pistons stuck in caliper!!

C

chris varming

Member
Gentlemen - I'm about to renovate two front brake calipers for the P6 - they have been stored for about 5 years and not surprisingly the pistons are stuck in the caliper body. It's no use blowing them out with compressor. How do I get them out? Violence?? any suggestions gentlemen??? regards, Chris Varming
 
Hi Chris,

I am assuming that you have released the bleed screw, attached a hose and that air pressure will not shift any of them,..is that correct?

If there is a fair amount of corrosion between the piston and the bore, then they could well be effectively welded in there. You could send them to England as an exchange pair in return for a refurbished pair... :?
The place that then overhauls them may well separate the two halves I imagine and mill out the offending pistons. I don't know if this is possible, just thinking aloud.

Ron.
 
I've heard a grease gun can work to press the pistons out, but it all has to be very carefully cleaned afterwards.
 
Probably the best way to get pressure into them is to connect them to a brake system, far more pressure than an air line can produce. Also worth spraying some wd40 around the pistons, and applying a little heat (not too much) might help to break the rust seal.
 
I loosened a seized rear piston by using Harveys trick, fill the gallery with fluid, cap with bleed nipples, and heat. It didn't appear to make a noticable difference at first, then I reapplied a footpump to it, and the piston moved.


John.
 
^^^^webmaster

That's how I did it. Stick the bleed nipple back in, connected it back up to the car by the hose (didn't mount it). Stuck a 1/2 in bit of wood where the disc would go, took away the pads and got a friend to pump the pedal. The pistons moved out until hitting the wood, allowing them to be jiggled out the remaining 1/4 in. If you don't put the plank in, the least seized pot comes clean out spraying fluid everywhere, and the other remains totally stuck. You have to get them out simultaneously.

Michael
 
Thanks all for your advice - I'll try to reconnect the caliper to the braking system of the car as suggested and see what happens - I*ll let you know if it works or if I shall send them to GB (any speciffic company you can reccomend Ron?) - regards, Chris Varming
 
Chris,
I managed to get the large pistons ouf of mine with compressed air, when reinserted it an clamped it so that the force was applied to the other pistons. However, dispite working them in and out (they moved a bit) over and over they wouldn't budge. Eventually we had to resort to welding bits of scrap to each piston in turn (see here - viewtopic.php?f=21&t=9929) and hammering them out. I had already ordered 6 new pistons and new seals so I wasn't concerned about saving the old ones, and to be honest, if they are that badly seized they could already be scrap. If the bores are ok the cost of parts and delivery of the postons/seals will work out far cheaper.
Regards,
Dave
 
Chris.

as suggested by Sindneyroverp6 - a sucessful method i have used in the past is to soak the piston areas in WD40 for a day or so, then connect a grease gun hose to the caliper port and pump the grease gun until the handle cannot be moved, using quite a lot of force. The hydraulic force of the grease should force it out. Applying a BIT of heat with a hot air gun whilst under pressure may also help. Wear safety goggles for this operation, in case a pipe splits etc. Be careful, as when the piston does let go, it may do so with a bang and a spurt of high pressure grease.

Glen.
 
... and don't have it pointing towards your mother-in-law's car. I did that once with a stubborn clutch slave cylinder while she was visiting, then had to spend half an hour washing all the brake fluid off her paintwork.
 
In the past, not having access to a compressor or having thought about reconnecting the calipers to the brake lines, I levered the pistons out using a pair of flat-headed screwdrivers that fit in the groove where the dust seal sits. There's quite a risk that the collar will get bent, of course, but if you're going to fit new pistons to the calipers this could be an easier fix? It worked for me.
 
You must log in or register to reply here.
Back
Top