Parking Brake issue after replacement
Posted: Fri Aug 07, 2020 4:12 pm
I bought a 710m with a parking brake that did not operate. I put off the repair for a long time but got around to it this week. The job of getting everything off was a lot easier than I thought it would be and it revealed the issue. The pull arms and the pull fork were fused together and it was full of old, asbestos I'm sure, brake dust.
After removing the pull arms, I could not budge them with a vice and a big hammer to free them up so I could punch out the retainer pin. The pin wouldn't move even after grinding one end off.
I ordered new discs(already riveted to the plate), all the pull arm parts and the rubber boot and its plate. cleaned up everything and media blasted the parts. The rotor faces were all cleaned w a scotchbrite pad and looked good as did the balls etc. I lubed everything up that was required (not the ball bearings) and it worked smooth as could be. I reassembled and set everything up but the brake dragged...a lot! I readjusted and even unhooked the cable and couldn't improve the drag.
The lever arm moves the 100mm
The pull arms work freely when I push on the arms with my hand and can feel the free play then the expanding of the plates
I let it cool off and removed everything again. Noticing that the plates expanded as they should when I tested after removing the rear pad. I double checked everything but the only thing I saw was that the disc pads were a very tight fit on the splined output shaft. I test fit an old one on it and the tolerance wasn't as tight but I expected that after years of use. So i ever so lightly greased the shaft and that appeared to help the fitment. Put everything back together and it still drags. Unhooked cable and it still drags. Adjuster bolt loose and it drags.
What exactly is going on in there when the pads are spinning with the shaft when the brake is completely disengaged? What pulls them away from the rotor faces once the parking brake is released?
I'm not sure if the pads are new and super thick and will break in w use, but a 5mph run down my short driveway and back didn't do it and the truck stops suddenly when you let up on the accelerator ( as well as really heating up the assembly).
Or if the plates are expanding the pads outwards and the pads are binding up on the splined shaft and not releasing as they should.
Hopefully someone has an idea or can verify those pre riveted plates work fine so I can cross that off my list of culprits.
After removing the pull arms, I could not budge them with a vice and a big hammer to free them up so I could punch out the retainer pin. The pin wouldn't move even after grinding one end off.
I ordered new discs(already riveted to the plate), all the pull arm parts and the rubber boot and its plate. cleaned up everything and media blasted the parts. The rotor faces were all cleaned w a scotchbrite pad and looked good as did the balls etc. I lubed everything up that was required (not the ball bearings) and it worked smooth as could be. I reassembled and set everything up but the brake dragged...a lot! I readjusted and even unhooked the cable and couldn't improve the drag.
The lever arm moves the 100mm
The pull arms work freely when I push on the arms with my hand and can feel the free play then the expanding of the plates
I let it cool off and removed everything again. Noticing that the plates expanded as they should when I tested after removing the rear pad. I double checked everything but the only thing I saw was that the disc pads were a very tight fit on the splined output shaft. I test fit an old one on it and the tolerance wasn't as tight but I expected that after years of use. So i ever so lightly greased the shaft and that appeared to help the fitment. Put everything back together and it still drags. Unhooked cable and it still drags. Adjuster bolt loose and it drags.
What exactly is going on in there when the pads are spinning with the shaft when the brake is completely disengaged? What pulls them away from the rotor faces once the parking brake is released?
I'm not sure if the pads are new and super thick and will break in w use, but a 5mph run down my short driveway and back didn't do it and the truck stops suddenly when you let up on the accelerator ( as well as really heating up the assembly).
Or if the plates are expanding the pads outwards and the pads are binding up on the splined shaft and not releasing as they should.
Hopefully someone has an idea or can verify those pre riveted plates work fine so I can cross that off my list of culprits.