353casey

I HAVE A 94 XJ WITH A ROUGH COUNTRY LIFT.WAS DRIVING IT TODAY HEARD AN AWFUL SOUND COMING FROM THE FRONT DRIVE SHAFT FOUND OUT MY BOLTS SHEARED OFF MY DRIVERS SIDE MOTOR MOUNT AND LET THE MOTOR FALL ANY BODY MAKE A HEAVIER MOUNT

diskman

First of all there is NO NEED TO SHOUT. We hear you fine.

The original mounts work fine for everyday driving, BUT you need to check for rotted rubber in them. If the rubber is bad, replace the mounts.


The snapped off bolts are due to them loosening up over time and failing. You NEED to remove the broken bolt part from the block and replace with new Grade 8 bolts. Same on the other side of the engine.

It's a common problem I guess.

JeepingDan

bolts sheared off huh.. oh boy we have problems.

lil'whiteXJ

check these out

http://www.mountainoffroad.com/Catal.../XJmounts.html

JeepingDan

Now those are some sexy motor mounts.

353casey

Thanks for the advice

1989cherokee

Same thing happened to me last December but on the passenger side.

353casey

Changed mine out sunday with a new stock pair . Found out they had changed the motor and had the wrong bolts in the block they were to long the mount never tightened up

djlarroc

Reviving this thread...

I just learned today that the awful vibration from my xj (which I purchsed 1 week ago) is because the 3 pass side motor mount bolts are broken in the block.

I managed to drill the holes through the old bolts, but am not sure where to go from here. They are not perfectly straight holes, and I tried to re-thread the holes, but it's not working well. Do you guys think self tapping bolts will work?

Mendax13

guess ill revive this. i got a 95 xj 4.0 and dealing with some bad death wobble that lead to my motor mount bracket bolts shearing off. they were recently replaced with grade 8's and they broke. so i gotta fix it to drive it anywhere. any one know what the bolt size is for them?

wiggles

Look into brown dog engine mounts

cruiser54

THIS is why the bolts break:

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.

CCKen

Rather than messing around with hardware store bolts you can get new OM bolts from the dealer that are the proper length, strength, etc. All six are the same.

OEM # 6034989. MSRP $3.35 each. Less from some online Mopar sources.

cruiser54

Just remember to check them as the blocks weren't threaded deep enough. This started with teh HO engine bTW. Never seen it on a Renix.

CCKen

Agreed.

The ones I just removed from my '99 engine are dead nuts 1 1/8" long and fit tight against the mount. I think the mount thickness may play a roll in the bolts not going deep enough to fit tight against the mount.

Even the OEM bolts should be measured before installation.