brake piston removal

[inchman]

hi all, im starting to overhaul a pair of rear calipers for my 90, has anybody any tips or hints for getting the old pistons out, btw, they have been sandblasted and sitting on the bench.

cheers gary

[western]

I used a footpump to blow the pistons out last time I had caliper off to replace seals.

[Tanuki]

Must admit, I've always worked on the principle that if you can't grab the edges of the pistons with a pair of soft-faced pliers and 'work' them out by hand then the thing to do is to hurl the offending caliper into the scrap-bin and fit new.

I can swap a front- or rear-caliper in 20 minutes.

Stripping/cleaning/rebuilding a crappy old caliper will add at least another half-hour to this - and often you don't get to realise the full internal horror of a corroded caliper until you get it apart - (add in the at-least-50% chance that the bleed-nipple of the old caliper won't come out cleanly) - which then leaves you with a Vehicle-Off-Road.

Swapping in a new caliper is cheapest!

[Ibex94]

Similar to Western, I welded two of the brake pipe tube nuts together screwed one end into my airline blower and the other into the calliper. Stick block of wood between pistons so they don't pop out until you've got them all out.

Simples

Rob

[SvBeek]

If it doesn't work using air, I used this method last week:

split the caliber parts (makes fitting new seals a lot easier anyway). Carefully drill a hole in the stuck piston. Tap a thread into the hole. Put a bolt in, and pull out the piston using the bolt as an anchor

[duncmc]

When I rebuilt my front calipers, I had trouble too. I split the calipers, and used a vice to hold the piston, whilst trying to turn the caliper.

[Snagger]

I leave the calliper in place with the pads removed, then pump the pedal hard to push the pitons out part way. Wiggle the calliper a bit once disconnected and unbolted to ease the pistons a tad, then remove the calliper, split it and use the vice or mole grips to get the pistons the rest of the way out.

Make sure the seats for the seals are spotlessly clean and file the edges of the retaining rings to make insertion easier. I found it easiest to fit the pistons before the outer seal and retaining ring, so the piston centralises them.

[Spearos]

I had this exact problem last week. Some good suggestions there, especially like the idea of drilling/tapping the piston and using a bolt - great idea!

The way I did it though was to split the calipers, leave some plus gas to soak in on the offending seized pistons before gripping them with water pump pliers and twisting them. Once the 'seal' was broken they popped out nicely with compressed air.

Another option would be to use a punch and hammer to try and and get the pistons turning in their bores, once they're moving it shouldn't be too hard to get them out.

It all depends I guess on the condition of your pistons, and if you plan to replace them?

Don't ignore what snagger says above, I made sure the seats for the seals were spotless with small bits of Scotchpad and had no trouble what-so-ever getting the retaining rings in.

HTH

[Snagger]

It all depends I guess on the condition of your pistons, and if you plan to replace them?

Rule of thumb is that if you're having to pull the pistons out, they need replacing anyway, but if you use grips or a vice without rubber jaw pads, you'll have to replace the pistons as the old ones will be damaged in the withdrawl.

I have Zeus stainless pistons in all callipers on my RRC and 109 (disc conversion) and they're great - well worth the money to get a kit from them, though you might want to consider getting genuine seal kit as Zeus supply pattern kits with their pistons. I used their kit and have had no problems other than fitting the outer seal retainers - they aren't as well made as the genuine retainers and tend to pick up and bend on fitting. They're the hardest part of the job by far.

[inchman]

hi all, thanks for the advice, im using new bearmach pistons and seals, and they're not shifting with 90 psi,

so think ill split them and drill and tap.

cheers gary

[Snagger]

I'd connect them back up to the vehicle - the master cylinder puts out much, much more than 90psi!

[Frax]

Another one to try. remove the brake bleed nipple and fit a grease nipple - then use a grease gun to pump the piston out.

Waste's quite a bit of grease but has never failed me. You obviously need to give the calliper a good clean out afterwards but worth a go.

[Snagger]

That should work, but could blow a cheap grease gun apart. You have the vehicle hydraulics sitting there, and they're the easiest way. You don't need to worry about proper bleeding to do it as you can just pump the pedal.