Motor mount bolts broken off in the block...

[joe_peters]

Bringing up a old trhead here but Last sun i was out on a trail and had my drivers side mount fail all 3 bolts sheard rite off at the face of the block... didnt crack the block thank god! so i sat there pondering to my self and then i got the idea of getting my die grinder and notching them for a flat head and bingo out no problem at all. came on here and searched and here is this thread! dam shoulda looked first! luckly i have a good size of lift and installing new hardware will be easy since i can get a socket up in there! wooohooo i thought i was F'ed:laugh3:

Planning to upgrade that mount bracket or just use new hardware?

Brown Dog makes a better bracket with seven mounting points for the driver's side and four on the passenger's side. They are sponsors and I believe give a discount to user/members with paid memberships.

 

[WrenchMonkey]

Brown Dog makes a better bracket...

This one? http://browndogindustries.com/su2572-0RXsuperkitwmotormountsandenginebrackets.aspx

It does look seriously beefy, and I really hate to dis a sponsor, but I don't think I could justify a $310 solution to a $10 problem.

But yeah, serious beef.

Robert

 

[FlexdXJ]

This one? http://browndogindustries.com/su2572-0RXsuperkitwmotormountsandenginebrackets.aspx

It does look seriously beefy, and I really hate to dis a sponsor, but I don't think I could justify a $310 solution to a $10 problem.

But yeah, serious beef.

Robert

Mental note taken! Those brown dogs sure are pretty but I agree, they are EXPENSIVE! Good thing I am handy with a dremel!

 

[joe_peters]

Well, the $310 includes their motor mounts, which you don't have to use (I believe).

Also, they are great people to deal with, so maybe they might sell you driver's side bracket by itself--the driver's side being the more problematic one. Give them a call, couldn't hurt.

BTW, their mounts run $75~$100, so the brackets would be costing you $210~$235, and that makes the price of beef a little more palatable (get it--palatable/beef?)

 

[old_man]

Squirt some ATF mixed with acetone up there to penetrate and loosen before you do any of these ideas.

 

[DesertRunner]

Bringing up a old trhead here but Last sun i was out on a trail and had my drivers side mount fail all 3 bolts sheard rite off at the face of the block... didnt crack the block thank god! so i sat there pondering to my self and then i got the idea of getting my die grinder and notching them for a flat head and bingo out no problem at all. came on here and searched and here is this thread! dam shoulda looked first! luckly i have a good size of lift and installing new hardware will be easy since i can get a socket up in there! wooohooo i thought i was F'ed:laugh3:

that happened on the pass side a few years ago leaving a parking lot!

 

[old_man]

As it turns out the bolts the factory used were just a few thousandths too long and would bottom out in the hole and not hold the plate solidly. As a preventative measure, I would back the bolts out, grind them down a bit, then reinstall and torque them.

 

[DesertRunner]

now that makes sense! could just add a washer?

 

[old_man]

Yes, lock washer.

 

[EndlessMtnFab]

I recall a conversation with Tim @ BrownDog and we were talking about the issue with the bolts.


From what I remember and what I've also read ... the bolts are too short (not too long) from the factory. Without enough thread engagement, they tend to back off a bit. Then with the wiggle room described a few posts ago .... the head snaps off.


Chasing the threads with a bottoming tap is a good idea too.




Joe

 

[1988 Cherokoo]

Sorry about that, I had mine broken on a yj and had to get a mechanic to do the work. I tried to do it at a DIY garage, but couldnt do it.

 

[89xjJe3per]

Anyone know the exact size of the 3 bolt's? I beleave one is shorter than the other? anyone?

 

[joe_peters]

Anyone know the exact size of the 3 bolt's? I beleave one is shorter than the other? anyone?

Per 87-90 Parts Catalog:

J400 7585 1 1.00"
J400 7622 5 1.12"

Don't have any other info than the lengths above.

 

[WrenchMonkey]

Anyone know the exact size of the 3 bolt's? I beleave one is shorter than the other? anyone?

I just went to lowes on my luch break. (6) Grade 8, 3/8-16x1 1/4" bolts, for about $3.25 total...

They don't have the cool flared head like the factory, but with a 5/16 washer, I think they'll be fine...

:wave:

Robert

 

[jimmy96xj]

Had this happen 2 me today on the passenger side how do u fit a drill in there to use an extractor or do I have to Yank the motor

 

[8Mud]

Had this happen 2 me today on the passenger side how do u fit a drill in there to use an extractor or do I have to Yank the motor

I'll let you know tomorrow night. I've been oiling mine down for a day now, I've got some good spray that actually eats rust. I'm going to try a Dremel and making a slot then using a low profile screwdriver or a right angle screw driver to back out the rest of the broken bolt. I may put the rest of the bolt through a few heat, spray oil cycles to break up as much rust as possible. Heat, then cold from the spray oil, then heat again 3-5 times, works pretty good on most stuff. I often use a heat gun instead of a flame, it usually works as well as the torch does and easier to control.

