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Unread 04-30-2013, 01:54 PM   #16
BigBadWuf
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1992 XJ Cherokee 
 
Join Date: Mar 2013
Location: Greenville, Virginia
Posts: 183
Did you check if the motor mount bolts are tight where they bolt to the unibody?
The frame holes are oval and if the bolts are loose you can slide the motor back and forth with a hoist. Maybe someone had the motor out and didnt tighten them properly. If not that check the rubber in the motor mounts its notorius for seperating from the metal part, both of those would cause front to back movement. It is not the bolts that go into the motor, that would cause side to side movement.
I also suppose it could maybe be the trans mount, check the rubber on that to google a pic of a new one, and if yours looks squished compared to that its bad.

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Unread 04-30-2013, 02:12 PM   #17
idaholtby
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1991 YJ Wrangler 
 
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Quote:
Originally Posted by BigBadWuf View Post
Did you check if the motor mount bolts are tight where they bolt to the unibody?
The frame holes are oval and if the bolts are loose you can slide the motor back and forth with a hoist. Maybe someone had the motor out and didnt tighten them properly. If not that check the rubber in the motor mounts its notorius for seperating from the metal part, both of those would cause front to back movement. It is not the bolts that go into the motor, that would cause side to side movement.
I also suppose it could maybe be the trans mount, check the rubber on that to google a pic of a new one, and if yours looks squished compared to that its bad.
Good point, and needs addressed before replacing the mounts. You should be able to see where the movement is and base your decision upon this.
My expertise is mainly derived from YJ's to where the drive trains are the same, but with the YJ, the Mounts are welded to the frame, no chance of movement there.
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Unread 04-30-2013, 02:20 PM   #18
97hero
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1997 XJ Cherokee 
 
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Thanks!!!! I will check the bolts and go from there...dont want to spend $$$ for stuff I dont need. The info and experience on this forum is great...thanks again to all!
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Unread 04-30-2013, 04:06 PM   #19
habbyguy
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1996 XJ Cherokee 
 
Join Date: Feb 2010
Location: Mesa, AZ
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I've never blown the right motor mount, but can say with absolute certainty that when you blow the left one, you get a LOT of rotation of the engine (not sure about fore/aft movement, but the rotation is dramatic).

My money's still on the tranny mount. Here's why.

There are 3.0 points of contact that hold the motor and tranny in place. A motor mount on the left, a motor mount on the right, and a tranny mount in the center. The tranny mount has a lot more rubber, and is a lot bigger than the two motor mounts.

You know there are forces that will push the motor forward (or more accurately, rotate it on the motor mounts, resulting in a forward movement) under acceleration, or the OP wouldn't have this problem.

Because of the triangulation of the three mounts, if the left one broke, the motor rotates. I'm betting the same is true with the right one, but if not, it would "twist" to the left as it moved forward, being constrained by the left motor mount and tranny mount.

Seems to me that if you took away the ability of the tail shaft to remain at the same height (by breaking the tranny mount) the motor would have the ability to move by rotating around the two motor mounts - either direction could cause clearance problems.

But at any rate, checking whether the tranny mount is bad or not is so simple it's not worth worry about... put a jack under the tail of the tranny and lift it, and see if the tranny mount's rubber is separated or not.
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Unread 04-30-2013, 06:03 PM   #20
idaholtby
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Quote:
Originally Posted by habbyguy View Post
I've never blown the right motor mount, but can say with absolute certainty that when you blow the left one, you get a LOT of rotation of the engine (not sure about fore/aft movement, but the rotation is dramatic).

My money's still on the tranny mount. Here's why.

There are 3.0 points of contact that hold the motor and tranny in place. A motor mount on the left, a motor mount on the right, and a tranny mount in the center. The tranny mount has a lot more rubber, and is a lot bigger than the two motor mounts.

You know there are forces that will push the motor forward (or more accurately, rotate it on the motor mounts, resulting in a forward movement) under acceleration, or the OP wouldn't have this problem.

