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-   -   Motor moving forward when accelerating (http://www.jeepforum.com/forum/f11/motor-moving-forward-when-accelerating-1516735/)

97hero 04-30-2013 09:18 AM

Motor moving forward when accelerating
 
Hello Guy's,
nube here...I have a 97 XJ my motor is moving forward when I take off from a stop and the power steering pulley is hitting the electric fan, if I hold the brake and give it some gas it doesnt seem to touch it but accelerating from a stop I can see the motor moving forward...is this normal movement? or do I have a broken motor mount? it would seem if the motor mounts were bad it would tilt more when braking and giving it gas, but doesnt seem to move that much only when taking off, could this be a transmission mount letting it jump forward? any help would be greatly appreciated.

kaitlynsdad 04-30-2013 09:23 AM

sounds like you have a broke mount somewhere does it do it in reverse

97hero 04-30-2013 09:30 AM

No, I havent noticed any problems in reverse...and only when taking off at first then it stops, if I take off real slow then give it more gas it doesnt do it either. Thats why I was thinking transmission mount but not sure.

habbyguy 04-30-2013 09:32 AM

If you're not getting a lot of twisting in the motor (left to right movement at the valve cover), I'm betting it can only be the transmission mount. Easy enough to check, especially if you can get a jack under the tail of the transmission and give it a little lift to see if the mount's rubber separates. I'll bet dollars to donuts it will...

97hero 04-30-2013 09:35 AM

So the transmission mount would allow the motor to move forward just enough to hit the fan? also would it be a good idea to go ahead and change the motor mounts as well?

97hero 04-30-2013 09:51 AM

also do all 4.0's lean back a little? I noticed the motor leans back the front is a little higher...is this normal?

79chiefs 04-30-2013 10:19 AM

Yea they all lean a bit, best be to see if your lean is more than it should be is look at the trans. mount, if it is broke it can cause the back to lean down more.

97hero 04-30-2013 10:25 AM

Well, its sounding like a trans mount...is it a good idea to replace the motor mounts while I'm at it?

habbyguy 04-30-2013 12:34 PM

Personally, I wouldn't. But it comes down to the value of the (small) amount of money and time vs. the potential for problems later. I do know that my left motor mount broke and that probably caused the crack in my exhaust manifold. OTOH, the stock manifolds are "built to crack" so it might have done that later on its own, plus it gave me an excuse to buy a stainless header, so it's all good. If you are heavily into preventative maintenance it's not a bad thing to do. And if you're planning on keeping the XJ for another 100,000 miles, it's not a bad thing to do. But you can just keep an eye on the mounts and look for problems, and replace them if/when you see something wrong.

97hero 04-30-2013 12:42 PM

Thanks, I was thinking if the trans mount is bad and allowing the motor to move forward it might have placed some added stress to the motor mounts and might be a good idea to replace...but like most people, I have limited funds and want to put the money I do have in the right places and what is needed most, so I will probably just get the trans mount and like you say keep an eye on those motor mounts for now...Thanks to all for the info and help.

idaholtby 04-30-2013 12:59 PM

The Electric fan for the A/C has very little clearance between it and the Power steering pulley to begin with. Please verify that this fan is properly mounted and fastened down to the radiator. If it is not, then your issue will be amplified if bad/weak motor mounts are the cause, or improper mounting is 100% the cause. I still suspect weak/bad motor mounts, but verify this fan is properly mounted with all screws first, including that the lower tabs for this fan are in their mount and is flush up against the radiator. The transmission mount will cause more of a rotational torque movement if bad, not so much a fore and aft movement.

97hero 04-30-2013 01:11 PM

I checked the fan and it is in correctly and fastened down as flush to the rad as it can be, I did notice it is a very tight fit not much space between the pulley and fan, if bad motor mounts it would tilt under stress (side to side) correct? I get the problem when taking off from a stop the motor is actually moving forward...in your opinion is this a symptom of bad trans mount does it allow the motor to move forward when it fails?

idaholtby 04-30-2013 01:40 PM

Quote:

Originally Posted by 97hero (Post 15369287)
I checked the fan and it is in correctly and fastened down as flush to the rad as it can be, I did notice it is a very tight fit not much space between the pulley and fan, if bad motor mounts it would tilt under stress (side to side) correct? I get the problem when taking off from a stop the motor is actually moving forward...in your opinion is this a symptom of bad trans mount does it allow the motor to move forward when it fails?

Most movement would be side to side, but still there will be a fore/aft movement under drivetrain load. Given that there is very little clearance between the A/C fan and Power steering pump to begin with, there is no room for error.
Pretty much has to be the motor mounts as the cause. Can't think of another contributor that would cause this aside from the fan mounting which you just ruled out.

97hero 04-30-2013 01:44 PM

So it couldnt be the trans mount? most likely motor mounts?

idaholtby 04-30-2013 01:50 PM

Quote:

Originally Posted by 97hero (Post 15369466)
So it couldnt be the trans mount? most likely motor mounts?

I cannot see the trans mounts in any way causing this. It is most likely the motor mounts. Transmission mounts present differently when bad. When bad, they cannot transmit their slop through the motor mounts. Physically impossible if the motor mounts are good. Check all of your mounts though. Your motor mounts are your likely cause, but this does not mean that your tranny mount is good. They all seem to have the same lifespan.


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