godzilla Posted April 9, 2008 Report Share Posted April 9, 2008 The pistons in my front ajp 4 pot caliper could do with changeing, has anyone done this? i know you can get a kit but how easy is it to do, and how do you actualy get them out? please help as i cant afford a new caliper! Quote Link to comment Share on other sites More sharing options...
sectionone Posted April 9, 2008 Report Share Posted April 9, 2008 I've never taken the pistons out of the 4 pots but have done it on the 2 pots. Take caliper apart and put a rag over the pistons and use compressed air to pop pistons out. Check the rubber seals as it only may need replacing, not the piston. Unless you have fluid leaking on your pads, your problem may be elsewhere like the master cylinder. I think a piston going bad is rare. Quote Link to comment Share on other sites More sharing options...
godzilla Posted April 9, 2008 Author Report Share Posted April 9, 2008 The problem is the pistons wont go back in so i casn put new pads in. they are corroded Quote Link to comment Share on other sites More sharing options...
sectionone Posted April 9, 2008 Report Share Posted April 9, 2008 Is the cylinder corroded as well? If it is, you probably need a whole new caliper. Try taking the rubber seals off and putting the pistons back in. If you can do that, swollen seals are making the pistons not go back in. Quote Link to comment Share on other sites More sharing options...
godzilla Posted April 9, 2008 Author Report Share Posted April 9, 2008 The piston is corroded not sure about the cylinder as i dont want to take it apart if i cant get it back together. it works but there is only a couple of mm on the pad and they will need changeing within a couple of trials. would you remove the piston to inspect the cylinder? Quote Link to comment Share on other sites More sharing options...
mad4it Posted April 9, 2008 Report Share Posted April 9, 2008 Split the caliper halves ,remove the bleed nipple from the opposite half to the banjo bolt side place piston side down on a bench and blow them out using conpressed air pop out the seals fit new seals and pistons and re assemble job done. half an hour job! Quote Link to comment Share on other sites More sharing options...
godzilla Posted April 10, 2008 Author Report Share Posted April 10, 2008 split into symmetrical halves? will it seal back ok the kit only has seals for the pots and a small o'ring.. Quote Link to comment Share on other sites More sharing options...
alan bechard Posted April 10, 2008 Report Share Posted April 10, 2008 split into symmetrical halves? will it seal back ok the kit only has seals for the pots and a small o'ring.. That small o-ring is what seals the two halves together. Take it apart, clean exceptionally well with scotchbrite or some form of scrubby pad that will not scratch, use brake fluid as a cleaning lubricant, lube o-rings and seals with clean brake fluid and re-assemble. Bleed and you should be good to go. Quote Link to comment Share on other sites More sharing options...
02-apr Posted April 10, 2008 Report Share Posted April 10, 2008 That small o-ring is what seals the two halves together.Take it apart, clean exceptionally well with scotchbrite or some form of scrubby pad that will not scratch, use brake fluid as a cleaning lubricant, lube o-rings and seals with clean brake fluid and re-assemble. Bleed and you should be good to go. Before putting the pads back, spray the pistons with silicon spray which stops the dirt geting a hold, lubricates the rubber safely and prevents corrosion if subsequently kept clean and retreated at intervals. Like most folk I don't have compressed air but polished the pistons with a toothbrush and Belgom Alu, a non-abrasive polish, before pushing back in and doing the above. Quote Link to comment Share on other sites More sharing options...
alan bechard Posted April 11, 2008 Report Share Posted April 11, 2008 Before putting the pads back, spray the pistons with silicon spray which stops the dirt geting a hold, lubricates the rubber safely and prevents corrosion if subsequently kept clean and retreated at intervals.Like most folk I don't have compressed air but polished the pistons with a toothbrush and Belgom Alu, a non-abrasive polish, before pushing back in and doing the above. I would advise caution at using ANY cleaning agent besides the fluid intended for those parts. Elbow grease will not react badly with any of the seals. As the gentleman above said, many silicone sprays are fine, but do you really know which one is not? Some seals used in brake systems do not play well with some chemicals, so use other chemicals and sprays with the knowledge that things can go wrong, and at the least, try it on the old seals and check for immediate reactions. Quote Link to comment Share on other sites More sharing options...
neo Posted April 14, 2008 Report Share Posted April 14, 2008 My advice....from my own experience....if there's any corrosion at all anywhere......you can stuff around until your blue in the face. But the problem will always come back within a few weeks. Throw it away and buy a new calliper .....these are brakes....it's just not worth the hassle or the risk. Best of balance. Neo Quote Link to comment Share on other sites More sharing options...
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