I am in the process of replacing my crank pulley after the OEM one failed and separated. Old one removed, replaced crank seal while I am there, seated new lightweight pulley in place and started tightening it in place with a longer than stock bolt and then once I thought I had it far enough I started using the new bolt to tighten the pulley into place. It turned out that I really didn't have it on enough and only a few of the threads caught, which lead to me stripping the bolt and possibly damaging the crank threads.
Any advice on where to go from here? Of all the threads to strip, I may have found the worst one.


Striped threads going inting crank...

 

With only 2-3 threads trashed,
there is probably enough thread
further back to work ok IF you
use a tap to clean up the first
bit of the threads, blow out the
debris, and use a new bolt with
threadlocker (maybe Red Loctite
in this situation).

 

You really only want to do this once (if it works). May I suggest that you not use a lightweight crank pulley? (do a search for the horror stories) Use a ATI or PRW and do it right.

 

+1, I 100% agree with this.

As for the crank threads - Clean up what's left of them with a tap as cristo recommends. When installing the new pulley, don't use bolts. Get a piece of threaded rod and screw it into the crank as far as possible. Dry fit the pulley and install a couple of washer and a nut on the threaded rod. Tighten the nut to draw the pulley onto the crank. Remove the threaded rod and install the correct bolt. Doing it this way puts much less stress on the threads in the crank and you won't risk stripping them.

 

I'd be leery of using just plain old threaded rod as chances are it does not have the proper fastener rating -- probably Grade 8 here in the US -- as the crankshaft pulley bolt.

Here one can look at the bolt head and know the bolt grade. The number of radial lines -- plus 3 -- is the code. Thus a grade 8 bolt would have 5 radial lines on the bolt head.

Now it could be the factory bolt is not marked with a grade marking. The factory bolt is made with the proper grade of high strength steel, is rolled (to improve strength), and because it comes with an official MINI/BMW part # that suffices.

 

Yes - I did it this way ^^^ when installing my PRW. I had a hard time getting the new PRW pulley to seat flush/all the way and ended up stripping a few threads. I had a tap and die set on hand and chased the threads. However instead of using a threaded rod; I used a couple of stainless steel bolts (M12x1.75 thread pitch x100mm and an M12x1.75 tp x90mm) I'd purchased beforehand; I stacked up the different length "installation bolts" with several washers, used antiseiz and backing out the bolt removing washers incrementally. I kept an eye on the gap between the pulley and block while tightening the bolt. 2wo hours later = success. The pulley was finally properly seated and in-line with the other corresponding pulleys. I chased and flushed out any remaining antiseize from the threaded end of the crankshaft with degreaser and carb/brake cleaner before gingerly "hammering" in the new crank bolt with an impact wrench (84# if you can get a torque wrench in there).

But yeah - as mentioned above; have a tap and die set on hand.
Good luck!

 

Thanks for the feedback. I was using multiple bolts to pull the pulley in, but I underestimated how far it was on and should have kept going with the longer bolts first. Tap on order to clean out the threads and then either try again, with much more patience, with the longer bolts or look into getting a threaded rod (Grainger sells them in M12x1.75 in hardended steel class 12 or 8.8, which I guess is what would be needed?) and tighening it down with a nut and washer.

I did do a fair bit of reading about solid vs. OEM vs. liquid filled pullies, and figured that for me as a weekend driver on country roads, I wouldn't be pushing the hardware to breaking, but might get a bit extra responsivness. I may regret the decision, but hindsight is always 20/20.

 

Well - Don't feel too bad about your decision on the crank pulley. Everyone has an opinion.
I'd later learned or heard from others (as in my case), that the PRW can be a nightmare to install. It was.
After all that said and done - I have absolutely no regrets regardless.

 

I made the mistake of not installing the tool fully when drawing the new pulley on and completely stripped out my crank thread.
As i am a machinist i weighed up my options and deemed it safer to retap it to a size up. using what i believe to m14 x 1.5 which i had turned down to the oem length as the old one. i even made a long one for drawing on the pulley if i ever had to again, which i did when my pulley split in two.
I feel like this is the best way to approach this even though it took me two hours of slow tapping to complete this.

 

Quick follow up post.

I pulled the pulley off, cleaned up the threads with M12 tap, cleaned it all out with some brake cleaner and air to get any bits out, and then mounted the pulley (first heating it in the oven to expand the metal) by slowly pulling it in with a series of M12 bolts and washers. Patience payed off.

Just need to get to the rest of the jobs now (O2 sensor, strut mount replacement, front bushings, etc.).

Thanks.