Sticky rear caliper..... where to go from here

[TB99Max]

I noticed the inner piston was sticking on my rear caliper a few weeks ago. Ordered a new seal kit, put it in, and blew out the caliper with compressed air. Put it back together and still doesn't work! The pad is actually in contact with the rotor so that's obviously not good! Where should I go from here?? A new caliper?
Thanks guys

 

[TB99Max]

Also..... If buying a new caliper is what's recommended, is there a bolt on upgrade available?

 

[one2dmax]

Did you polish up the pistons and also clean up the bore? The pad should just barely retract from the rotor.

 

[Fire-medic]

As Sean said & when dry you sould be able to easily move the brake fluid lubricated pistons/seals in & out w/your fingers. you also might try cleaning your brake line and rear master cyl as a deteriorated line on the inside or a plugged/blocked hole in the rear master cyl could be causing the failure to retract. I once got a set of aftermarket pads that were too thick & I had to dress them slightly w/a belt sander to gain sufficient clearance. I thought that odd but I disassembled and blew out the rear master cyl & line twice, thinking it was related to the pistons sticking in the actuated position before I did that and no issues since. The pistons would retract enough to allow the bike to roll in neutral, but dragged while underway, enough to get the caliper really-hot. I had experience w/a partially-collapsing (internally) brake line before this on another vehicle, and the symptoms were similar.

 

[TB99Max]

I will take it apart again and give it another try. I thought about the rear master but one of the Pistons seem to work ok but definetly not able to move either one with my fingers.

 

[Fire-medic]

A way to free the piston, it requires total disassembly of the caliper to clean the pistons after freeing them. You can do it on the bike or on the bench to free the piston, but then you must disassemble the caliper to clean it. I suggest doing it on the bike to free the piston, then remove it to clean the caliper.

Disconnect the brake line to the piston, replace the hose fitting w/a properly-sized teflon wrapped bolt, insert the bolt until it hits the bottom of the bore but don't tighten it. Open the brake bleeder. Connect a grease gun to the brake bleeder, and fill the caliper w/grease. Your garden-variety manual-pump grease gun can generate probably 1500 psi + (cordless ones several times that!) which is far more than your compressor, if you have used a compressor to blow-out pistons before. I have never encountered a caliper/piston this wouldn't free.

Now you need to disassemble the pistons & caliper to clean the grease out, no big deal, a brake cleaner solvent can will make short work of this.

Carefully clean and reassemble the caliper & pistons, lube the square o-rings w/clean brake fluid before installing them. You should be able to easily slide in & out the pistons w/your fingers before re-uniting the caliper halves.

 

[TB99Max]

A way to free the piston, it requires total disassembly of the caliper to clean the pistons after freeing them. You can do it on the bike or on the bench to free the piston, but then you must disassemble the caliper to clean it. I suggest doing it on the bike to free the piston, then remove it to clean the caliper.

Disconnect the brake line to the piston, replace the hose fitting w/a properly-sized teflon wrapped bolt, insert the bolt until it hits the bottom of the bore but don't tighten it. Open the brake bleeder. Connect a grease gun to the brake bleeder, and fill the caliper w/grease. Your garden-variety manual-pump grease gun can generate probably 1500 psi + (cordless ones several times that!) which is far more than your compressor, if you have used a compressor to blow-out pistons before. I have never encountered a caliper/piston this wouldn't free.

Now you need to disassemble the pistons & caliper to clean the grease out, no big deal, a brake cleaner solvent can will make short work of this.

Carefully clean and reassemble the caliper & pistons, lube the square o-rings w/clean brake fluid before installing them. You should be able to easily slide in & out the pistons w/your fingers before re-uniting the caliper halves.

When I took it apart to put the new seals in I got the pistons out with my compressor (150 PSI) and thought I cleaned it good enough. I was thinking maybe something was in one of the passageways in the caliper body, so I was going to try to stick some thin wire through it and see what happens.

 

[Fire-medic]

See if you have any limitation on the flow thru the hose from the master cyl to the caliper. Blow both ways w/your compressed air. I've had deteriorated brake hoses on cars, trucks, and bikes. It can act like a 1-way valve instead of freely-allowing flow of brake fluid both ways as it should. Also try cleaning the master cyl if you haven't before.

