[Bluesky 07]

I had retracted the caliper piston, removed the pads, and was to the point of installing the new rotor. Backed off the parking brake as some recommend and was trying to tighten it up. That little star wheel...don't get me started. Anyway, the hub wouldn't turn and but it felt like the diff, not the parking brake, that was stopping it. To be sure, I thought, "I'll put it in neutral so I can turn the hub and see if the parking brake is dragging."

Well, of course you have to depress the brake pedal to shift and of course pushing the brake pedal causes the pistons to extend and of course if there are no pads to stop the piston...



The piston will not retract even under pliers/pry bar/c-clamp/etc. I bought a new one just in case but not being familiar with repairing/rebuilding calipers, I'm wondering if I can disassemble and fix this one without a rebuild kit (I could get one in a few days but need to have this back together today).

TIA for any advice, and feel free to laugh your a**es off. I'm still SMH at myself.

[jbtvt]

Been a while since I rebuilt one but guessing you need to realign it in the hole if it's not going back in with a clamp. Would probably be easier to do with the line off and no pressure. There's also a square edged ring in there that retracts the piston, suppose it'd be possible to get hung up on that as well. Looks like your boot is in good shape so if that comes off in one piece, unless you messed up that inner ring you shouldn't need a kit (and the boot may not even need to come off)

[waypoint]

Loosen the bleeder screw, and rotate the piston while pushing it in by hand to get it back into the bore.

[Too Stroked]

^^^^ This. And do not force the piston in. You need to make sure it's square with the caliper bore.

[Bluesky 07]

Thanks to everyone who responded. I got the piston to turn, but it simply would not retract so I decided to just use the new one I bought. I’m guessing I jacked it up last night when I was trying to retract it not realizing it wasn’t aligned correctly. Live & learn!

[bob3dsf]

Honestly, It's probably just fine. If it's just a little misaligned, you should be able to take it out, square it up, and put it back in. However, This means taking the caliper off (disconnected), pulling off the dust boots, etc. It'll be messy, but not hard. I've rebuilt my fronts and its not hard at all. If it's a little more stuck because you were trying to put it back in crooked, just be careful freeing it up. You don't want to grab it with pliers or pry on it and scratch the cylinder. The outer edge/lip is a safe place to pull on with pliers. That's where it contacts the pad, as you know. I don't think it jacked at all. I would be surprised if you found it was.

The square cut seal inside the bore is what seals the system and allows the fluid pressure to act on the cylinder. it doesn't retract anything. it could, however, be what it's hung on if crooked, as mentioned.

[Drcoffee]

Its probably beyond the wear line in the bore and wont seal anymore.. Just replace it.

[Bluesky 07]

Originally Posted by Drcoffee

Its probably beyond the wear line in the bore and wont seal anymore.. Just replace it.

That’s what I ended up doing. Ran out of time and patience with it when the piston wouldn’t budge, especially when I thought how stupid I would feel if I “repaired” it only to have it leak or fail later.

[riceandpho]

Originally Posted by Bluesky 07

That’s what I ended up doing. Ran out of time and patience with it when the piston wouldn’t budge, especially when I thought how stupid I would feel if I “repaired” it only to have it leak or fail later.

its not hard to do, you might have a seal that is lodged inside.
take your time, I tore a boot and used the same procedure, use some syl-glide

03900610.pdf

[Bluesky 07]

Originally Posted by riceandpho

its not hard to do, you might have a seal that is lodged inside.
take your time, I tore a boot and used the same procedure, use some syl-glide

Attachment 402465

I appreciate the advice but it’s Advance Auto Parts’ property now as I had to turn it in to recover the $70 core charge.

[Drcoffee]

That was the best choice. The problem with brakes is the water in the fluid over many years causes the bore of the caliper and master cyl to corrode and wear out the seals. For the same reason you dont press the brake pedal all the way to the floor when bleeding the system to avoid damaging the seals in the master cyl, you can expect the caliper seals to get damaged when the piston moves too far out. The seals are old and fragile. Now that the piston has traveled too far and possibly gotten cocked in the bore, the safe bet is to replace it.

Ive done the caliper rebuild once before and you really need the right tools to hone the bore for the new seals or they will just leak in short order.

[bob3dsf]

Originally Posted by Drcoffee

Ive done the caliper rebuild once before and you really need the right tools to hone the bore for the new seals or they will just leak in short order.

I beg to differ. The caliper bores don't do the heavy lifting in terms of sealing. it's the square cut seals. Corrosion damage to the piston surface will compromise the seal. It'll allow a leak due to the rough surface damaging the rubber seal and causing a leak

Now I've never let my brake fluid get really old and have a lot of water contamination, so I've not seen heavily damaged cylinder bores. When I re-did my front's, all the corrosion was at the outer edges of the pistons where they contact the pads, and just behind the dust boot where they sit in the bores. Once the pistons were feed up, there was no damage to the bores. It was all on the piston. It looked pretty clear to me that the failure point was not rebuilding the calipers to restore the dust boots. The repeated heating cycles during braking left the boots very thin and brittle such that they all but crumbled away as I inspected the calipers during the repair job. Those damaged boots allowed water and road grime (and salt brine in the winter) to get in there and start the corrosion.

I feel fairly confident that a regular rebuild interval (in addition to fluid flushes), to allow refreshing the dust boots would go a long way to preventing seized calipers.

I soaked my calipers in metal rescue to ensure there was no corrosion present that I couldn't see. I didn't realize that there is a coating on the OEM calipers to prevent rust. The rust removing bath took that off and they started getting surface rust within a few days due to rain and usual humidity changes, etc. I don't know why I'm attached to my original calipers, But as soon as I have enough time, I plan on taking them back off to clean them and paint them. At that time, I'll check the dust boots and see about the condition of the rubber. None of it is much more work than if I were swapping the calipers. Somehow I wound up with an extra rebuild kit, so I have everything I needs if it needs it.