I've been looking and trying to see what will hit first if try to pull the motor down a little (ratchet strap?) and my son came up with the idea to jack up only the passengers side frame rail a little (actually a pretty good idea I was surprised LOL).

The expansion bulb on my A/C line looks to be the first thing to hit if the motor is tilted down anymore. If down doesn't work maybe I'll try up, I have a big floor jack. It is going to be tight and iffy.

I may just pull the motor, it isn't that big a deal, I have a decent engine hoist. But it is a pain and the chances of screwing something up is fairly high.

I have a right angel attachment for a hand drill and small Matika battery powered drill. A good sharp drill bit (maybe cut down and shortened). Slow speed and lots of oil works well. The battery drills are nice because you can control the torque better and have less chance of snapping a drill bit. I have a set of easy outs, but I'm not a big fan of them and have had poor results. I'm pretty good at sharpening my own drill bits, I've had lots of practice.

I've had better results using progressively larger drill bits until I just skin the threads and use punches and needle nose pliers to work the left overs out of the hole.

I'm going to give it a shot before I pull the motor, I have my doubts about the top bolt though. My guess is knowing when to stop, before you FUBAR it, then take the motor out and do it right.

Hope for the best and plan for the worst.

 

[WrenchMonkey]

Had this happen 2 me today on the passenger side how do u fit a drill in there to use an extractor or do I have to Yank the motor

Did you read the thread? Posts 7, 8, and 13 are your friends.

I would definitely suggest that method first!


Really funny coincidence. Just yesterday were on that same hill, and I told my passenger, "Hey, I busted a motor mount right here, like five years ago!"

And this morning, the thread resurfaces!

Nice searching, by the way...

Robert

 

[5-90]

So how do I fix this?

All three of my driver side motor mount bolts have broken off inside the block. One is sticking out about 1/4", the other two broke flush.

As-is, there's no way I can hammer and punch to em, much less a drill.

Does anyone know if I can pull the intake and exhaust manifolds, and swing the engine up enough to get at the bolts?

Or am I looking at pulling the engine? :bawl:

Robert

Known issue - as I've said before, EVERYONE should take a leaf gage set, use the smallest, and see if you can reach the shank of the screw. If you can, replace the screw and put a flat washer or two under the head (the problem is that the blind holes may not be deep enough for the screws, and the screw "bottoms out" and torques against the bottom of the hole. This prevents proper tensile preload in the screw, which leads to premature failure/rupture.)

If you remove the brackets entirely, you can probably push the engine up far enough (floor jack with a wood 'spreader' so you don't go through the oil sump) to get an angle drill in there easily - center-drill, drill out, then extract. Verify that the threads are still clean, flat washers underhead as above on the replacement screw (one is probably enough, two would be better.)

Check all other screws, replace PRN. If a screw head does not touch the mount bracket, do not reuse it! Replace it outright, flat washers, &c &c.

LocTite on the screws (#242 or equivalent) should be considered mandatory - just as on starter motor screws, bellhousing screws, &c &c.

EVERYONE check your engine mount bracket screws at your next opportunity! I'm not sure what years this is most prevalent on, but it seems to be scattered enough that everyone should do it anyhow.

 

[foolforfish]

Had this happen 2 me today on the passenger side how do u fit a drill in there to use an extractor or do I have to Yank the motor

Did this about a year ago. Used the Dremel on 2 of them to make a slot, used a slotted driver tip fitted to my rachet and bingo they came right out. But being an xj one had to be a bitch. Pneumatic right angle drill and bit and an easyout. PIA but it worked. Good luck.

 

[8Mud]

The rust spray my son showed up with was good stuff. Got all three broken off bolts out with a right angle drill and an easy out. Two came out easy, the top one was rusted in there pretty good. We actually drilled all the way through the center of the top bolt, sprayed oil behind the broken off piece of bolt and let it sit overnight.

All three were broken off between 1/8" and 3/16" below flush, there was nothing sticking out of the hole. I used a 1/4" flare fitting mounted to a piece of flat stock, through a hole drilled in it, a cut off flare nut to cinch it down and made a drill guide out of it. Worked great, we were within a 1/32" of center on all three tries.

I'm really glad I didn't have to pull the motor.:clap:

Next project is the new exhaust manifold and trying to get that back stud out that is broken off.

A near as I can figure all three holes are threaded to 7/8", the motor mount is 1/2" thick. I have three grade 8 bolts trimmed to 1 1/4" and hardened washers.

I took a stock bolt out of a spare motor (87) and it was 1" long.