RAD4Runner
Senior Member
Just in case this happens when replacing brake shoes that have been on for so long and/or have gone so thin, I suggest making sure you have replacement brake cylinder handy or know where to get one quickly.
I recently replaced my rear brake shoes. The shoes part was uneventful, all parts were in normal condition (except brake cylinders as described below), although proper tool for removing and re-installing the return/tension spring would have been nice.
After the shoe replacement, left brake cylinder leaked. NAPA carries replacement cylinder for $16. I replaced them at NAPA parking lot. About a week later, the right side cylinder leaked, too. Replaced with NAPA part again without any issues.
LESSONS LEARNED post-mortem (Not much I could have done because truck was 30 years old when I got it):
1) Good idea to regularly flush and refill brake system, including the cylinders and calipers if possible. Dirty / old brake fluid promotes / allows rust in cylinder.
2) This is just the nature of the beast ...Rubber cups keep the cylinder wall that they rub against clean, smooth and free of rust. As shoes get thinner, the rubber cups inside the cylinder operate farther and farther away from the longitudinal center of the cylinder. The part of the wall closer to the center of cylinder where the cups do not rub anymore get rusted / pitted. After replacing with new brake shoes the cups and pistons will now operate closer to the center of the cylinder again - right on the rusted wall surface. This will break seal against the wall and cause a leak.
3) Cylinder can be honed, but even if the rubber cups, pistons, and seals and are still in good condition like mine (here) and (here) were, they might be too small for new cylinder bore size. Tools, supplies, and time could cost more than new replacement (and even OEM if you can find it).
4) Always have spare brake cylinder or rebuild tools and supplies readily available when replacing old brake shoes where above conditions apply.
5) This problem may not occur on front disc brakes where brake pads are replaced more often, so cups and pistons are pushed back toward the center of the caliper before rust develops.
I recently replaced my rear brake shoes. The shoes part was uneventful, all parts were in normal condition (except brake cylinders as described below), although proper tool for removing and re-installing the return/tension spring would have been nice.
After the shoe replacement, left brake cylinder leaked. NAPA carries replacement cylinder for $16. I replaced them at NAPA parking lot. About a week later, the right side cylinder leaked, too. Replaced with NAPA part again without any issues.
LESSONS LEARNED post-mortem (Not much I could have done because truck was 30 years old when I got it):
1) Good idea to regularly flush and refill brake system, including the cylinders and calipers if possible. Dirty / old brake fluid promotes / allows rust in cylinder.
2) This is just the nature of the beast ...Rubber cups keep the cylinder wall that they rub against clean, smooth and free of rust. As shoes get thinner, the rubber cups inside the cylinder operate farther and farther away from the longitudinal center of the cylinder. The part of the wall closer to the center of cylinder where the cups do not rub anymore get rusted / pitted. After replacing with new brake shoes the cups and pistons will now operate closer to the center of the cylinder again - right on the rusted wall surface. This will break seal against the wall and cause a leak.
3) Cylinder can be honed, but even if the rubber cups, pistons, and seals and are still in good condition like mine (here) and (here) were, they might be too small for new cylinder bore size. Tools, supplies, and time could cost more than new replacement (and even OEM if you can find it).
4) Always have spare brake cylinder or rebuild tools and supplies readily available when replacing old brake shoes where above conditions apply.
5) This problem may not occur on front disc brakes where brake pads are replaced more often, so cups and pistons are pushed back toward the center of the caliper before rust develops.
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