Rear Motor mount issue

[NotSoSlowSHO]

Im probably just going to resort to Loctite for this bugger, but in case I am missing something here...

My rear motor mount nut, where it mounts to the sub frame, will not stay torqued. I torque it to spec, then drive 15 miles and the entire engine feels like it's having a party under my hood. I can feel it through the floor and the shifter. Then I drive it back to my shop, jack it up, torque it down again, and repeat.

Ive done this three times now. squint

VERY annoying.

Any tips? Thoughts?
Is there supposed to be a washer between the nut and the subframe?

 

[AutoSHO]

What is the torque value on that thing?

Did you paint the subframe while you had it out? If that is the case, it may simply be the paint deforming under the mount and allowing the mount to loosen. I did not have a torque wrench of a high enough value when I reassembled my car after the clutch, so I just got it as tight asi I could. I figured on something that big, I was not going to hurt anything. If you are torquing it to spec (or more) and it is still coming loose, give loctite a try. Seems a little weird, however. Is there something causing the mount to not sit flat on the subframe?

 

[NotSoSlowSHO]

Helms states 40-55 lb ft.

The last time I tightened it I went to 65. It took a bit longer to work loose, but it did eventually.

This is just crazy. nono

I did paint the sub frame BTW. But the last time I pulled the nut off (to check the threads, and clean it out) , it was clear to see that the mount was moving. The nut had ground off any nearby paint by it's movement in the oblong hole in the subframe.

Thanks for the response, Ive going for the loctite, and 75 lb ft. evil_gri

 

[AutoSHO]

I would guess I gave it 100-110 Ft Ibs. Those nuts are BIG, and so are the studs... I do not think you are gonna hurt anything.

 

[Blue-By-U]

Whoa, never heard this one before. I better check mine next time I'm under the SHO.

Let us know how it goes.

BTW, did you install a new mount when you replaced the clutch? If so, did you intall the mount with the subframe on or off the car?

 

[NotSoSlowSHO]

The rear mount was fine before the clutch job. And was never removed from the engine. The front was replaced, but not because of failure. I just wanted the peice of mind.

I guess I will set the torque wrench for 102 lb ft finger

 

[AutoSHO]

I honestly was really worried more with it coming loose. I figured on a nut/bolt that big that I was not gonna be able to hurt it (Ask Jason, I'm not a particularly big guy) so I just used the 1/2 drive breakover and went to work. No problems thus far!

I think 80-100 Ft Ibs is more than safe.

 

[91taurisho]

AutoSHO:
Ask Jason, I'm not a particularly big guy

He can ask me too... finger He's kinda tiny...

J/k Chris.

 

[yamahaSHO]

He's got the height I have always wanted though...

<small>[ February 17, 2004, 04:20 AM: Message edited by: yamahaSHO ]</small>

 

[Bizzy]

Far be it from me to argue over torquing proceedures, but I really think you should re-think this over before you go that far over the torque spec. Overtorquing actually reduces (not increases) clamping force in many cases, by stretching the studs or threads beyond their ability to respond - especially when this is done repeatedly. Overtorquing can also cause other problems such as cracked, seized, or cross-threaded nuts (which cannot apply the appropriate clamping force), and increases the frequency of stud failure.

Re-trace your steps to see if there is something that was missed, and that nothing is damaged. If not then try some loctite on the threads and let it set up overnight before driving the car.

My .02 worth FWIW.

<small>[ February 17, 2004, 07:48 AM: Message edited by: Bizzy ]</small>

 

[sdpatt]

Read the AutoZone procedures with torque values through the service procedure topic at the top of this subject. If the bolt is coming loose with the torque you are applying, somthing is not right. Either the bolt or nut is stripped or there is something interfering with a solid coupling between the mount and the subframe.

 

[NotSoSlowSHO]

Ive read the procedures, over and over... And have looked at the issue over and over...

Damn, maybe tonight Ill pull the entire mount out for a look-see shrug

 

[NotSoSlowSHO]

Okay, I am still amaized at how such simple things become such major PITA's. squint

I pulled the entire mount out this evening. It looked great. No separation, no signs of any kind of failure. The surface between the mount and the subframe was clear and clean. The threads on the studs looked great. I examined the nut very closely as well. All looked good.

WTF??

So, I reinstalled it, torqued the mount to motor bolts down, then applied a bit of blue loctite to the large nut and torqued the mount to subframe portion down to 65 lb ft.

Then I took a long drive.
20 miles later all is well. No more rock and roll.

I dunno what to think
Ill keep you posted on this. My gut feeling says that it will work loose... AGAIN madflame

<small>[ February 18, 2004, 12:09 AM: Message edited by: NotSoSlowSHO ]</small>

 

[Blue-By-U]

Weld it on, and pray you don't have to EVER drop your subframe again wink

 

[Bizzy]

Blue-By-U:
Weld it on, and pray you don't have to EVER drop your subframe again wink

eek! eek!

 

[NotSoSlowSHO]

OKay, I am totally ****** off now... madflame and at a loss for words.

It loosened again.
headbang

HELP!

could th stud be pulling through the mount itself? How are these mounts constructed?

 

[AutoSHO]

Have you inspected the Nut and stud for any deformities?

That is really weird. How tight was it when you removed it? Did it have threadlocker on it then?

 

[NotSoSlowSHO]

yes, I inspected the nut and stud very closely.
I think I will try to find a replacement nut this weekend.

There was no loctite on the nut when removed, or any that i could see.

It was VERY tight when I removed it. Probably in excess of 100 lb ft. But I figure it was from a bit of corrosion.


Im still confident that the mount is fine.
I think I will try a bit of red loctite tonight.
If I need to remove it again, Ill just need a bit of heat.


This still just baffles me

A few questions:

How is the stud fixed to the mount itself? could the stud be pulling thru the mount?

Also:

Is there suposed to be a washer between the nut and the subframe? I do not have one.

Thanks for ANY help hail

 

[Blue-By-U]

I didn't see a washer on my older 89 or current 92's rear mount nut.

 

[AutoSHO]

No washer under it on mine.