Caliper piston popped out

[ZackDaniels]

I was installing my new brake pads and taking the opportunity to can-o-air out all the brake dust and what not while I was at it.

On the front left brake I noticed one piston was a lot more recessed than the other 3, and grabbed a 1x4 to slide into the middle to be sure the pistons didn't touch each other and clamp tight with no easy way to pry them free again. Worked the brake a couple of times and then pushed the working pistons back in. Rinse. Repeat a handful of times.

The stuck piston finally started moving out but as I worked one of the remaining 3 back into the caliper... a different piston popped out a bit too far from the back pressure and spilled brake fluid all over.

Obviously a bleed/fill is now an order... and I still need to work that sticky piston a couple of times. This is a first for me and it's the 4th time doing this with a brake shoe. Should I be checking any seals or doing anything else special as a result of this?

 

[ZackDaniels]

Also while I'm at it.

Retaining pin (2) - to lube or not to lube? If to lube then with what to lube?

For previous bikes I would put a bit of this silicone grease on the pins. Nothing in the Yamaha service manual says anything about lubing anything beyond dot 3 or 4 brake fluid though.

For that matter, what's the consensus on using it or something like it to lube the back plate of the brake pads?

 

[Fire-medic]

It sounds as though you need to remove the caliper & disassemble it to clean the pistons & the body. You can usually re-use the seals after a good cleaning, but if the wide outer seal, the dust seal is deteriorated, replace it/them. A good brand of brake cleaner in a spray can is OK, but be-sure to wear eye protection when you spray-clean the parts & use compressed air to blow-dry the pieces.

I have used a grease gun before to free a stuck piston. SInce you're going to disassemble the caliper anyway, it doesn't make any difference about the grease being injected via a grease gun into the caliper. Last time I used this was on my Lake Orion, MI friend's CBR600 F2, we couldn't get one piston to move using compressed air or the brake fluid, but a few squirts w/a grease gun into the bleeder nipple, and that stuck piston came right-out.

I often use a Dremel to clean the corrosion, using a variety of brushes to clean all traces of corrosion from the caliper body and pistons, including a flapper wheel. Clean everything well, use a bit of brake fluid on the square inner o-ring, and you should be able to hand-assemble the calipers' pistons individually back-into the caliper body, no c-clamp required. Be sure the square-profile o-ring land in the caliper body has absolutely no signs of any corrosion before reassembly.

It's no big deal to disassemble a caliper for cleaning, but make sure you torque the screws to their correct value, and a bit of thread locker is in-order.

To disclose the factory manual's instructions, it says, "never loosen the bridge bolts." Those are the bolts holding the caliper halves together. Whether or not you want to do my method is up to you, if you feel uneasy about it, then take the calipers to your shop after dismounting them and let them work on the calipers for you and give them back to you ready for placement back-onto the fork legs and bleeding.

For the pins the pads slide-on, just clean them well w/a wire wheel, sandpaper, or whatever you need. I have never used any grease on them. For the back of the pads, if they squeal you can use some of the brake pad goo to stop them from vibrating, but that's the function of the thin stainless shims. The manual says, install the pad springs w/the longer side in the direction of the wheel rotation. You will see one side of the shim has a wider width than the other, as they sit on the top of the pads, see the manual for an illustration.

 

[ZackDaniels]

I reeeeeeally don't want to get into the whole caliper right now. I have limited time and a big ride on Sunday. Tight schedules and brake jobs don't mix well.

There's no visible corrosion, pitting, etc on the pistons... just a ton of brake dust. I was slowly working it out with success and was going to give it a scrub and rub it down with DOT 4. I'm pretty sure that and working it a bit is all it's going to take to get all 4 pots working together as they should.

The piston didn't pop all the way out either - just enough to puke fluid and let air in requiring a bleed. I slid it back in immediately. It didn't hit the ground so no dust or foreign matter should have been able to find its way in.

Do you still think the full caliper tear down/rebuild is necessary?

For the pins the pads slide-on, just clean them well w/a wire wheel, sandpaper, or whatever you need. I have never used any grease on them. For the back of the pads, if they squeal you can use some of the brake pad goo to stop them from vibrating, but that's the function of the thin stainless shims. The manual says, install the pad springs w/the longer side in the direction of the wheel rotation. You will see one side of the shim has a wider width than the other, as they sit on the top of the pads, see the manual for an illustration.

I've got a dremel and a wire wheel to match. I've also got some 000 grit steel wool pads I can go to town with. I'll go with that for now. Within the next year or so I'll be replacing all the lines with stainless steel and reconsider lube if there's any fight to getting the pins out again. I'll also take this opportunity to do a full caliper rebuild unless the consensus is it really should get done now. I saw the shims suggested in the manual but there are none to be found. As far as I know I'm the first person to be into the calipers and I thought they came stock?

