OK here's the story. My brother hit an enormous pothole and the motor mount bolts on the passenger side of his (Mine actually) XJ completely ripped out so now the only thing holding the right side of the engine up is the bottom of the distributor housing is sitting on the part of the motor mount that is still attached to the side wall. (Update. I jacked up the motor a bit and wedged some thick rubber between the mount and the slanted bottom of the distributor housing to make clearance for the cooling fan) I took a quick photo of the broken mount to show the problems I have: (Continue reading below photo)



The hole in the green square only goes in 1/4" then there is a snapped off bolt in it. The hole in the yellow square is empty but the threads are stripped. The main problem is the one in the red which sticks out has the whole backside of it snapped off as far in as the bolt goes.

My main question is: How thick is the metal on the block where the bolt hole in the red box extends out? Could I grind it down past where the busted area is then drill and tap it? I'd have to make up the difference with washers or something. Is there an alternative way to support the motor without using these holes? His XJ is on it's last legs so I just want to do the minimum to make this daily drive able until he saves enough for a replacement.

 

Idk how much this will help, but I know that brown dog makes engine side mounts that grab more than the factory three holes. Maybe you could get one or two of the holes back and then add the brown dog bracket that I believe grabs 5. You'd have 4 bolts grabbing it then.

 

You're gonna have to tap the three remaining for a larger bolt......yeah, the the BD mount brackets.


Oh, and never let your brother drive your jeep again.

 

Brown Dog & brotherly ban x2

 

Wow. Post up some after pics when you get it fixed.

 

X2 on the brown dog brackets

 

Yep just repair it, it was a ticking time bomb as soon as it left the factory, just happened to be your lucky day. Make sure the drivers side bolts are not bottomed out as well.

 

Here's why it happens:

From Jon Kelley aka 5-90 @ www.kelleyswip.com



This is a known issue.

1) Unless you're going to get silly with the skinny pedal, 2xSAE8 screws on one side won't be a huge problem. You'd be better off with three, but if you don't get silly you'll be okeh.

2) The Brown Dog engine mounts use two or three additional holes on each side, and spread the mount/clamping force over more of the block. This is invariably a good idea, and I'll probably be doing it as I refit my 88.

3) The primary reason that the screws snap is because, sometimes, the screw holes in the block aren't drilled & tapped deeply enough. This causes the screw to bottom out in the hole, so you end up torquing against the bottom of the hole instead of stretching the screw (as you're supposed to do. Not your fault - you aren't doing anything wrong.) The screw is not stretched properly, and the head is not butted up against the bracket, so there's some room to move there. Vibration then causes wear cycles on the screw, which generally leads to rupture.

The easy/cheap fix? When you replace the screws (3/8"-16x1.25", as I recall,) put two flat washers under the head before you screw it into the hole.

The check? Take a feeler gage (.003" to .005") and try to slide it under the head of the screw. You'll be able to get under the corners (look at the hex head, and you'll see that the surfaces curve toward each other slightly) if it's a standard hex head - if it's a flanged hex head, you should not be able to get under the head anywhere. If you can slip the gage under the head, you have a problem. If you can touch the shank of the screw, you have a big problem!

In no case should you reuse the screws after you take them out - they'll be stressed under the head, and you'll have a significant reduction in strength. Replace them outright, putting washers under the head as I mentioned before. The washers will make up for the slight lack of depth in the hole (two of them will be about 0.125" or so,) and allow the screw to be preloaded properly.

 

Good advice.
Does everyone think it broke off due to the bolts being loose?

 

I feel you man I just bought this low mileage 99 complete engine not easy to find as you know....Nothing almost $400 didn't fix with the Brown Dog setup.

 

Bolts sheared off because of the fact they are too long and are bottomed out in the threads in the engine block.

 

I do.

 

Thanks for all the input. I looked at the Brown Dog mounts and they were a bit pricey. Don't plan to keep this XJ much longer. (By the way the website said the passenger side one uses 8 contact points) I'm hoping to salvage 2 of the 3 holes and have enough contact and strength (Maybe red LocTite?) to get a few more months of daily driving use out of it.

The bolt hole in the yellow square of my original photo is the best one and just needs to be tapped out. The hole in the one with the red square around it goes in a ways and the busted off chunk only accounts for half of the depth. I was thinking of grinding it down past the broken area and then using a shorter bolt and some washers so I'd at least get a half bolts worth of bite.