98 4.0 motor mount replacement - JeepForum.com

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post #1 of 16 Old 09-15-2013, 10:16 AM Thread Starter
coralman
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98 4.0 motor mount replacement

Replaced my mounts in prep of doing the manifold/header work. First thing was to remove the airbox. 3-13mm bolts. They have nuts on the other side so don't let them get away from you. Then remove the steering box cover which is 1-13mm nut.

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You can see the upper mount to frame bolts, and now have a little more room to move around. But first jack the motor up just a bit to support it. I used a 6x6 block underneath the deep part of the pan but clear of the raised portion for the drain plug. The mount rear upper bolt is obstructed by the steering shaft and I used a crow foot to break it loose and a cocked socket to remove it. All mount to frame bolts are 15mm. The lower sill bolts are easy to remove with standard stuff. I put some penetrant on the 18mm mount through bolt and removed it. I played around with the jack until I had the least amount of tension on the bolt and tapped it out with a rubber mallet as far as it would go, then used a long extension against the head of the bolt to drive it the rest of the way out. I used a small pry bar to break the mount loose.

Getting it out of there was kinda a pain and I wound up taking the fuel line support brackett off the manifold for wiggle room to get it up and over enough to bring it out above the vehicle end of the upper control arm.

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Originally Posted by HighLonesome
lol...if life is as a simple as a 5.9 making you happy, I'd say go ahead and buy it on impulse. ZJs are the way of Zen. Wax on, wax off
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post #2 of 16 Old 09-15-2013, 11:08 AM Thread Starter
coralman
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Continuation. Once the old one was out it looked pretty bad, compressed and cracked. The exhaust leak probaly had taken its toll also. I will make a heat shield when the new exhaust goes in. Compared to the new one there was quite a difference. The new mount bottom mounting points looked different but it made no difference. Install all the bolts loosely as they will get torqued down once the weight is on both mounts. I had to raise the motor another 1/2 inch to get the through bolt back in. Install the fuel line brackett.
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The right side was alot easier. Taking the 18mm through bolt out was easier to do from the bottom. The 4 15mm bolts for the mount were easier too except the bottom bolt closets to the firewall wanted to get trapped. So I used a flex ratchet wrench to get it out. I guess cause I had raised the motor 1/2 inch on the other side the through bolt just pulled right out without coaxing. The mount came out between the rubber discharge and suction lines. This side didn't look as bad as the left side but it needed to go. Install mopar mount#52058502 back in the same way. Install the bolts loosely until the jack is gone. I final tightened the bolts in this sequence, lower mount bolts, upper mount bolts, through bolt. Tighten all mount bolts to 48ft lbs.and the through bolt to 89ft lbs and you are good to go.

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After the trans and motor mounts were installed I noticed a good deal of elemination of in cab vibrations. Was definately worth the work.

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Originally Posted by HighLonesome
lol...if life is as a simple as a 5.9 making you happy, I'd say go ahead and buy it on impulse. ZJs are the way of Zen. Wax on, wax off
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post #3 of 16 Old 09-15-2013, 03:38 PM
Oldfrog
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Great write up, coralman !
This repair is on my list, so your write up will be especially helpful and save time. Thanks !

2007 5.7 Hemi, Ltd. QD II -
1997 ZJ, 4,0 select trac, Up country, track lok.
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post #4 of 16 Old 09-15-2013, 03:56 PM Thread Starter
coralman
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YW Oldfrog! I just do these to rake in the millions for technical writing .

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Originally Posted by HighLonesome
lol...if life is as a simple as a 5.9 making you happy, I'd say go ahead and buy it on impulse. ZJs are the way of Zen. Wax on, wax off
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post #5 of 16 Old 09-20-2013, 08:16 PM
Uniblurb
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Real nice write-up coralman and great photos too! I'm sure in just turning over 200K my mounts could use replaced too!
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post #6 of 16 Old 09-21-2013, 03:14 AM
Oldfrog
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Millions, I tell ya !

2007 5.7 Hemi, Ltd. QD II -
1997 ZJ, 4,0 select trac, Up country, track lok.
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post #7 of 16 Old 05-03-2014, 11:52 AM
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really need to do this, just dreading it haha. Great write up!

His:00 TJ "Fiona" stuff/stuff/stuff
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post #8 of 16 Old 05-03-2014, 02:19 PM
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On my 93 4.0L, you have to remove the oil filter adapter to get the passenger side through-bolt out. Fortunately, I have an early 93 (actually built in mid-92) which uses a standard 16mm hex head on the filter adapter bolt.
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post #9 of 16 Old 05-03-2014, 02:59 PM Thread Starter
coralman
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Thanks for the addition AV!