 

[one2dmax]

just clean/polish the piston that came out. Make sure the bore is clean where the piston came out. Then reinstall.

Sean

 

[88vmx12]

just clean/polish the piston that came out. Make sure the bore is clean where the piston came out. Then reinstall.

Sean

Tah Daaah! :clapping:

 

[ZackDaniels]

That was the plan/is already done. Just figured I would ask if I should be looking at anything else since this was rather unexpected.

Thanks guys.

 

[ZackDaniels]

UPDATE:

So I bled the system and was surprised it only took maybe 5 minutes before it was completely bled out. I only bled from the caliper that had the problem but there's good pressure on front and rear.

I went EBC HH grade pads on both front/rear and wow.... what a difference in stopping power.

My new problem is in the rear - the new pad seems to be dragging ever so slightly, and while it's not squealing after a 10 minute ride I touched the rear rotor and it was very very hot. Should I bleed the rear out as well maybe?

Any other thoughts on what to check on why that might be dragging?

 

[Fire-medic]

I think you have a piece of grit on the small master cyl hole which is keeping the pressure on the line instead of allowing it to release when you remove pressure on the brake pedal. If you aren't careful, you could end-up bluing the rotor from overheating, and maybe glaze the pads. That would be an extreme case, and you might actually get the rear brake to come-on & not release, just what you don't want turning left at an intersection!

 

[ZackDaniels]

Ok forgive this noobery but the master cyl is on the bars and controls all 3 right?

Why would that only cause the rear to hold a little tight, and also how best to resolve?

:UPDATE:
I bled the rear and got straight fluid immediately.... not so much as a tiny bubble. So it's not air in the system.

I rode the bike for another 10 min braking as usual opposed to my previous 10 minute 'lets see how these new pads work' ride. The rotor wasn't so hot... there's for sure a bit of drag on it as I can hear it scraping when pushing the bike around off and in neutral. With the tire in the air on the center stand I get about half a rotation with a reasonable push. I know there's still all kinds of stuff hooked up, that minor drag is normal, and spinning free and clear isn't expected, but I would expect a full rotation or two with minimal effort?

It was only mildy warm to the touch after the second ride while the fronts were cool, and post quick stopping/locking tire tests the fronts were cool too while the rear was piping hot.

I use both brakes every stop so you would think the fronts would heat up quicker since they're doing most the work. I don't think this is normal, but maybe not as bad as originally thought.

 

[[email protected]]

Ok forgive this noobery but the master cyl is on the bars and controls all 3 right?

Why would that only cause the rear to hold a little tight, and also how best to resolve?

The rear brake has its own master cylinder connected directly to the rear brake pedal. The fluid reservoir for the rear brake is behind the right side cover (the one with the vmax logo) you may want to check fluid level since you bled the brakes.

FM is suggesting one of the ports in the master may be plugged. That is possible though you usually have symptoms much worse than you describe if this is the issue.

Another possibility is that the caliper needs a good cleaning. Sometimes cleaning the crud off the piston and from the seals will let the pads retract a bit easier.

Just note that the vmax wheel has a lot of drag on it having to turn the differential, drive shaft, output shaft,and middle gear assy when you rotate the wheel by hand.

 

[Fire-medic]

I had crud in the small hole of the rear master cyl for the rear brake that also allowed drag enough to get the disc v. hot. I ended up removing the rear master for a complete disassembly/ cleaning to be able to fix the problem. No internal bleeding experienced, no need to replace the piston/seals, just a thorough cleaning.

 

[ZackDaniels]

I cleaned and worked the caliper pistons when I swapped the pads. They seem fine. The only piston that was sticky was front left and that's fine now too.

I had no idea that separate reservoir and setup existed... and it has occurred to me that I've only had drum rears on every other bike I've owned until now.

Got the cover off, saw some nice dark amber crap in there (though the level was good), and bled/refreshed the fluid. I did this for the front a month ago and was under the mistaken impression that solved both front and rear. I feel pretty silly about not catching this in any time spent with the manual or just by common sense.

Put another 10 miles on braking as normal and I still hear a bit of a drag but the rotor hasn't heated up like that first time. It's still warmer to the touch than the fronts, but not hot.

Still no squealing, etc. just a gentle dragging sound... and there's supposed to be minimal contact with disk brakes right? I'm starting to think this is fine? The hot rotor was just a result of repeated quick stops, maybe?

