Forums/Z31P/z31-repairs-forums suspension-chassis-and-brakes-aa/Rear caliper rebuild and piston position
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Z_Karma: (2020-02-14 22:55:39)
I just rebuilt a set of 88 rear calipers off of SS 683 with 2 Raybestos PN:WK1541 seal kits to replace 2 seized rear calipers on SS 820.
The rebuild went well and they're installed and the lines are bled. However, the pedal travel to stop seems to have noticeably increased. (full disclosure, there are z32 calipers up front)
When i reassembled them, i rotated the pistons in all the way and clocked so that a piston notch aligned with the pin on the brake pad, which are pretty new.
The FSM does not say anything about rotating the piston, except inward to clearance new pads.
Should I need rotate the pistons outward to take up some slack in the piston travel or, will they sort themselves out.
Strange that in the 25 years that i have owned these cars, i have never needed to rebuild the rear calipers before.
mwolvinm: (2020-02-17 17:35:42)
It's been a while since I've done the brakes, but as long as the notch in the piston aligns with the pin in the pad, it should be OK. When you say pedal travel to stop, do you mean that you have to push the pedal farther to engage the brakes, or that when you feel pressure, there's not as much room to the floor?
Also, does the pedal feel like it's sinking slowly when you hold pressure?
Z_Karma: (2020-02-19 00:37:39)
Yeah, it feels like there is more travel before the brakes engage. But after inspecting the old calipers, they were seized with a nice ring of rust around the piston so i bet they weren't retracting fully when i let off the pedal and that is why the pedal felt firmer with them. I couldn't even rotate one of the pistons fully out, so they are only suitable as cores.
When it gets a bit warmer, i'll bleed the rears again, as id does kinda feel like air in the system and see if that firms up the pedal and decreases the travel before i get up under the dash and mess with adjustment. I did my best to bench bleed the calipers before putting them on the car.
I'm guessing that the internal screw is a self adjustment mechanism of sorts.
mwolvinm: (2020-02-25 17:26:43)
I don't think I've ever bench bled a caliper. All of my replacements have been in a parking lot. [archived image: confused.png] In my experience, spongy pedal is either a leak somewhere or air in the system.
The internal screw is a self adjustment for pad runout. keeps the piston close to the pad while the pad wears.