need to tap a motormount support arm.. - PeachParts Mercedes-Benz Forum

coadman · #1 06-19-2007, 08:09 PM

I finally got my motor mount bolts to replace my motor mounts on my 1979 240D(with a 1980 motor). The bottom bolts must have vibrated out or the PO forgot to put them in!? Anyway, we tried to install one of them this afternoon, and after pushing.shoving the motor around, finally got the holes lined up. But, try as I might I could not get the bolt to start, at least not the best, so we removed the support arm that the bolt screws into, as I suspected the threads were stripped. My suspicions were correct, as the thread was messed up for the first 3-4 threads, then good down below. Might have been the reason the bolts had fell out, as they were not properly installed the first time? So, does anybody know what size tap I need to fix the threads on this? The bolt takes an 8mm allen wrench. I have access to some metric tools at my local JD shop, but need to know what I am looking for.
thanks,
Jim

murdockspencer · #2 06-19-2007, 08:46 PM

take the bolt with you to get the tap tool and you can match it right up. If the threads are too stripped, you might consider getting a thread repair kit with the steel thread inserts. This would probably last longer than aluminum threads cut fresh. If I remember corectly the hole you want to tap is into cast aluminum. But if your threads aren't that buggered, just a tap should do.

coadman · #3 06-19-2007, 09:15 PM

Quote:

Originally Posted by murdockspencer

take the bolt with you to get the tap tool and you can match it right up. If the threads are too stripped, you might consider getting a thread repair kit with the steel thread inserts. This would probably last longer than aluminum threads cut fresh. If I remember corectly the hole you want to tap is into cast aluminum. But if your threads aren't that buggered, just a tap should do.

Yep, it is cast aluminum, and it is only the first few threads(3-4) that are not good, the ones the rest of the way are good. Of course, I dont know how far the bolt screws down, as there were none when I took the mount a part. I used a helicoil kit on a stripped out thread going from my driveshaft to my motor on my JD sprayer last year, so I know how those work. I dont think I would need that for this job, hopefully.