[rocky]

https://flic.kr/p/WVFGfS

Any help is appreciated. This is the 6th time I'm doing this job. The bolts for the fan belt tensioner mount keep breaking. I'm out of ideas. I have replaced everything. I've tried different grade bolts and even studs. I think the problem is with the metal surface you can see breaking away at the 2 bolt holes. If that's the case it will require a new engine as it is part of the block and not a cover. Any ideas or advice? The fan hub turns freely and is working properly. That's all this belt runs.

[00SSHarrison]

I tried to find some info on this but there is no service bulletins or any real info on this prob.
I worked for Detroit Diesel for 8 year (they build the MBE 900 and 4000) and another 3 now for Freightliner, ive worked on a lot of MBE's and i cant ever recall having this prob.
As for a fix i don't think going to a bigger bolt is a good idea but maybe a threaded insert with some bearing retainer might work, also is there a locating dowel on your tensioner?

[rocky]

I tried to find some info on this but there is no service bulletins or any real info on this prob.
I worked for Detroit Diesel for 8 year (they build the MBE 900 and 4000) and another 3 now for Freightliner, ive worked on a lot of MBE's and i cant ever recall having this prob.
As for a fix i don't think going to a bigger bolt is a good idea but maybe a threaded insert with some bearing retainer might work, also is there a locating dowel on your tensioner?

Yeah no one else is having this problem. I have talked to Freightliner and Detroit Diesel as well. There is a dowel on the bracket put it just sits on the block. Unfortunately I had to go from a 10mm bolt to a helicoil and now I am using a 7/16 stud. I talked to a local bolt company (kind of like a Fastenal) and he was thinking the grade 8 hardware I was using may be too brittle. I never thought that would be an issue. I forget the grade of stud he gave me but it is supposed to be able to handle any vibration better than a grade 8. I do not now I am at the end of my knowledge on this one