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Hi Peter In your caliper rebuild faq you say to soak the pistons and calipers in solvent as long as possible. Did you mean to immerse the entire caliper in solvent? Thx Karl

From rebuilding Kart calipers and my own 528's: I was amazed the rebuild kits don't include the little black rubber O ring to replace the oldie, between the two caliper halves. That's what seals the transfer passage between the two. Because I went about taking everything apart same as all the kart calipers, I had to reuse the old one. The thing is so teeny I doubt there's much danger of them going bad, but that's the reason it's naughty to split the calipers.

Far as I know the calipers work on a simple principle: pushing the pedal forces fluid through the lines. As it can't go anywhere, the stuff pushed by the master cylinder piston goes into the calipers, little tunnels, behind the pistons and pushes them out, to pinch the rotors.

Age, rust, crud and water in the brake fluid work to mess up the nice clean lines and tunnels. The object of the rebuild is to clean all that out, by sloshing, dipping, steel wool, fine, fine sanding. I.e., don't skin up the smooth gasket, O ring surfaces to cause leaks.

Odds are the tunnels in the calipers aren't totally plugged or even plugged at all. If so you'd have large hints with stuck pistons or funny brake behavior. A good rust remover is toilet bowl cleaner that says so on the label.( The right stuff foams while eating.) Do rinse everything with soapy, then clean water and dry completely with an air gun.

If you haven't removed them yet, absolutely buy the Napa brake fitting vice grips. Don't argue, do it. The 7mm six sided box wrench with one side cut out is fine for assembly, but a neat way to booger fittings that are even slightly stubborn stuck.

To get the pads away from the rotors, open the bleeders and stick a fat screwdriver between the pad and rotor. Remove the pads, close the bleeders and use the pedal to push the pistons out, close to the rotor. Object is saving yourself the aggravation of trying to grab, pull the pistons out from deep in the caliper on the bench.

The allen bolts on mine were rust crunchy, needed removal and cleaning. If the fear of the teeny O ring makes you leave the calipers together, I say take the assembly bolts out one at a time, clean and return.

Somewhere convenient in the process I highly recommend primer, painting the calipers with high temp engine paint. Tape off the pistons, etc. The old calipers will probably have shed any protective coating, rebuilts look great for about a month, then turn glorious rust film. Unless you don't care what Gophers think running around under your car.

Use brake fluid (DOT 4) to lube the piston, O ring, cylinder. Push it straight in, which is more difficult with the two halves together.

Bleeder fittings aim up. I've had better luck installing the brake line fittings before bolting the calipers back on, but all that counts is feeling the threads are happy turning in and the fitting isn't cocked inside for compression.

A pressure bleeder is the cat's pajamas for proceeding without waiting on a friend. Bleed from the caliper furthest from the reservoir. All bolts, fittings tight ( snug plus a quarter turn.) Wipe off brake fluid as it eats paint.

If the pedal isn't firm, pretty close to the top, you can bleed again or ask how to check the under dash set up of levers.

Thanks for all the tips on doing this procedure. Makes sense to use the toilet bowl cleaner and water instead of solvent? I wasn't planning on splitting the calipers so one concern I had was that if I soaked the caliper in solvent I might ruin that little "o' ring. (was there a torque value for reassembly of the halfs?) I like your idea of installing the brake line fittings before attaching the calipers...gives you a bit more wiggle room to line them up properly so you don't cross thread the fitting.

Mike W. has his own torque wrist, vs. wrench. For the bolts missing from the charts, and there are many, I use a close guess from like parts, bolt diameters, materials. As the calipers and bolts are steel, snug plus a quarter turn. Mostly the idea of feeling tight without stripping the threads being silly.

Toilet bowl cleaner is some kind of not too nasty acid. Sure works good for the old hardware, save it does eat the zinc plating. I've used it to loosen bolts instead of the autoparts aerosol squirt cans.

canada karl wrote:Thanks for all the tips on doing this procedure. Makes sense to use the toilet bowl cleaner and water instead of solvent? I wasn't planning on splitting the calipers so one concern I had was that if I soaked the caliper in solvent I might ruin that little "o' ring. (was there a torque value for reassembly of the halfs?) I like your idea of installing the brake line fittings before attaching the calipers...gives you a bit more wiggle room to line them up properly so you don't cross thread the fitting.

I'd just use brake cleaner. It won't hurt the o ring