Because of the triangulation of the three mounts, if the left one broke, the motor rotates. I'm betting the same is true with the right one, but if not, it would "twist" to the left as it moved forward, being constrained by the left motor mount and tranny mount.

Seems to me that if you took away the ability of the tail shaft to remain at the same height (by breaking the tranny mount) the motor would have the ability to move by rotating around the two motor mounts - either direction could cause clearance problems.

But at any rate, checking whether the tranny mount is bad or not is so simple it's not worth worry about... put a jack under the tail of the tranny and lift it, and see if the tranny mount's rubber is separated or not.
Good point on the triangulation theory. YJ's will not present in this manner with a bad tranny mount. (Recent XJ owner and 16yr YJ owner). Definitely can see where (with lack of clearance on a XJ) a bad tranny mount can cause enough horizontal rotation to cause this issue under load. To the Op, as previously suggested, check the tranny mount first, but also check the condition of your motor mounts while you are at it.
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Unread 05-05-2013, 03:41 PM   #21
97hero
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Ok I replaced the trans mount and both motor mounts...they were all bad the trans mount was smashed down at least an inch from were it should be, but am still having the issue with the power steering pulley hitting the electric fan when accelerating...anybody have any ideas on this? its driving me crazy, no idea where to go from here with it...I was pretty sure it was the mounts and they did need replaced but did'nt fix the issue...what now???
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Unread 05-06-2013, 03:58 AM   #22
mayeni
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I think it is time for you to post some pictures or a video. It is very hard to troubleshoot without actually seeing what is happening. I have to ask did you install all the new mounts correct? I think it is very unlikely that the motor tilts if all the mounts are new and correctly installed. And you tell that the motor hits the fan when you accelerate. With bad engine mounts the motor is propelled backwards when you accelerate and not forwards. So maybe it is the fan hitting the motor and not the motor hitting the fan.
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Unread 05-06-2013, 09:01 AM   #23
97hero
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All mounts loot to be correct, the motor was leaning back more before the trans mount but the new trans mount lifted the back of the motor up, there is very limited clearance between the power steering pulley and electric fan as it is, maybe an inch...sometimes even hitting a bump the wrong way makes it hit, I'm at a loss trying to figure this thing out...I can get some pics of how it is sitting when I get home from work but it is hard to get pics or vids because it has to be accelerating.
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Unread 05-06-2013, 09:37 AM   #24
buildin1XJ
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Might want to try parking it in a down hill slope in park e brake on and have someone rev the engine and see whats moving.
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Unread 05-06-2013, 09:42 AM   #25
97hero
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I have tried in park, tried it with someone on the brake while giving it gas and the motor doesnt move that much, seems like normal movement...only does it from take off unless I take off super slow but if I'm trying to get into traffic it will hit the fan...
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Unread 05-06-2013, 09:53 AM   #26
97hero
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How bad would it be to pull the electric fan out Temporarily so I can still drive it until I get this figured out???
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Unread 05-06-2013, 12:49 PM   #27
79chiefs
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Not hard, few screws, unplug it, and go that way for a while, watch temp though.
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Unread 05-06-2013, 01:06 PM   #28
97hero
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Easy to get out but is the fan only for when using AC or is it needed? does it only kick with AC on or is it also used when it gets over a certain degree to help the clutch fan??? if I can run without it at least until I figure it out that would be fine not really using AC at the moment anyway...my dad has a Wrangler without AC, he is always saying rip that damn AC crap out of there...it just gets in the way...lol but I cant go without a top and doors like the Wrangler and get good air flow, so soon I will have to get this figured out...
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Unread 05-06-2013, 02:13 PM   #29
97hero
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I was told the motor movement could also be caused by the output splines being either too short or too long...or something like that and that I should remove the the drive shaft and lube the output splines...anyone ever heard of anything like this...and could it be the cause????I dont see the relation between the issue I'm having and the drive shaft.
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Unread 05-06-2013, 04:38 PM   #30
79chiefs
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Post pics of how close it is, and marks from the two hitting. Just pics of engine bay, and that area will help. Could your fan be loose? How do you know the motor is moving, because wouldn't the mech. fan hit the radiator?
Please pics.
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