 

[ZackDaniels]

:UPDATE:
They're fine and I was either I was overreacting to how hot the rotors got as a result of all the quick stops or the bleed on the rear took care of it.

Went for 20 miles on the highway tonight and got off then touched the rotors. They were fine. If there were any abnormal drag on that many miles at those speeds would have been at pretty toasty I would think.

They squeal a bit when coming to a complete stop, but I understand that's fairly normal for new pads on old rotors until they bed in. It was also very humid tonight so probably a bit of moisture collecting on the rotor as well. Hitting toys for tots tomorrow with confidence in my braking ability.

 

[gamorg02]

:UPDATE:
They're fine and I was either I was overreacting to how hot the rotors got as a result of all the quick stops or the bleed on the rear took care of it.

Went for 20 miles on the highway tonight and got off then touched the rotors. They were fine. If there were any abnormal drag on that many miles at those speeds would have been at pretty toasty I would think.

They squeal a bit when coming to a complete stop, but I understand that's fairly normal for new pads on old rotors until they bed in. It was also very humid tonight so probably a bit of moisture collecting on the rotor as well. Hitting toys for tots tomorrow with confidence in my braking ability.

should be pretty normal. like i said before if you still have a little squeal get in contact with morley about his 'stop squeal' stuff. it got rid of my squeal on the rear. its something that goes on the pad itself.

 

[ZackDaniels]

Thanks again for the pointer. I'm going to keep them dry and deal with it for at least the first few hundred miles to properly bed them in. If they're still chirping after the rotor gets that shiny look on it and the grooves line up I'll get the goop from Sean.

It seems it's only the rear that squeals when stopping. I'm starting to wonder if maybe the rotor isn't straight or something. Ah well I have all winter to mess with it now. They were just fine for roughly 100 miles on that ride yesterday and now the pressure is off so I can stop panicking and take my time with all of it.

 

[Redbone]

What is the accepted way to properly to bed the brakes? I normally do some controlled HARD braking from about 40-50 mph.

 

[gamorg02]

Thanks again for the pointer. I'm going to keep them dry and deal with it for at least the first few hundred miles to properly bed them in. If they're still chirping after the rotor gets that shiny look on it and the grooves line up I'll get the goop from Sean.

It seems it's only the rear that squeals when stopping. I'm starting to wonder if maybe the rotor isn't straight or something. Ah well I have all winter to mess with it now. They were just fine for roughly 100 miles on that ride yesterday and now the pressure is off so I can stop panicking and take my time with all of it.

yea thats what mine did. under 10 mph.

What is the accepted way to properly to bed the brakes? I normally do some controlled HARD braking from about 40-50 mph.

i usually read the manf instructions.

 

[ZackDaniels]

What is the accepted way to properly to bed the brakes? I normally do some controlled HARD braking from about 40-50 mph.

Real answer is it's a bit different for each set of pads, rotors, and conditions. The end goal is the same, which is just to get the grooves in the rotors to match with the pads and resulting in the most possible surface area for contact.

For me I'm following the procedure EBC recommends for their pads on normal street conditions:
http://www.ebcbrakes.com/troubleshooting.shtml

Drive your vehicle steadily within the first 300-400 miles of road use only using the brakes violently in case of emergency. During this time use the brakes lightly and intermittently to achieve a matching between the pad and rotor which we call break in or bed in.
The speed with which perfect brake in will have occurred depends on how often the brakes are used. If you drive on a freeway or motorway and do not use your brakes for miles at a time, break in periods will be much longer. Using the brakes with caution during their early life will extend their wear life and greatly reduce the chances of rotor vibration or “shimmying” as it is known in the States. During the bed in time the pads will only contact the disc on a limited area until tiny irregularities in machining or misalignment of the pads against the rotor have been removed. You can easily see how far you have progressed with bedding in your new brakes by looking through the wheel spokes and evaluating pad contact. The rotor should look shiny and smooth across its surfaces from outside to inside in all areas of the rotor.

They have an entirely different procedure for bedding on the track, which if you're inclined to do 120mph on the street you can follow that instead. I'm not so I won't be following that one. The very first thing I did was throw this out the window for my test ride and brake hard a handful of times. I did this just to get an idea of where my stopping distance needed to be and that's more important to me than the fullest possible life of the pads. I'm of the opinion that one test ride to determine what this is won't effect the overall bed-in procedure, but I could be dead wrong on that.

When it gets down to it this topic can get as loud as any oil thread. It's one of those things that everybody has strong and different opinions on.

 

[Redbone]

Found this on EBC's website: http://www.ebcbrakes.com/motorcycle_brake/mcdvd.shtml