Damaged crankshaft?

[dennisvab]

Hi folks. I've been a lurker, first time posting on this forum. I have a 2011 X5 with the N55 that I am repairing after a front end collision, vehicle is for myself.

I have no idea what the previous driver hit, but some of the impact was absorbed by the crankshaft (through the vibration damper/hub).

I initially replaced the damper, and noticed that there was still a "wooble". Here are some slo-mo videos

https://www.youtube.com/watch?v=lJ-QOgIt91M

https://www.youtube.com/watch?v=eaB8S1ZzKJc

So my next step was to replace the crankshaft hub. It is better now, but there is still a "wooble" present. It seems much improved however.

https://youtu.be/oKWO4XK_6yg

What I dont know is if there are going to be any negative consequences down the road if I do nothing else, and leave it as is to drive. My concern is that there is a slight deformation in the end of the crankshaft, and leaving it alone would cause additional stresses on the surfaces the crankshaft rides on.

[bfeng]

Any wobble in the crank. Will wear out your bearings faster. And the crank nose mat eventually fatigue and break off. Your bearings and bearing caps may already be damaged. Unless you are going to flip it, I'd have the crank replaced and the bearing carrier crack checked.

[ard]

Do you have a picture or link to the car showing the overall damage??

[dennisvab]

Originally Posted by ard

Do you have a picture or link to the car showing the overall damage??

Heres a link

https://goo.gl/photos/LpvF4i4xqeTC7Jbz5

[ard]

Im not sure you can simply think about 'what hit the parts from the front'

You need to consider that the engine was, most likely, being driven at power at the time of the accident. If the accident caused the front/exterior of the driveshaft to stop, the torque applied by the running motor could have damaged that crank.

There is a reason these are cheap...Auction? Where?

[absentmathis]

OP, wondering whatever came of this? The damper on my 4.8 has developed what appears to be a similar wobble, however it's never been wrecked per reports and history that I have. I have yet to remove the damper or hub to inspect, but I wasn't under the impression that these are typical wear parts.

[dennisvab]

Originally Posted by absentmathis

OP, wondering whatever came of this? The damper on my 4.8 has developed what appears to be a similar wobble, however it's never been wrecked per reports and history that I have. I have yet to remove the damper or hub to inspect, but I wasn't under the impression that these are typical wear parts.

I ended up replacing my engine with a used one from a 335i. I am tearing apart the old one, but your problem doesn’t seem to be as bad as mine. I’ve heard of the dampers starting to wooble but I would say that is due to age or mileage. I think your damper may have just gone bad.

[ard]

This is an oldie!

OP, be interested to see what you find/found. Pics, etc...

[AlpineX]

Originally Posted by absentmathis

OP, wondering whatever came of this? The damper on my 4.8 has developed what appears to be a similar wobble, however it's never been wrecked per reports and history that I have. I have yet to remove the damper or hub to inspect, but I wasn't under the impression that these are typical wear parts.

The damper is a wear item, not sure how common on that engine. The issue with the car from the OP is that during an accident, impact was made with the crankshaft (which is floating on oil inside the bearing tolerances). The inward impact likely or possibly damaged a thrust bearing and may have caused minor or major damage to the internal geometry of the engine (even more severe if [likely] while running as Ard mentioned). I think the OP did the right thing by putting in a used engine.