83 rear brake stuck, re-built both MC and caliper, what next?

I have an 83 Venture Royale and can't get my rear caliper to stop sticking. I lately bled the lines using a compressed-air powered vacuum bleeder. The brakes are more solid than they've ever been but the caliper won't stop sticking. I've tried 2 different calipers and rebuilt one of them, polished the pins, greased everything that could need it, everything is like new on the caliper -- or as "like new" as a 33 year old caliper can be. I also just rebuilt the rear master cylinder a few months back, took that back apart and put back together when I did the caliper just to make sure mc wasn't the issue. I took the slave apart too, saw no issues, cleaned it, put it back together. Everything is now cleaned and rebuilt but the problem persists. I haven't changed the brake line but it's a stainless line, at least 3 or 4 years old, maybe older (it was on the bike when I got it). One last thing, the caliper does release some and did before the rebuild too. When the brakes are applied the tire stops and can't be moved but when I take pressure off, the pistons don't retract far enough to keep the pads from rubbing. Although with the brake released I can spin the tire again. Has anyone seen this before or have any suggestions?

I have an 83 Venture Royale and can't get my rear caliper to stop sticking. I lately bled the lines using a compressed-air powered vacuum bleeder. The brakes are more solid than they've ever been but the caliper won't stop sticking. I've tried 2 different calipers and rebuilt one of them, polished the pins, greased everything that could need it, everything is like new on the caliper -- or as "like new" as a 33 year old caliper can be. I also just rebuilt the rear master cylinder a few months back, took that back apart and put back together when I did the caliper just to make sure mc wasn't the issue. I took the slave apart too, saw no issues, cleaned it, put it back together. Everything is now cleaned and rebuilt but the problem persists. I haven't changed the brake line but it's a stainless line, at least 3 or 4 years old, maybe older (it was on the bike when I got it). One last thing, the caliper does release some and did before the rebuild too. When the brakes are applied the tire stops and can't be moved but when I take pressure off, the pistons don't retract far enough to keep the pads from rubbing. Although with the brake released I can spin the tire again. Has anyone seen this before or have any suggestions?

I would start to suspect the line, but sounds like it's pretty new (relatively). What happens if you crack the bleeder screw while it's dragging? does it free up or continue to drag. It's the fastest way I know to isolate a brake caliper/WC from the master and lines and try to narrow down the problem. Does yours still have linked brakes with a proportioning valve for the rear?

The flexible brake lines on autos anyway sometimes go bad in that the inside lining of the brake line collapses when the brake pedal/lever is released so that when the MC piston is pulled back by its spring pulling a slight vacuum on the brake line the line collapses instead of the vacuum pulling the caliper piston back. This could be your problem. Don't know.

The flexible brake lines on autos anyway sometimes go bad in that the inside lining of the brake line collapses when the brake pedal/lever is released so that when the MC piston is pulled back by its spring pulling a slight vacuum on the brake line the line collapses instead of the vacuum pulling the caliper piston back. This could be your problem. Don't know.

Exactly what he said. I hear the OEM brake lines will last forever but an aftermarket could be one from China. My experience with Chinese parts is they can start to deteriorate rather quickly.

It might be worthwhile to check and make sure the line is patent in both directions. I have yet to experience this on a bike but seen it on cars/trucks a handful of times. The line can act like a check valve r/t coming apart internally then cracking open the bleeder screw should release said pressure and reduce the amount of drag on the wheel. Then it could be the line or MC but it would rule out caliper if releasing fluid pressure via the bleeder causes the caliper to relax. I was not aware of a return vacuum created by releasing the brake lever, I thought the caliper piston return was handled by the piston seal, and the release of the lever slid the MC piston back opening up the fluid return port allowing that very minute amount of DOT3 to re-enter the MC reservoir (assuming the reservoir is not overfilled). I may have that wrong so someone with more experience than I may be able to give a more definitive answer on exactly how the pistons retract. IIRC pads will only retract around 0.004" in most hydraulic disc brake systems.

Exactly what he said. I hear the OEM brake lines will last forever but an aftermarket could be one from China. My experience with Chinese parts is they can start to deteriorate rather quickly.

 

It might be worthwhile to check and make sure the line is patent in both directions. I have yet to experience this on a bike but seen it on cars/trucks a handful of times. The line can act like a check valve r/t coming apart internally then cracking open the bleeder screw should release said pressure and reduce the amount of drag on the wheel. Then it could be the line or MC but it would rule out caliper if releasing fluid pressure via the bleeder causes the caliper to relax. I was not aware of a return vacuum created by releasing the brake lever, I thought the caliper piston return was handled by the piston seal, and the release of the lever slid the MC piston back opening up the fluid return port allowing that very minute amount of DOT3 to re-enter the MC reservoir (assuming the reservoir is not overfilled). I may have that wrong so someone with more experience than I may be able to give a more definitive answer on exactly how the pistons retract. IIRC pads will only retract around 0.004" in most hydraulic disc brake systems.

