Please help me get my caliper pistons back in!

solihulls_finest

solihulls_finest

New Member
Had a go on the brakes a few days ago - I noticed the previous owner hadn't bothered with anti-squeal shims, so I ordered a set from Wins & co.

Problem is: With the pads removed from the left front caliper I've must've accidentally touched the brake pedal on the way out of the garage, so now the pistons are stuck too far out to put pads & shims back in! On the "engine side" I can just slip the pad in, but not the shim. On the "wheel side" the piston is 3 mm too far out to even fit just the old pad.

The weird thing is that both pistons are stuck - even with the bleed nipple and the fluid reservoir open I can't budge them! I've tried pressing them in with a piece of wood, but can only move them less than a millimeter. I tried pumping the brakes, but they don't suck back in. I should probably mention that all brake fluid has leaked away through my previous, faulty brake hose...

All brakes worked perfectly before - even pull and everything - before the brake hose burst. What do I do? Remove the whole caliper?
 
When you say "press them back in with a piece of wood" actually how much force are you using ?, they can sometime go back in with finger pressure but that is when brand new, normally they take much more force - I would use a long/strong metal lever such as a large screw driver say 18 inches long - perhaps you are being too gentle !

If the pistons have come out nearly all the way just make sure you are pressing them back in at 90 degrees to the caliper body, try and lever against the centre of the piston or 4 different points on the outer edge.

You can also buy special G clamp tools to push the pistons back in.
 
If there's no fluid in the system you could be pushing the pistons back in "dry" Try some brake fluid as lubricant
 
It sounds like your pistons are quite far out of their housings.
If your calipers are quite old you may be trying to force the seal over the unused and probably rusty/dirty section of the body that is not covered by the dust seal and when you do get it right you may well find the caliper leaking.
I would remove the pistons and give it all a good clean up and fit new piston seals and dust covers now, saving aggravation at a later date.
 
I always use a small "G" clamp. Fit it so that it makes contact with the piston and the body of the caliper. Wind the handle, carefully watching the piston to ensure that it remains straight relative to the bore. If you allow the piston to become crooked, it will be very much more difficult to move it... :shock:

Wind each piston back in turn. Ensure that the rubber boot engages with the lip around the edge of the piston.

What condition are the rubber boots in? Are they tired, hard and cracked?

Pistons over time, especially those used in a system where the brake fluid has not been changed at least every two to three years will suffer from pit corrosion, and usually this will be where the seals make contact with the piston. As such a proper seal is compromised and the caliper will leak brake fluid.

The only solution is to now fit new pistons, and of course a new seal kit.

Ron.
 
unstable load said:
It sounds like your pistons are quite far out of their housings.
If your calipers are quite old you may be trying to force the seal over the unused and probably rusty/dirty section of the body that is not covered by the dust seal and when you do get it right you may well find the caliper leaking.
I would remove the pistons and give it all a good clean up and fit new piston seals and dust covers now, saving aggravation at a later date.
Click to expand...

Well, I've got the previous guy's (I'll call him "the ancestor" from now on) receipts for new calipers from a few years ago, and the dust covers, pistons and what have you are all in excellent shape. Up till now I was afraid of damaging the discs if I pushed too hard with anything made out of metal...

Thanks for all the info guys, I'll invest in a clamp and bring my dad's cousin over - he used to service heavy machinery and has rebuilt more Volvo 123s and Beetles than I care to think about.
 
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