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Question about fluid-filled engine mounts on CRD
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=8162		 Page 1 of 1
Author:  LibertyCRD [ Wed May 03, 2006 10:00 am ]
Post subject:  Question about fluid-filled engine mounts on CRD
I've read of several people that have noticed a "thumping" noise like something is loose coming from the front area of their CRD. I also have always felt and heard this noise, especially while off-road on rough terrain. Some of these guys have traced the problem down to the engine mounts. They get in there to crank the nuts down on the engine mounts some more, realize that they do indeed take more tightening, and assume that they were loose from the factory.

My question is this...Jeep installed fluid-filled special engine mounts of some kind on purpose to cut down on vibration inside the cabin from the diesel engine. Could it be that these engine mounts are not supposed to be so tight? Could it be that a little movement ("thumping") of the engine is normal because of the type of engine mounts used on these? Could it be that if we crank them down tighter in our driveway that we'll reduce the usefulness and purpose of the mounts?

Or are they really loose and need to be tightened? :?
Author:  europachris [ Wed May 03, 2006 10:14 am ]
Post subject: 
Our 'thumping' manifested itself upon coming to a full stop (like at a stop sign) and then accelerating. It would some times happen when making a tight turn, also.

I could feel it right through the passenger side floor boards, and hear it clearly. Felt like something was shifting around.

The dealer torqued down the mount bolts and all is well now. It did NOT do this since new, but came about after 20K miles.

Actually, the engine seems to be quieter and vibrate LESS since the bolts were torqued. Also, the mount should have no direct bolt connection through the vibration absorbing part. It's strictly bolted to the engine and to the frame, and the vibration absorbing part is a sandwich in the middle.

Chris
Author:  LibertyCRD [ Wed May 03, 2006 10:19 am ]
Post subject: 
europachris wrote:
Actually, the engine seems to be quieter and vibrate LESS since the bolts were torqued. Also, the mount should have no direct bolt connection through the vibration absorbing part. It's strictly bolted to the engine and to the frame, and the vibration absorbing part is a sandwich in the middle.

Chris


I understand this. But that's what I am talking about...the absorbing part is a barrier between the engine and the frame of the vehicle. That's the only logical way it could work. So the more you torque that bolt down, the more vibration absorbing ability you are going to rob from the mount. That's why I'm asking before I go out to do this on mine. I want to make sure it's OK to do this before I break out the ratchet and sockets.

Thanks for the reply.
Author:  tired_old_dave [ Wed May 03, 2006 11:23 am ]
Post subject:  jdreckard is the one to thank
Didn't torque mine down and didn't even pull out the shop manual on cd. It seemed to take less than a turn of the nut and then it "bottomed out?". Only other experience is torque snapping the old fashioned rubber block mounts on a 472ci '68 cadillac.
Author:  spoonplugger1 [ Wed May 03, 2006 1:24 pm ]
Post subject: 
Why would the motor mount change characteristics by torquing the bolts? They are not mechanically attached in any way except throught the isolator which is bonded to each plate.
Author:  LibertyCRD [ Wed May 03, 2006 1:28 pm ]
Post subject: 
Because if they were not attached in any way to the engine or frame then they would not be able to do their job. The vibrations have to go through the isolators somehow in order for them to be able to dampen the vibes. And the only way for that to happen is if the isolators are "in-line" with everything else.

Anyway, I'll look at mine in more detail one morning this week when the engine isn't blazing hot. :wink:
Author:  greiswig [ Wed May 03, 2006 1:55 pm ]
Post subject: 
If I'm understanding this right, I think I might be able to clear up something about why cranking the mounts down won't affect the mount cushioning.

The cushion has two sides, one that mounts to the engine, one to the frame. Those sides are usually what get bolted in place, and torqueing the bolts/nuts merely seats that side firmly against the respective surface...it doesn't compress the cushion at all.

Hope this helps...
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