My X5 35D 3.0 Diesel from 2008 has started with a strange unhealthy sound when de-accelerating at low speed. It is random, some times it is there, sometimes it is not. Now it is mostly there all the time.
I hear a chunk/knock sound. I suspect it to be something related to either the rear diff, or rear breaks as the chunk/knock sound frequency is related to speed. So when coming down on speed, letting of the throttle or braking, the knock starts with decreasing frequency as speed is decreasing.
It is only when I let off the throttle, and at low speeds that the knocking is present. At least I don't hear it on the highway. When ever I hit/touches the throttle the chunk/knock goes away. Something is hitting a turning object somewhere...but I cannot tell what it is. I suspect the diff, but not sure
Does anyone have an idea what the knock issue could be? It is coming from rear end under the car, and not related to any loose parts in cabin, spare tire etc.
Thanks :-)
Get on a rack and inspect the rear suspension
Thanks, how is it you expect the suspension when the knock freq is linear to speed?
Yes, brakes changed by a mechanics shop - but the knock was randomly there before the brake change, just not that often. It was not detected during the brake change by the mechanics, properly because knock did not show up at that time of test drive before handover, and I did not comment on it before delivering the car. Now, one month after the brake job, the knock seems suddenly almost all the time (maybe 80-90% of every off-throttle slow downs on low speed), really strange. Before I thought it was some kind of stone sitting somewhere along the brake shields, but now I believe it must be something else. Noting to see when I look under the car...
Thanks a lot. I think the guibo flex disc is a candidate for the trouble and soon $garage visit. Found beneath picture on the web, if having some loose worn "dreadlocks" hanging loose when off torque, that could properly cause them hitting surroundings and hence make the knock sound. When engaging the throttle the loose ends might behave somewhat different and flatten out....guesswork, but could maybe be the case and source
Guibo.png
I will have a closer inspection on them tomorrow
Thanks
Why guess when a shop can inspect the under neath of the car, I have rarely replaced guibos in all the BMW's I've seen over the years, it I had a tech that was fixated on them every vehicle check he would list them as lots of cracks, I would go out and look and they would be fine, luckily he wasn't at the shop to long
Last edited by jclausen; 02-12-2020 at 09:08 AM.
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