While working in the engine today, I notice a circular wear pattern on the motor mount's flat washer. That seemed unusual for something that shouldn't be rotating so I checked it out and sure enough, one of two bolts on the motor mount was very loose. I was able to to tighten it to approx. the same feel and the other bolt.
Does anyone know the correct torque spec for these bolts?
Thanks!
Good catch on your visual inspection.
That is a 1/2"x 13 grade 8 bolt dry 110 lbs. lubed 80 lbs.
Mark,those mounts are made by a company called lord isolators,on some of the rubber pieces you can make out a part number.
Not sure but I think those are shoulder bolts where you tighten them until the threads stop.Reseach lord they should have info on
the site.
Those are hard plastic or very hard rubber. Not sure if they are supposed to be bolt tight. My mounts show signs of movement also . They are supposed to move a little IMHO.
The airplane versions have a sleeve to tighten to. These dont seem to.
I wil check my book wed.
Great point. The Lord website refers to these as vibration isolators, not motor mounts. I've attached a drawing of one of their isolators that looks pretty similar to the one in question. Do these wear out and need periodic replacement? If so do they age out from static load or is it a function of dynamic load, i.e., engine run time?
The Lord 2-piece isolator spec sheet (https://www.lord.com/sites/default/files/Two-Piece_Mounts.pdf) refers one to the "Tightening Torque Chart" but that's not part of the spec sheet. A quick google search turned up that info here. Looks like they are specifying standard torque values based on the bolt strength and size. The torque table is on pp123 of the Lord industrial catalog (https://www.lord.com/sites/default/files/Documents/ProductCatalogs/PC7000_IndustrialParts.pdf).
I'll try calling James at FOT and/or Lord later today and see what I can find out.
I'll look to see if I can find the part number.
Mark,I wonder if anyone has access to a vibration meter to get a reading on the mounts,we could get a before and after to see
if the new ones really help.From what I can gather the isolators on the side are the same as the rear one.
The bolt torque remains the same on these isolators or mounts what ever you call them. You never leave a bolt loose. The crush will be built into the design. Usually a sleeve.
Yep, just took it apart and you are spot on (as usual). There's a substantial steel sleeve in the center.
Lord Series SSB
Part number J-3049-67
If I'm reading the Lord torque chart correctly, it calls for 106 ft lbs dry for the 1/2-13 Grade 8 bolts.
I have a vibration meter as an app on my Android phone; it is called Vibrometer.
I have never had a need for it, so I do not know how it works. You might try that.
Trent
After taking them apart, they look fine. The rubber doesn't appear to be deteriorated from a visual inspection: it's not chalky, checked or brittle. The rubber portion seems fully bonded to the steel "washer" on each side. I'm going to reinstall, torque both of them and call it good.
On something like that should one use Loctite on threads?
John M
If torqued correctly the bolt stretch will hold the bolt without Loctite. Loctite doesn't harm anything though.
Blue would be OK, not red. Correct torque should do it but that location gets a lot of vibration. Red dust is a tell tale. Red dust around a U joint is really a bad sign.
Pierce
I reached out to Lord and here's the email conversation. Their responses are in itaclics:
MD: Good morning. I own a 2003 motorhome that uses your SSB vibration isolators, part number J-3049-67. Do these need to be replaced periodically due simply to age? Mine appear to be in good shape, but they are at least 14 years old. The motorhome has low miles (65,000), so the dynamic loads have been low.
LORD: The J-3049-67 is part of a two piece mount, SSB26-1000-1 that is still in production. In the application they most likely took a set in the elastomer. If there are no visible cracks they should probably be usable. If you are having the unit serviced you might want them replaced in the next couple of years. This mount is available through AstroTex at 972-424-8707.
MD: Thanks for the email. What does, "took a set in the elastomer", mean?
LORD: Set is defined the amount deformation never recovered after the removal of a load. As an example if these were used to support a 600 lb. radiator the height of the mount would be less than when the mount was installed new. The J-3049-67 had a height of 0.81" new. The height would be less after 14 years of service. There are no guidelines for replacement.