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Originally Posted by HighLonesome
lol...if life is as a simple as a 5.9 making you happy, I'd say go ahead and buy it on impulse. ZJs are the way of Zen. Wax on, wax off
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post #10 of 16 Old 11-10-2015, 06:13 PM
AlamoJeeper
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Thank you for your time posting this. I'm using the info while changing mine.

For what it's worth, on my '95, I tried removing the three bolts in the bottom of the air box. Didn't work so well. Looked at the Factory Service Manual. It said remove the three nuts from below the vehicle. So I laid on my back and took them off. I don't know if the '98 is different.

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- 1995 4.0L ZJ NP249 - mostly stock
- 2008 Jeep Patriot 5 speed Manual 4X4 - for sale, great car.
For an equipment list, go to http://www.jeep.com/webselfservice/jeep. Under "YOUR VEHICLE", click "Equipment Listing". Then enter the VIN (all caps). It will work at least to 1993.
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post #11 of 16 Old 11-10-2015, 09:29 PM
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Curious Alamo if those looked like regular nuts on the bottom of your 95 air box bolts? IIRC those are some strange nuts on my 96 which had a plate with spring underneath. I too removed them from underneath, like the 96 FSM states, and they were salt seized. Believe maybe the spring is somehow supposed to put tension on them but didn't work.

In the 94-96 ZJ parts list (p.14-850) they show an odd shaped nut with no part number listed. Just says, "Nut (Not Serviced)".

Still need to replace my motor mounts and I'll be following this real good thread! Thanks again coralman.
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post #12 of 16 Old 11-11-2015, 12:40 AM
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Quote:
Originally Posted by Uniblurb View Post
Curious Alamo if those looked like regular nuts on the bottom of your 95 air box bolts...
Starting in the air box headed downward, I had the three bolts, three rubber grommets, and then three nuts shaped like a round circle with two projections on opposite sides of the circle. These round circle nuts held the bolts to the airbox and the grommets. With the airbox in position in the engine compartment, the bolts projected down through the plate on which the airbox sits. The regular nuts which held the airbox in the engine compartment were on the underside of the plate. When I tried to remove the bolts by turning them, everything turned and I didn't accomplish anything. When I read the service manual and went in underneath the Jeep and removed the three regular nuts underneath the plate, the airbox lifted out of the engine compartment.

As you've mentioned in the past, there are changes between the '95 and later models. I don't know if that is one of the things that Jeep changed.
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100_1763.JPG  

AlamoJeeper
- 1995 4.0L ZJ NP249 - mostly stock
- 2008 Jeep Patriot 5 speed Manual 4X4 - for sale, great car.
For an equipment list, go to http://www.jeep.com/webselfservice/jeep. Under "YOUR VEHICLE", click "Equipment Listing". Then enter the VIN (all caps). It will work at least to 1993.
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post #13 of 16 Old 11-11-2015, 01:01 AM
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I did my driver's side this evening. My old and new mounts looked like the top two pictures in Coralman's second post above. The old mount was definitely sagging a bunch.

AlamoJeeper
- 1995 4.0L ZJ NP249 - mostly stock
- 2008 Jeep Patriot 5 speed Manual 4X4 - for sale, great car.
For an equipment list, go to http://www.jeep.com/webselfservice/jeep. Under "YOUR VEHICLE", click "Equipment Listing". Then enter the VIN (all caps). It will work at least to 1993.
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post #14 of 16 Old 11-11-2015, 04:17 AM Thread Starter
coralman
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Thanks for your input Alamo!.My memory gets fuzzy sometimes between the time I actually do the job and post the DIY. You are correct in that you just need to remove the nuts. I did insulate the driver side mount against header heat since I was running the apn header. Surprisingly, the stick on heat foil has stayed on it, which I really didn't expect it to.

Info on projects and repairs categorized by system
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Originally Posted by HighLonesome
lol...if life is as a simple as a 5.9 making you happy, I'd say go ahead and buy it on impulse. ZJs are the way of Zen. Wax on, wax off
coralman is online now  
post #15 of 16 Old 11-11-2015, 12:22 PM
Uniblurb
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Quote:
Originally Posted by AlamoJeeper View Post
Starting in the air box headed downward, I had the three bolts, three rubber grommets, and then three nuts shaped like a round circle with two projections on opposite sides of the circle. These round circle nuts held the bolts to the airbox and the grommets. With the airbox in position in the engine compartment, the bolts projected down through the plate on which the airbox sits. The regular nuts which held the airbox in the engine compartment were on the underside of the plate. When I tried to remove the bolts by turning them, everything turned and I didn't accomplish anything. When I read the service manual and went in underneath the Jeep and removed the three regular nuts underneath the plate, the airbox lifted out of the engine compartment.

As you've mentioned in the past, there are changes between the '95 and later models. I don't know if that is one of the things that Jeep changed.
Some real good info Alamo and thanks for the photo!
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