You are probably correct on the piston seal pulling the piston back. I'm not sure exactly how it all works but the fluid that pushes the piston out has to go somewhere for the piston to return to its resting place and the fluid returns to the MC when the MC piston is pulled back.

Thanks for all the help. I do have linked brakes and, as I just found out, I have a proportioning valve. I tried opening the bleeder, brake stays tight but I'm not totally dismissing it being the brake line, might replace it anyway. I think I can rule out the caliper being the issue. I have two different calipers, one of which I totally rebuilt. Both calipers do the exact same thing. I think Casey might be on to something though, I realized what I thought was a slave cylinder was actually a proportioning valve. I'm not sure what would make that valve have a problem but I took it apart when I did the caliper last week and put it back together, the one seal in there looked fine. It's raining here now but I'll try taking that valve off later and put the banjo straight onto the MC, see if that fixes it. If not I'll go get a new cheap piece of brake line. Will report results. Thanks again.

Thanks for all the help. I do have linked brakes and, as I just found out, I have a proportioning valve. I tried opening the bleeder, brake stays tight

 

If you open the rear caliper's bleeder and the caliper is still dragging, you have a caliper problem. When you open the bleeder all the pressure that could be in the line that connects the caliper to the master cylinder is relieved.

 

Frank

I'm a little late on this thread, but after reading the first couple of posts I was going to suggest looking at your proportioning valve. There's not a lot inside, pretty much just a spring and piston but the orifices could be blocked...

The function of the proportional valve is to cause a slight delay in the delivery of hydraulic fluid to the front brake when the rear brake pedal is pressed. The spring rate determines the time constant of the delay.

There is also a metering valve located near the front forks on the underside of the frame near the battery box. It is a simple orifice that regulates hydraulic flow to the front brake. How well is the one front brake working?? Wow, it's been a while, I think it is the right front that is linked to the rear, but if I am wrong somebody correct me...

Got to be a Dirty piston or plugged hole somewhere. With all you have done did you clean up pistons? Then it has to be a plugged orifice not releasing pressure.

Got to be a Dirty piston or plugged hole somewhere. With all you have done did you clean up pistons? Then it has to be a plugged orifice not releasing pressure.

I like steel wool in severe cases but a toothbrush and some solvent usually get pistons nice and clean. The inside of the bore has to be clean to. I have always used a hone stone on a drill but only when using new seals. One thing I recently learned is that I may be able to do this without installing new seals, guess I'll inspect and see.

If your pistons and bores are not nice and clean it could still be holding a slight bit. There is not much room for gunk in there and pads have only to barely move to release the rotor. It's normal to hear the pads touching the rotor when you give the wheel a nice spin, but it should still spin a few times before stopping.

Just a quick update (sorry if I'm stealing your thunder GR) - Golden Rider removed the brake line from the rear caliper to see how an R6 caliper would perform (just setting it on the rotor for testing purposes). The original caliper relaxed once the banjo was removed. Apparently, the problem is in the line or in the master cylinder. He is going to replace the line and make sure all the orifices are clean in the MC.

RR

There is a weee, tiny, very small hole in the master cylinder, on the side of the bore. If this sucker is plugged, problems such as you describe will be present.

There is a weee, tiny, very small hole in the master cylinder, on the side of the bore. If this sucker is plugged, problems such as you describe will be present.

Just a quick update (sorry if I'm stealing your thunder GR) - Golden Rider removed the brake line from the rear caliper to see how an R6 caliper would perform (just setting it on the rotor for testing purposes). The original caliper relaxed once the banjo was removed. Apparently, the problem is in the line or in the master cylinder. He is going to replace the line and make sure all the orifices are clean in the MC.

 

RR

Some testing to further isolate the blockage.

1) Crack the Banjo at the master to see if brake lets go.

2) Crack the Banjo at the caliper to see if brake lets go.

3) Crack the bleeder at the caliper to see if brake lets go.

There is a weee, tiny, very small hole in the master cylinder, on the side of the bore. If this sucker is plugged, problems such as you describe will be present.

Yeppers Goldie,, maybe take a quick read here: http://www.venturerider.org/forum/showthread.php?12536-Stranded-with-brakes-sticking-and-heating-up-Read-this

That Marcarl might be on to something!!

So it's been a little while since I wrote in here but I have been trying out everyone's suggestions and thanks to everyone for their help. As RedRider wrote the caliper did release when I unscrewed the bango bolt on the caliper, it doesn't release when I take it off the master or when I remove the bleeder, which would seem to point towards the line being the issue. One weird part though, I just put a new stainless line on today and the brakes still stick after I bled them.

