WARNING: All 4.0 owners check your motor mount/block Bolts!!!! - Page 2 - JeepForum.com
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post #16 of 251 Old 09-25-2008, 10:43 PM
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If all bolts are ok, is it a good idea to replace all of them with grade 8 ones?????

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post #17 of 251 Old 09-26-2008, 03:17 AM
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1994 XJ Cherokee 
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been there also, ran over a railroad track pretty hard motor mount bolts broke. I did not know one of the bolts had already came out and was gone.
The other 2 broke off in the block. I drilled out the bolts and used an ease out to get them out. Also had to use alot of heat from a torch. Not a good day.
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post #18 of 251 Old 09-26-2008, 06:46 AM
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Where is a good place to get new mounts and bolts? Also what brand are those ez outs pictured?
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post #19 of 251 Old 09-26-2008, 09:27 AM
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Yes, I would like to know a little bit more about this as well. I have 220k on my motor and have never touched the motor mounts or bolts holding them in. Do you guys just go to the hardware store and get grade 8 stuff or is this a part that comes with aftermarket motor mounts? This is the first time I have heard about this problem, and I have been on this forum for awhile now.

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post #20 of 251 Old 09-26-2008, 10:01 AM
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Iv'e never heard of this either. I'm at 180k. Could these bolts been from a bad batch or something? The bolts that break could they have been from engines that have been removed b4 and maybe over torqued when reinstalled or might not have been tightened enough.
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post #21 of 251 Old 09-26-2008, 11:59 AM
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I remember reading somewhere that there was a problem with some of the fasteners being too long so they would not properly torque, I think Collins Brothers jeeps released this information from their personal findings/fixes but I can't seem to find the article now.

As for Grade 8 I would not do it, grade 5 should be fine IF they are properly torqued, you don't want to pull the threads out of the block nor as somebody else stated, if it does fail, good luck getting it out.

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post #22 of 251 Old 09-26-2008, 08:13 PM
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hey that happen to me i have a 95 xj
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post #23 of 251 Old 09-26-2008, 08:36 PM
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I've never had one fail. Or witnessed it in person.

MORE sells upgraded mounts.


Anyways, I'd recommend using them over the stock ones, as they definatly wouldn't fail. Steep price though. However, if the failures are THE BOLT and only the bolt (I would assume damage to the bosses to be as a result of the bolt failing), simply swapping in Gr8 hardware is probably the easiest acceptable solution. With about a 30% increase in strength, the fatique life of the fastener would be much longer... And I mean MUCH longer. I'd have to do some reading to remember how the relationship works exactly, but I'd expect no less than a 10X increase in life. And about the worry of pulling the threads out... I'd assume they're UNC (coarse) threads. I believe you only need about a 5 or 6 thread engagement in aluminum (2024 T3) before the strength of the threads is higher than that of the bolt. Given we're dealing with cast iron, I'd not worry.

The stock brackets are kinda hokey though.
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post #24 of 251 Old 09-26-2008, 09:38 PM
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saw it happen to my buddies xj. 94 i believe. anyway i told him to buy me an engine hoist and a case of beer and i would do it for him instead he sold it for $200. Dumb@$$. I would have given him more than that
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post #25 of 251 Old 09-26-2008, 10:26 PM
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The factory bolts are 16mm heads on 3/8-16 NC threads. This seems like a rather small bolt me, even if there are three of them. Also, I don't particularly like the cantilever design of the bracket attached to the engine. There is a lot of leverage applied to those bolts. They stretch (the grade 5's) get loose, and then begin to fatigue from the flexing of the mount.

Ace Hardware, standard grade 8, 3/8-16 NC.

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post #26 of 251 Old 09-29-2008, 06:48 PM
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Thanks for the warning! I retorqued mine today. One of the right side bolts was indeed loose... all the others were tight.

181,923 miles.

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post #27 of 251 Old 09-29-2008, 08:02 PM
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Happened to my 95 xj 5 speed i had too about 3 years ago right around 200,000mi..lost the radiator because i just ran it home like it was..shifter and tranny were sitting way down and to the right..couldnt put it in reverse because was hitting on the console. This seems to be a really frequent thing with the 95 models??? Have a 98 now with 102,000 and not a single mount problem.
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post #28 of 251 Old 09-29-2008, 08:20 PM
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i'm waiting for my brown dog motor mounts... should be here this week..
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post #29 of 251 Old 09-29-2008, 08:21 PM
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those easy outs pictured are snap on, i have them, they are nice, but once you get the bolt out its hard to get the bolt of the easy out..
If the stock bolts are 3/8 coarse, why and how could they have a metric head??? Ive never heard of such a thing??
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post #30 of 251 Old 09-29-2008, 09:24 PM
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my 97 is equiped with brown dog mounts and grade 8 bolts
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