Rear caliper bolt falls off

[DFrank]

Truck is an 05 Dually 4x4.

one of the two big retention bolts has fallen off for the third time, since doing brakes on June.

After it happened once, my son checked the torque spec and used locktite on the second one.

It has now happened three times, and he does not know what else to do to keep it on.

We were unable to find one in the mountains on a sunday afternoon, and had to leave the truck at a friend's house, setting us up for a 5 hour retrieval mission.

At least he thought to check and noticed, so we didn't lose brakes while towing a trailer in the mountains.

 

[petersonj]

It is my guess that the clamping conditions for the fastener (the large bolt) are not being met. A large fastener must be stretched in order for the clamped parts to remain tight. Loctite does not do this. Proper torque will be useless if the fastener bottoms out or the mating parts have improper contact.

I would remove the caliper completely and inspect for proper contact of the two mating parts - are they flat, are they aligned, are they making full contact without the fastener, is the fastener bottoming out, etc.?

- John

 

[Ozymandias]

I started to use Loctite on these bolts after I lost 3 of them, always after driving washboard.
Since I loctited i never again lost one.

But I also never used a Torque Wrench on these M8 bolts, just tight and good to go.

 

[DFrank]

Thanks Ozy. Nice to know we are in good company

 

[seafish]

Also given the amount of dust and dirt those calipers are exposed to I’d suggest using acetone to clean the threads on both surfaces before applying the loctite

 

[AH64ID]

What are you torqueing them to?

 

[bcbender]

looks like it should be 135Nm (100lbft)

 

[AH64ID]

looks like it should be 135Nm (100lbft)
View attachment 131802

Which is why I asked, there are different FSM's layouts. That appears to be the LD section. HD calls for 197Nm (145 ft.lbs).

 

[bcbender]

Interesting Point,... In the text (2004 FSM) they list the LD spec, and in the chart they show both... I never had issues but I guess I only checked the SPEC page when I did mine!... I now will double check before posting incorrect information...

 

[MGreer]

I thought the OP was talking about the caliper bolts, the adapter bolts are what torques to 145. I would think the caliper bolts would break at 145.

 

[BigPapa]

I would think “one of the two BIG retention bolts” would be the bracket bolts.

 

[AH64ID]

I would think “one of the two BIG retention bolts” would be the bracket bolts.

That was my thought too.

 

[User113]

While we're all making assumptions, why was it assumed to be the rear caliper and not the front one?

 

[AH64ID]

While we're all making assumptions, why was it assumed to be the rear caliper and not the front one?

Probably because he said “Rear caliper bolt falls off”??

 

[MGreer]

Thats why I posted about the caliper bolts, I read the title.

 

[AH64ID]

Thats why I posted about the caliper bolts, I read the title.

However there isn't a bolt called the "caliper bolt" in the FSM (attached to post #8), which is why the #1's post reference to the "two big retention bolts" seems important, as does the reference to the checking torque since the only caliper bolts are the ones referenced above at 145 ft.lbs. The smaller ones are called caliper pins at 22 ft.lbs.

I guess @DFrank needs to clarify. If he only changed the pads or pulled the caliper then the only thing that should need torqued is the caliper pins at 22 ft.lbs, but if he replaced the rotors then he would also have to torque the caliper adapter bolts at 145 ft.lbs.

 

[Blakers]

I've had one fall out a few times. Since it's only one bolt, the caliper will just hang on the other bolt and usually rub the inside of the wheel, giving a grinding sound. It usually did it when I was working gas wells and running dirt roads all the time. Lock tite seemed to help, but slopping them up with antiseize and getting them tight worked too.

 

[User113]

Probably because he said “Rear caliper bolt falls off”??

Thanks, I need a reality check on a regular basis.

 

[DFrank]

Thanks for everyone’s help. Yes it’s the big bolts that hold the calipers on. I think he replaced calipers and rotor, but I may be misremembering.

he has driven it with one bolt in, but it seemed like a poor decision to knowingly do so for 200 mountain miles with a trailer.

Bolt is back in, but at this point I expect them to keep
Falling out, until we redo them with better “glue” whatever that really is.
Sounds like cleaning the bolts and holes and applying more lock tite is the call. These bolts do come with some red thread locker pre-applied to them, but it has proved inadequate.

 

[AH64ID]

@DFrank caliper adapter bolts or caliper pins? There aren’t any big bolts holding the caliper in place, just smaller pins.

What is he torquing them to?