Things broke...

[MR 325]

Was doing some work on the car today, changed the output shaft seal. selector seal, selector rod joint, guibo, transmission fluid, differential fluid, and modified my shifter to sit correctly (finally after over a year).

And THEN I discover something...

Three out of four of the driver side engine mounting arm bolts are broken! Sheered off in the block. The fourth bolt is loosely hanging on to the block still, unharmed. What the fuck happened! My friend/boss is helping my fix it tomorrow but wtf mate, seriously. Anybody ever seen this? It's not like I have some high horsepower beast here.

[318isbmw]

Glad you noticed that. My only guess is the bolts weren't good ones, and since the 4th was loose put more pressure on them and sheered them off? Seems like a stretch, but never know. Other than that, I got no idea, just get all new and torque em all down is what I'd do.

[matt325is]

What was the torque on the bolts? If bolted too tight (arm torque wrench style), it may have plastically deformed the bolts (instead of elastic at a lower torque). Definitely could have weakened the bolt causing them to shear. Or maybe just a bad batch of bolts.

matt

[MR 325]

I'm sure I just tightened them with a 3/8 ratchet.

[gazellebeigem3]

are/were they graded bolts?

[jahnaboi]

Lol damn matt, your what? Pushing 1000hp with your n/a s50? LOL! Jk. Wow. Luckily you didn't drive the damn thing to the point where it fell and your oil pan would have to sit on your subframe and crack and save the rest of your motor...!!!

[e30this]

I had this happen. Lost 2 out of 4 on the passenger side.
I dont know why it happend but it did.
Was all of your bolts OEM or just off the shelf?

I was lucky enough that when they broke it was just the heads of the bolts so I was able to get them out with vise grips.

[jahnaboi]

This possibly could have happened if you torqued the motor mounts with the engine weight on them... possibly thinking that they were tight but were tight at all... so ahead you gave it a little more torque weakening the metal itself? Iono, just throwing out ideas.

[Tree18is]

shifting like a fuckn beast wouldnt do it right?

[MR 325]

I think they were actually brand new OEM bolts, if I remember right.

I'll put it back together tomorrow and hope it's good, lol.

[MR 325]

shifting like a fuckn beast wouldnt do it right?

Haha, no way!

[MIKe30]

I think they were actually brand new OEM bolts, if I remember right.

I'll put it back together tomorrow and hope it's good, lol.

There's got to be a reason it happened, and to more than one person. That idea of perhaps having put them on with the weight of the motor on it sounds like it would do it to me. If you just put new ones on the same way you did the old ones, it's bound to happen again.

[madjurgen]

This is a very common issue with the MZ4s. To the point that all new owners are switching out the new BMW bolts for 10.8 grade bolts from McMaster or somewhere similar.

[MR 325]

There's got to be a reason it happened, and to more than one person. That idea of perhaps having put them on with the weight of the motor on it sounds like it would do it to me. If you just put new ones on the same way you did the old ones, it's bound to happen again.

Well when the arm was first put on it wasn't even in the car! When I put it back together yesterday, I had the car on the hoise and took the weight off the engine with a transmission jack.

[BeirBrennerE30]

runs outside to check engine...