After I put on the new line I took the L shaped piece off the master and cleaned the two holes in there by pushing a thin wire through it, still no luck. So now I'm trying to figure out what my next step should be. The caliper I think can be ruled out entirely, I have two 83 rear calipers at the moment (if anyone needs one let me know) and both do the same thing exactly, they stop the wheel then release only partially. I did rebuild one caliper with all new rings and both have newly cleaned and greased pistons. I also tried taking off the proportioning valve and connecting the line directly to the mc, it still stuck. All this, to me, points to the mc being the culprit. I did just rebuild the mc basically twice over the last six months but it's the only part I haven't replaced or routed around.

I'm pretty stumped here, also the linked front caliper doesn't seem to stick, I can hear the pads hitting the rotors when I spin the tire but it doesn't impede motion much. Is there some drag always on the rear caliper? I can still spin the wheel, it's just pretty hard and gets worse if I really stomp on the brake. I can drive it. I took it out for ten minutes today got it up to highway speed then came home(probably a 4 mile trip). I didn't notice much slowing or difficulty in accelerating (although I've been riding a KLR650 in the meantime so even severely depreciated acceleration would feel like a lot). The rear rotor was hotter than I think it should have been, especially since I used the front brake to stop with almost entirely, but it wasn't hot enough to sizzle if I put spit on my finger and touched it. Does anyone have any ideas what would be a good next step?

So,, a couple of thoughts. The first is that you mentioned small holes in the portioning valve, but I didn't see a mention of you approaching the small hole in the MC. This one, if plugged will cause a caliper hangup, but I think your problem maybe elsewhere.

When you re-built the caliper, did you use new seals? and did you perfectly clean the seal groves? Cleaning the seal grooves is a pain in the neck, time consuming job. Those grooves get loaded up with what could be described as hard-water deposits. Cleaning the one side is easy enough, but getting the side you can't see is a bugger. If the grooves aren't perfectly clean and you used new seals, the left over dirt will push the seal towards the piston and cause a drag. On the other hand, if you re-used the seals because they looked good enough, then the same may also happen because the seal is still being pushed towards the piston. I use a right-angled pick to clean the grooves and it will take upwards of an hour to do a good job.

I also thought about your comment that the caliper didn't release well enough when you opened the bleeder, but did when you loosen the banjo. This would indicate a dirty bleeder seat, or a plugged bleeder.

Hope this helps.

Thanks Marcarl, I actually did clean that little hole with a high E guitar string in the MC, I think I wrote proportion valve instead of MC on accident in my last post. I had the caliper on my kitchen table for about a week and spent time here and there with brillo pads, mechanics picks, and brake cleaner getting it spotless. I did use new seals and greased both the seals and the pistons with a fine film of the red rubber grease that came with my rebuild kit. I was pretty sick of the whole ordeal at the time and didn't want to leave any dangling 'what ifs' on the caliper if the rebuild didn't solve the problem.

One thing I haven't done is clean the reservoir. I didn't think about it until this minute but i took the mc back off and apart and am soaking the empty tube in carb cleaner. I am getting a bunch of dirt out of it. Now I just thoroughly cleaned this sucker twice in the last couple months so all this dirt is a surprise to me. I'm starting to suspect that maybe the reservoir, which has probably never been cleaned in 30 some years, might have some pretty heavy gunk in it which could easily clog one of the many little holes in the system. I'm going to take that off today, clean it and the rest of the system, put everything back together, and I'll post my results.

If that doesn't do it I'll be busting back open that caliper, just to make sure.

OK, I'm going to go out in left field here, but is there a possibility you have the spacer on the rear axle in the wrong position?? If that spacer is in the wrong place it will misalign the caliper with the rotor and cause binding...

OK, I'm going to go out in left field here, but is there a possibility you have the spacer on the rear axle in the wrong position?? If that spacer is in the wrong place it will misalign the caliper with the rotor and cause binding...

GOOD ONE BOB!!!!!!!!!:thumbsup::thumbsup:

Then again, it could be the spacer.

or a sticky pivot joint on the rear brake pedal that needs a little lube..

..or broken or missing pedal return spring...

or the little push rod that activates the master is adjusted to tight..

I'll jump in here for a little feedback. I also questioned the mechanical possibility of the brake pedal not returning correctly. It has been checked and there is a little play in it when at rest (like it should be). Also, pretty sure the wheel spacer is in there right. The rear wheel had not been removed from when the brakes were working correctly.

We are hoping the thorough cleaning of the reservoir will take care of this.

GR is in need of speed. The little KLR just isn't cuttin' it. Besides, spring break is coming up and I need something to ride out there. I'm tired of .

Keep it coming guys. You are really being very helpful. I'm not very versed on these old washing machines.

FYI - GR's bike is 6 years older than he is. Keeping the dream alive!

RR