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DIY: Do It Yourself
Post here to share or improve your wrench turning skills! All BMW E46 DIY tips, tales, and projects discussed inside. Learn to work on your car and know the right BMW parts you will need!

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Old 12-03-2015, 05:51 PM   #1
Registered User
Join Date: May 2014
Location: mass
Posts: 318
My Ride: 323i
Sheared rear subframe bolt...

About a year ago i did a rear subframe reenforcment, the driverside rear attachment of the rear subframe had failed(common in the first year of e46s especially the 5spds like mine), the steel block the bolt screws into underneath the trunk sheet metal popped it's welds and sheet metal below this block(sheet metal you can see from below car with rear subframe removed) had cracked

It took to the repair fine gouged out cracks drilled ends to stop spread filled with weld and ground flush then rewelded steel block recieving the bolt in place and added reenforcement plates worked great

I noticed today when doing some work on it and inspecting rear it looked like the bolt was a mm lower than it should be was not contacting bushing(i had lifted rear from diferential so subframe was pushed up against unibody not hanging on bolts) and went to tighten it

It was a bit loose and just when i was about to leave it it sheared(my fault i know fml) prob at about 120 ft lbs much lower than i would have expected

It is bolt #5 from the rear subframe diagram in the subframe reenforcement diy guide(will edit it with link in a min am on phone)

Im pretty screwed lesson is obv to use the proper torque wrench and check torque spec but is too late for that now

It obv cant drive very far without severe risk of damaging other three atachments of rear subframe so need to deal with it immediately

I dont think a bolt extractor will work, those bolts are some of the highest torqued on the car and would presume at least 120ftlbs if not more to pull it out but my experience with extractors is limited. The block is meaty enough to drill a size larger and tap it but may have to drill metal insert of bushing larger if i did that, and if yea would be 5-6inch of steel to drill not something im looking forward too. I swore i wouldnt try drilling that extent again after drilling through the base of posts on exhaust line to put bolts there(cm of steel)

Any advice? Dropping subframe would be huge pita as im pretty sure the steel recieving block of one of the front bolts popped its welds when putting it back last time as it started spinning in place jusy shy of its torque spec (wtf bmw?) But could cut it and replace if i need to drop it, if theres a tap long enough can drill through metal bushing insert a size higher with it still there and then into sheared bolt, drill another size up on bushing so bushing doesnt get threaded and then if can find a tap long enough tap the ould drilled out bolt area? Can an air drill with right bits accomplish this the old exhaust posts was most ive drilled and that sucked, this would be more difficult i think...

Cars worth 1500 i might just part it out but sounds silly to do that over a bolt
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