Hi peeps,

I am in the process of changing my front discs and pads on the cos and have come up against a problem with the pistons. I have managed to push 3 of them in however one is not budging at all.

Does anyone have any advise on this?

I have read that people release the bleed valve and this should get it going, if I do this do I then have to bleed the system or just tighten up and add more fluid?

rgds

 

I would have at a guess that 1 of the pistons is siezed me personally would remove caliper, clamp your brake line so as not to lose brake fluid and then see if it will slide back if not it's time to take apart the caliper and fix the siezed piston if its old and worn i'd just go and buy a rebuild kit for both front calipers or some exchange units

 

if the piston is not budging, use plenty of wd40 etc on the piston, all around it and over it and everywhere else aruond the vicinity

then you the foot brake to try and push the piston out, after carefully arranging bits of metal to stop the other pistons coming out

you will ruin the pads and discs by coating them in wd40, but seeing as you are changing them in any case then it's a small price to pay

make sure you get a rebuild kit for when it's off so that you can clean the pistons up and do the general refurb of the calipers before they go back on again

not too sure what you'd do if the piston is scored though, as the new seals you put in might be damaged with the pitting or let fluid past

 

If they are the originals I'd seriously consider a new/recon pair, mine were around £50 each when I did mine.
If you want to try and pump the piston out, simply keep the old pads in the good side, and insert a spanner between disc and good piston to take up space and pump.
Don't be at all suprised if it doesn't work though, my set had 2 out of 8 pistons working, managed to free off another 4 after about 10 hours swearing etc, had to machine out the other two to paper thin then crush in, just not worth the hassle, I then discovered 2 stripped threads for the bleed nipples.
WD40 won't ruin discs simply clean off, diesel fuel works vastly better than WD40 though!!
tabetha