JMOliver
NAXJA Forum User
- Location
- North Carolina
How tight should the threw bolts be tightened? I know the instructions say not to over tighten.
Thanks
JMOliver
Thanks
JMOliver
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Brown Dog MM ?
- Thread starter JMOliver
- Start date
crimsondragon
NAXJA Forum User
- Location
- NJ
I did mine fingertight, then a quarter turn over with a wrench.
- Location
- WA state
I read in another thread about BD mounts, that if you have decent vibes to back off half turn.
magimerlin
NAXJA Forum User
- Location
- Flatonia, Tx
This is true. If you got the poly mounts do not tighten them like a regular rubber mount. If you do you will have alot of vibrations. I have poly on both my 89's and just snugged them up and all is fine.
Bjorn86
NAXJA Forum User
- Location
- Montrose, CO
This is copied and pasted straight from the instructions Brown Dog sent me:
Through-bolt tightening instructions: When you install the through-bolt that attaches the motor mount to the engine bracket, do not over-tighten. If you over-tighten this bolt, you will get more engine vibration, especially in uni-body cars like the XJ. The nut MUST be a lock nut, or stop nut. If you need to reuse a worn locknut on a temporary basis, use red thread locker such as Loc-Tite. Tighten the through-bolt snug ONLY.
This is what “snug” means: Tighten ONLY until you can no longer rotate the ½” washers with your fingers. If you are using OEM through-bolts, you might want to add washers so you can use this technique.
Through-bolt tightening instructions: When you install the through-bolt that attaches the motor mount to the engine bracket, do not over-tighten. If you over-tighten this bolt, you will get more engine vibration, especially in uni-body cars like the XJ. The nut MUST be a lock nut, or stop nut. If you need to reuse a worn locknut on a temporary basis, use red thread locker such as Loc-Tite. Tighten the through-bolt snug ONLY.
This is what “snug” means: Tighten ONLY until you can no longer rotate the ½” washers with your fingers. If you are using OEM through-bolts, you might want to add washers so you can use this technique.
I'm interested in this as well. I installed my BD MM (rubber) in my '01 XJ about 2 weeks back. Tightened up the frame bolts pretty tight and snugged up the thru-bolt wrench tight as well. LOTS of vibrations upon start up. Sounded like a poor running diesel almost... So I backed off the thru-bolt nut 1/2 turn and it is better, but still quite a bit more vibrations than OE. I think I may back them off just a bit more and see if that does anything. Even though I added blue lock tite to the thru bolt, I'm afraid if I back the nut off too much it may eventually come off all together while I'm driving. I also don't have the time to visually check that nut each week.
Thinking I'll have my wife sit in the XJ while I back off the nut a bit and see if she can tell if anything changes. She actually rode w/me this past Sunday for the first time since BD MM installation and she thought my jeep was running really rough or something was wrong. :\
Thinking I'll have my wife sit in the XJ while I back off the nut a bit and see if she can tell if anything changes. She actually rode w/me this past Sunday for the first time since BD MM installation and she thought my jeep was running really rough or something was wrong. :\
Bjorn86
NAXJA Forum User
- Location
- Montrose, CO
It sounds like you still have those through bolts too tight. If it were me, I would just go buy some new lock nuts and some washers and do like they say. It doesn't sound like they want you to get those bolts very tight at all. My rebuild kit is coming this week and that is what I plan on doing since I'm using the stock through bolts again.
I've had my BD motor mounts - rubber - in for about 18 months, and they still have more vibrations than the XJ did previously with the stock mounts. Before they wore in a bit, I was really surprised by the vibes, and have even loosed the nuts and bolt heads off the mount itself about .25 inch, so there's no metal-on-metal contact.
Ultimately, the quality welds and material thickness of the BD mounts are a mixed blessing: they secure the engine better, but also transfer vibrations.
Ultimately, the quality welds and material thickness of the BD mounts are a mixed blessing: they secure the engine better, but also transfer vibrations.
- Location
- WA state
They are more beef, and slightly less "transfer material", poly or rubber. There is less movement due to the better-made mounts. So, there will be more vibes. Of course being less with the rubber. I am sure that the BD mounts will outlast most of the heep's they are installed in.