Topic: replaced piston seal and still got problems!

[1884dale]

i replaced the piston seal in the caliper Friday and still have a sticking issue.  was going to rebuild the master cylinder now but don't know how to get it apart  also wondering if i should replace the hose first
any input would be appreciated!

[robe0531]

i think but not 100% sure but to take the master apart i think u need to look down where the banjo bolt goes there should be a clip that u need special pair of needle nose to get out and that should take it apart

[Gordon]

Did you clean out the seal groove really well before putting in the new seal?  Does the brake pad slide in and out of the housing easily?  Some after market pads are just a tiny bit too big and bind in the housing. 

[r6100mph]

Did you just replace the seal in the caliper?  If so, you may need to scrape all the debris from around the cylinder where the seal sits.  The build up of debris around the seal doesn't allow the piston to retract.  it could be possible that your seal was fine.  just my 2 cents

[Inigo Montoya]

Others have mentioned it. You need to clean the WHOLE caliper inside. White crud builds up because of the water absorbing nature of DOT3 fluid. Easiest way is to use a brass wire wheel on a dremel and go to town all over the sides and in the seal groove. I know when eyeballing the housing, it never looks like much is in there but then when you actually clean it, a lot really does come out and it takes very little bind things up.

It maybe possible that your master is dirty too. There is a small return hole and it can clog easily. A circlip pliers will make removing the clip easy bit an angled pick will work too.

[1884dale]

Did you clean out the seal groove really well before putting in the new seal?  Does the brake pad slide in and out of the housing easily?  Some after market pads are just a tiny bit too big and bind in the housing. 

i used 1000 grit sand paper and i sanded the whole caliper housing.  the old seal look good still, but i replaced it.  i used brake cleaner and sprayed  out all the dust.  what could i do about the pads being to big, grind them down?  that actually sounds like the problem.  they seem to "bind"  i put some brake grease on the outside ( a very small amount) of the pads to try to get them to slide, but that doesn't seem to do anything.  when i try to bleed the brakes, the pad will close in around the rotor but won't release.  btw, the piston looked new, no pits at all

[Johnny5]

My brake was sticking last year and I broke down the caliper, cleaned out the piston, didnt change the seal, but cleaned the groove with sandpaper and lubed it up with some brake grease. Works great and no dragging. Did you lube the piston seal?

[bryanj]

From what you say you did not clean out the seal groove enough

[Bob Wessner]

I tend to agree. The groove has to be cleaned well in the corners, all the way around.. both sides. I used a dental pick.

[Inigo Montoya]

That groove is what gets everyone the first time.

[1884dale]

ok, i'll take it out and clean it better, but i did scrape it out with a small flat screwdriver ( i don't think i mentioned that)  i do have to clean out the master cylinder better and the little holes still.  you know, i could get alot more done on my projects if i didn't have to keep going to work.  i drive a truck and have NO schedule.  anyway, i'll stop complaining, thanks for all the feed back! 

btw, what about the pads being a little bigger than oem?  how do i go about fixing that?

[Sweep]

Imagine you're a dentist and that groove is teeth from a non brusher.  I had to do it twice too.  When my pick stopped pulling up any gook I knew I was done.  You will be able to push the piston in easily and it should spill out when turned upside down.

[1884dale]

really!   that loose?  piston should fall out?   i have more work to do then

[ev0lve]

Did you clean out the seal groove really well before putting in the new seal?  Does the brake pad slide in and out of the housing easily?  Some after market pads are just a tiny bit too big and bind in the housing. 

i used 1000 grit sand paper and i sanded the whole caliper housing.  the old seal look good still, but i replaced it.  i used brake cleaner and sprayed  out all the dust.  what could i do about the pads being to big, grind them down?  that actually sounds like the problem.  they seem to "bind"  i put some brake grease on the outside ( a very small amount) of the pads to try to get them to slide, but that doesn't seem to do anything.  when i try to bleed the brakes, the pad will close in around the rotor but won't release.  btw, the piston looked new, no pits at all

Is the puck brown? Had a set and had to take the paint off the sides for it to move right in the caliper.

[bryanj]

2nd thought, have you checked the pivot pin arm to bracket, needs to be very free

[1884dale]

2nd thought, have you checked the pivot pin arm to bracket, needs to be very free

i don't know what the pivot pin arm is so probably not    hopfully i'll have some time to check it out wednesday    thanks again for any thoughts,  keep'em comin!

[bryanj]

The caliper bolts to an alloy bracket with 2 bolts, this bracket pivots on a steel pin and must swing freely without sticking anywhere

[1884dale]

The caliper bolts to an alloy bracket with 2 bolts, this bracket pivots on a steel pin and must swing freely without sticking anywhere

is this the arm that has a bolt with a spring so you can adjust the "back/non moving" pad?   if so, i just found out about that adjustment and haven't really messed with it, but i think that it is in need of adjustment.  i put new pads on the bike when i got it and didn't adjust it

[TwoTired]

There is a brake caliper rebuild walk-though in the FAQ

[bryanj]

Yes it is, take the adjuster bolt right out along with the spring and the arm should move easily

[Inigo Montoya]

You will most likely need to pull the bolt out and clean it up and lightly grease it. once you put the pad back in, there should be a gap of something like .008 between the pad and rotor.