Engine mounts repeatedly breaking 2012 KW T700

My very first thought - followed by @x1Heavy ‘s idea.

 

I second the motion. Either that or driver is beating the piss out of truck. The proper size grade 8 bolt and mounts should last a very long time unless either one of the conditions is going on

 

I replaced my damper with a Pittsburgh power on my cat at 500k just for piece of mine. Used to get a rattle in front end and wouldn’t you know it, the old dampener was some how making that noise.

 

Even Grade 8 bolts aren't immune to snapping.

Back in 2001 I had a 99 Freightliner Century Class with a Detroit Series 60, the A/C compressor bracket bolts were constantly snapping and they were Grade 8 bolts.

I would replace them with Grade 8 bolts again and again, even using Loctite so they wouldn't come loose. It still didn't help, it got so bad i carried extra bolts with me because I knew they weren't going to last.

I found out that it was a common problem with Freightliner trucks and the A/C bracket bolts breaking all the time.

 

Grade 8 bolts will hold more... But shear easier. They are harder which also mkes them more brittle. Grade 5 hold only slightly less but are less likely to shear... They are softer which allows them to stretch somewhat. Thereby absorbing more shock and vibration before breaking.

 

Bottom line though. In the topic of motor mounts, you need to be using grade 8 bolts. They need to be torqued to much more than a grade 5 can hold. The motor mounts come with sleeves so the bolts are sleeved. Shouldn’t be any sheering going on whatsoever. It would need to cut through the mount and then the sleeve itself before it gets to the bolt. So bottom line, there’s an issue here if the bolts are sheering. If the bolts are braking and not destroying the mount itself, it’s becuase the bolts were overtorqued with impact gun or there is major operator abuse going on. If the bolts are sheering, then you have all kinds of alignment issues. If having alignment issues, I suspect loose bolts everywhere on the rest of the motor mounts and ssupports the mount to frame. Front to back. I would also suspect you have frame crossmember severely loose under the cab as well. Start checking for play in every single bolt

 

What about frame twisting?

 

I’ve used heat treated on my a/c bracket still snap. Might as well give grade 5 a try.

 

One got same problem with 01. 99 had bad alternator adjustment set up thought I was done which problems as this has a pad mount It’s a bad design that will be upgraded by me somehow still on drawing board.

 

Same problem here, 1995 freightliner detroit 60. The mounting holes become oval and the bolts break. The timing cover seems not strong enough to hold the alternator and ac pump long term. It seems like the only fix is a new timing cover. I eliminated this problem by eliminating the air conditioning. Its a short belt 2 pulley setup now, alternator only. Its way better if you dont need a/c.