After I degreased the area around the belt tensioner idler pulley a bit, I found that the top mount that holds the pulley assembly to the front case of the engine was extensively cracked. I tried to get a good picture of the cracks, but the lighting isn't perfect. You can see on the mount two prominent cracks. There are two more on the left side (drowned out by the light), and one more that I can feel on the bottom of the mount. The picture doesn't exactly do it justice, but one of the cracks run maybe a half-inch up the crank case and almost all the way down the mount towards the head of the bolt. The red arrows are the ends of the cracks that are relatively visible from this angle.
Anyway, looks like stress-fractures to me, and I can't figure out if someone changed the pulley and over-torqued the bolt or if there is too much tension on the belt or what... The tension marks are aligned correctly as you can see on the right side of the picture with the blue arrow, but what do you guys think, is this something I should be worried about? Anyone else have this on their M?
FYI, I've got a 2003 Y34, 155,000 miles.
Thanks guys!