When I took it apart to put the new seals in I got the pistons out with my compressor (150 PSI) and thought I cleaned it good enough. I was thinking maybe something was in one of the passageways in the caliper body, so I was going to try to stick some thin wire through it and see what happens.

 

[TB99Max]

The way everything has been on this bike.... I definitely wouldn't be surprised if it was gummed up! It lived most of its life close to the beach.

 

[Fire-medic]

Davesax recommends a guitar string for cleaning orifices, I think you could use an appropriately-sized one for the hose if you found it clogged, but you would have to be sure that once you used your 'ramrod' that the inner jacket of the hose wasn't damaged.

A bit of brake cleaner sprayed onto the guitar string and maybe a pair of pliers to feed it through whatever crud had blocked the passageway, flushing w/the brake cleaner really-well, and then reassembling & bleeding everything, and checking to make sure that the brake pressure released, allowing the pistons to retract, and not to have some internal collapse, causing a '1-way valve' effect, where the piston pressure wouldn't release, is in-order.

 

[jfeagins]

I will take it apart again and give it another try. I thought about the rear master but one of the Pistons seem to work ok but definetly not able to move either one with my fingers.

DO NOT FORGET to clean the grooves on the inside bore of the calipers, where the O-rings fit in. If those bores have grime buildup in them, it will cause the rubber rings to seat too firmly against the pistons, which can bind them enough to cause grief.

 

[Fire-medic]

I use a Dremel and a SS round wire brush, it cleans the groove nicely/quickly.

DO NOT FORGET to clean the grooves on the inside bore of the calipers, where the O-rings fit in. If those bores have grime buildup in them, it will cause the rubber rings to seat too firmly against the pistons, which can bind them enough to cause grief.

 

[TB99Max]

I'm going to pull it apart now and look over everything again. I'm working nights right now, its kind of nice to get paid to work on my Max!

 

[TB99Max]

Has anyone had any issues with aftermarket seal kits? I took everything apart the grove that the seals sit in are completely clean and the piston is still super tough to get in there. Once I put it in the only way I can get it out is with a compressor.

 

[Fire-medic]

Yeah, sounds like the manufacturing spec for the o-ring is too-tight. Get the stocker.

 

[one2dmax]

I use OEM parts for that sort of thing but never tried the aftermarket caliper kits to know for sure if they are good/bad.

 

[jfeagins]

The cup should be a rather snug fit inside the caliper upon correct reassembly. I use a tiny amount of oil, or fluid to reassemble, so's the cup will re-start past the rubbers without damaging anything. I'd think if it were loose enough to easily pull in and out with bare fingers, it would be loose enough to force brake fluid out while normal braking. Not sure how many PSI is involved when the brakes are applied, but I'd think it was significant to create braking pressure.

 

[Fire-medic]

Coat the o-ring in brake fluid and re-insert into the caliper groove, and then push into the caliper a piston also coated on its outside circumference w/brake fluid. It should smoothly insert, and you should be able to move the piston in and out using your fingers without any great effort or tool use. Likewise coat the dust seal lip where it contacts the piston w/brake fluid. Insert the dust seal 'dry' into its location.

Next time you're at the auto parts store, see how easily you can move the pistons on a caliper, brand-new. All you need is finger pressure.

 

[jfeagins]

Wouldn't that depend, entirely, upon whose finger it was? Mine are said to be much gentler than most. :biglaugh:

 

[Fire-medic]

Ok, ok, I surrender! You, like "Madge" must have 'soft hands' and that means your fingers are uncalloused and probably soaked nightly in dishwashing soap, or something.

http://articles.latimes.com/2004/feb/20/entertainment/et-stuever20


https://www.youtube.com/watch?feature=player_detailpage&v=B_xOg0SUAds

The answer to this issue I bet is to use OEM piston O-rings, wholly-dipped into brake fluid, and inserted into the caliper grooves, and then replacing the shiny, bright clean pistons, also coated on their outer circumference w/brake fluid. Then your pistons should slide into/out-of the bore, "like buttah! (Parkay!)"

Well, not so-easily that they would fall out on their own, but any caliper I've ever worked on, you could use your hand to push/pull the piston, and yes, there is friction there, but I didn't need to use some expanding hand wrench to clamp inside the piston to get it to budge. I may have given the wrong impression w/my remark about moving without using a tool, for the pistons.

Wouldn't that depend, entirely, upon whose finger it was? Mine are said to be much gentler than most. :biglaugh: