Repeated caliper seizing issues
- Thread starter Cezar
- Start date
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UPDATE UPDATE UPDATE
I went ahead and pulled the caliper and dis-assembled it. At first it didn't want to come apart but after compressing it and expanding it a few times it broke loose. There was a significant layer of corrosion on the piston at the seal/piston interface area which was quite obviously the culprit. The rest of the caliper was *BRAND NEW* as it's only a couple years old at this point. Glide pins were flawless.
IDK if the problem is crap mettalurgy, bad luck, or what.
In the interests of science I decided to try to fix it. I've never taken a caliper apart before and I did NOT read up on this subject so it's possible I have to redo the whole thing, but that's okay.
I basically retracted the piston with a clamp, then hit it with compressed air through the banjo bolt hole, and repeated that process a few times until it finally popped out. I found said corrosion on the piston and used 400 grit sandpaper and wd40 until the corrosion was completely gone and nothing caught my fingernail. Then to re-assemble, I stuck the seal into the hole, pressed the piston into the hole with my vice, and then once fully in I used a pick to pull the inner seal back out to where it belongs. Visually everything looked 100% and after buttoning it up and doing a test drive and checking with an IR thermometer, both axles are now showing proper temperatures on each corner.
I went ahead and pulled the caliper and dis-assembled it. At first it didn't want to come apart but after compressing it and expanding it a few times it broke loose. There was a significant layer of corrosion on the piston at the seal/piston interface area which was quite obviously the culprit. The rest of the caliper was *BRAND NEW* as it's only a couple years old at this point. Glide pins were flawless.
IDK if the problem is crap mettalurgy, bad luck, or what.
In the interests of science I decided to try to fix it. I've never taken a caliper apart before and I did NOT read up on this subject so it's possible I have to redo the whole thing, but that's okay.
I basically retracted the piston with a clamp, then hit it with compressed air through the banjo bolt hole, and repeated that process a few times until it finally popped out. I found said corrosion on the piston and used 400 grit sandpaper and wd40 until the corrosion was completely gone and nothing caught my fingernail. Then to re-assemble, I stuck the seal into the hole, pressed the piston into the hole with my vice, and then once fully in I used a pick to pull the inner seal back out to where it belongs. Visually everything looked 100% and after buttoning it up and doing a test drive and checking with an IR thermometer, both axles are now showing proper temperatures on each corner.
AuSeeker
Elite Member
If I were you I would add a rubber compatible brake grease under the rubber boot, the problem is that water is getting past the boot and causing the piston to rust, the grease will fill the space and not allow water intrusion into the boot and therefore no water getting to the piston.
Drcoffee
Senior Member
Sounds like the brake fluid has failed. Completely purge the fluid with a quality fluid, not the valvoline crap at wally world. Replace the calipers with a different brand like napa reman units. The only way the calipers seize so quickly is water in the fluid. Slapping a new caliper on is only going to rust up again
AuSeeker
Elite Member
From what I read that [MENTION=117138]Cezar[/MENTION] wrote the rust wasn't on the inside of the caliper bore where the brake fluid is in contact with the piston but instead where the piston and boot seal to the caliper, so the rust would be from water intrusion into the boot and not water contamination of the brake fluid.
Yeah the corrosion was on the outside of the piston.
I keep my brakes in tiptop shape, fluid change every two years. The entire brake system was replaced about 4 years ago when I did a total suspension overhaul. Which is why I was posting because in no way should I be seeing multiple caliper failures in this time span.
This is a great idea and I think would certainly have helped. I had some grease on there but next time I will take care to pack the boot full. I'm gonna stop replacing calipers and start rebuilding them.
fastbroshi
Member
Dow High Vacuum grease is a good option here. Expensive stuff, but I've had good results. As a barrier between the seal and the piston, it's great.
I'm curious, when you went to reassemble, did you use brake assembly lube, or brake fluid? As we all know, brake fluid absorbs water, so if you used it to assemble and push your pistons through the seals, there is most likely a small amount between each piston and its seal. So any moisture that gets past the seal is going to get absorbed by the bf and just hang out there and possibly start to corrode the piston.
Maybe that's how they initially assembled your replacement calipers.
I'm curious, when you went to reassemble, did you use brake assembly lube, or brake fluid? As we all know, brake fluid absorbs water, so if you used it to assemble and push your pistons through the seals, there is most likely a small amount between each piston and its seal. So any moisture that gets past the seal is going to get absorbed by the bf and just hang out there and possibly start to corrode the piston.
Maybe that's how they initially assembled your replacement calipers.
fastbroshi
Member
:shrug: I dunno, just throwing it out there. Something to do with the manufacturing process, or the seals' inherent design is faulty, allowing miniscule amounts of atmosphere to slip by?
Too Stroked
Member
Did you use OEM Toyota caliper rebuild parts from a Toyota dealership or aftermarket / parts store junk? Same question for the calipers themselves. Trust me, there is a big difference in quality between OE / OEM and aftermarket parts.
Drcoffee
Senior Member
Yup, what he said. I have had this happen on my is300. Caliper would not retract cause the hose was collapsed. The steel braiding under the rubber expands inward.
Runnin on E
Member
I wrote a reply over here that I believe is the real fix for this issue. What really happens is that water gets in between the dust seal/boot and the piston and sits in there. The tension of the "C" clip that secures the dust boot to the caliper needs to be tighter than they are. Plus when assembling there can be no gap or wrinkle in the dust boot where it contacts the caliper body. Just a wild guess here, but if you got your brakes reasonably hot on a regular basis (cooking out the water) it might help, or as suggested before, take your calipers off and inspection them on a more regular basis.
https://www.toyota-4runner.org/4th-...-gen-caliper-upgrade.html?highlight=stainless
https://www.toyota-4runner.org/4th-...-gen-caliper-upgrade.html?highlight=stainless
Interesting, there are no c-clips in my caliper dust boots (none of them)
