I've only squeezed a few pistons in my day, but ones on the back of my vette seem beyond reasonable.

The brakes do creak during slow application, and I remember the pressure guage getting jumpy when testing line pressure awhile back, all which leads me to sticking pistons.

I have on other cars been able to compress the pistons with a little prying, or just the right thickness of a wood block and some strong hands.

These ones I got my piston tool out and even that seemed to struggle and want to spread the caliper. And worse yet, it wasn't symmetrical, one side is worse than the other. The tool seems designed to spin the piston while compressing it, but that didn't happen. It has two spanner type pegs in the various attachments.. as if the piston is supposed to have somewhere for those to go. Maybe on an import?

I'm shopping for some rebuilt calipers now. Hold on to your wallets! I heard those factory children with small hands are good at these sorts of things.

AC Delco seems to be a fan of Raybestos for their Professional line. The photos are identical. $65 ea and $8 core.

I've heard of a Premium line, which is supposedly oem manufacturer, such as a GM part number, but I've never seen of it.

GM parts direct only sells the left rear caliper.

I'll be into this about $500 before all is said and done, not counting hoses. $1500 for wilwood rears doesn't sound quite as bad now.

Not an offensive question, but did you have the mc cap off?

I have always used a c clamp with an old pad to compress the piston, I don't believe I've ever done one by hand that didn't cause the second piston to pop out in balance.

My factory rears just pressed back in.

Did you check the bores when you had the pistons out?

This was with caliper removed from the car, and without hose. Bleeder was probably shut but that shouldn't matter. I didn't remove the pistons yet. I bet they look like hell after 30 years though. The wilwoods I could compress by hand.

I'm just gonna order reman ones from Centric. Its not clear but it looks like they put in new pistons, they mfr them at least, so that's a good sign vs reconditioned ones I think, and the calipers should have SS sleeves vs OEM that doesn't.

They are out of stock on the left rear, but they have one still for the 84 with pads and bracket. The only difference between 84 and 85 there is the bracket. The new pads will probably go right in the trash.

I just remembered I have a pair of 88 rear calipers I could test in comparison.

Quote:

I have an offensive answer though, what does the MC cap have to do with anything?

Quote:

Because nowhere in your first post did you say the calipers were off the car.

hit a motorcycle junkyard & get a MC use that and a hose to press them out

Quote:

Even if they were on the car, I don't understand the reason for the question.

Probably a stupid question but did you try soaking them? Sometimes that's all they need to free them up.

Quote:

If the caliper is on the car, removing the master cylinder cap makes it easier to compress the piston so you are not trying to compress the fluid in the system. Some people will crack the bleeder screw instead.

if you didn't already solve this, you can have my C4 rear calipers. Just pay the shipping.

They worked fine when I took them off, but they've been sitting for five years. There may even be SS lines on them but I can't remember.

Too late, remans are in the mail. Honestly can't expect much from dissimilar metals 30 years old in hydroscopic fluid trying to stay free moving and also maintain a seal to hold in 1000+ psi of pressure.

Yeah, it's kind of funny. I would say the majority of us at the very least do our own brake jobs, but until recently I never gave the caliper itself a second look. Now I disassemble, inspect, and clean them regularly. It's so simple I don't know why never did before.

People overlooked the pins on the sliding calipers

Check the groves on the slides
They wear out.
They make oversized pins to compensate.

I like shiny parts. One of these is from an 84 caliper setup, they come powder coated which is strange. I painted the other gloss black to match and cleaned up one of my brackets to reuse. New pistons, seals, pins, hardware. Centric provides nice clean brackets. Probably not many left on their shelves. The 84 unloaded caliper was no longer available on that side, and no more 85-87s. The anti rattle clips are stainless H shaped pieces that go in the pocket of the caliper where the pad springs press against. I guess it lets them slide easier if nothing else. The caliper pin holes are round, the pins have 3 flats which I assume are only there to hold lube in there.

I put in the earls bleeders. Haven't used them before but I like the design of it prevents sucking air in through the threads.

Attach file:

---

  image.jpg (562.11 KB)

Good to know that is where those h shaped pieces go.