Rear Brake Problem

[brazos parker]

When I left for my volunteer job this am, both front and rear brakes worked fine (on a 2005 Gen I)...I have a steep, downhill driveway to test them on. I left the job around noon today and immediately hopped on the interstate to head home. As I exited the interstate, I thought I had my right toe below the brake pedal and was pushing on air. I re-positioned my foot to make sure I was on top of the pedal and re-applied the rear brakes...nothing! Fortunately, the front brakes were working fine and I continued to my house.

When I got home, I cheked the fluid in the brake reservoir and it is still full. And, there were no signs of fluid leaks anywhere on/around the bike. I'm suspecting the master cylinder may be kaput but don't know that for sure.

The "ABS" warning light is not "on" and there are no error codes showing. While parked in my garage, I "pumped the rear brake pedal" several times and got no sensation they were working, i.e., no resistance. However, as I was typing this, I went down to the garage to once again check for fluid leaks, pushed down on the rear brake pedal and got a slight resistance but have not been out to ride the bike to check the brakes again. I'm stumped.

Since I'm not a world class "wrench," this is not something I want to fool around with and will take the bike to the local shop...ugh!, probably on Sat am...first chance I'll get.

I would prefer not to go into the shop as a complete dumba$$, which, I'll admit, I'm plenty capable of, so I'm looking here for suggestions to talk over w/ the mechanic.

So, can anyone suggest what the problem might be?

 

[JamesK]

It sure sounds like you could have air in the system. Remember the Rear brake on the FJR is linked to the bottom piston on the RHS front caliper, so you could at least check to see if the front wheel stops when you apply the rear brake, but if you have air in that system than i guess it won't.

 

[Ignacio]

Remember the Rear brake on the FJR is linked to the bottom piston on the RHS front caliper....

That's true for Gen 2 bikes....not Gen 1 bikes like Brazo's 2005 would be. The back brake is not linked at all to the front.

Three things I would check off the top of my head:

• Changed fluid last? If more than a couple years....change it! If a really long time it could have killed the master cylinder.
• Brake fluid level. (You said it was OK)
• Dragging brake. Common for the rear brake to goober up and been talked about many times. Does it stay down when you depress it or does the spring bring it back to home?
• Damaged or worn out brake line. Yamaha says two years on the stock. One could be bulged or leaking.
• Master cylinder. What you describe reminds me of several cylinders in cars that went kaput.

 

[brazos parker]

Thanx for the prompt reply, Iggy.

Yes, it is a Gen I bike.

I don't think the rear brake is "goobered" up as it does spring back into position after it's depressed.

It is time to change the fluids...clutch, brake and radiator. I've got to take the plastic off to make some modifications to the bike so I've planned to change the radiator fluid while I'm there.

While the bike is in the shop, I'll just ask the mechanic to change clutch and brake fluids.

I've never changed the brake lines so that'll be a good thing to ask the mechanic.

I'm still guessing the master cylinder is toast.

I'll look in my service manual and check the front brake set-up to make sure the bike is safe to ride to the mechanic shop w/ front brakes only.

 

[Ignacio]

I'll look in my service manual and check the front brake set-up to make sure the bike is safe to ride to the mechanic shop w/ front brakes only.

You're either not going to find it in there...or it's going to blanketly just say never to ride the bike if it's not safe. There isn't something designed into it to stop working if the rear does. They are separate systems.

In your mind's eye riding from your house to your dealer...can you safely do it with just the front brake?

 

[Fred W]

+1 on the big air bubble in the rear brake line idea.

But for that to be the case, unless there was a recent (unreported) maintenance event preceding the incident, something traumatic would have had to happen to allow the air in there. I'd think that you'd have noticed some fluid leakage, or something unusual.

 

[S76]

Here is a WAG for you.

Brakes can't just go bad like that for no reason. Something happened. My guess:

1. The pedal may spring back but does it spring back all the way? If the master cylinder does not come completely all the way back two things will happen. The rear brake drags and gets hot and you will lose the pedal feel, like you described, due to the fluid boiling by the wheel and making air. Also, if the pedal does not return fully it will not uncover a little port to the reseviour so it can get some more fluid. That would cause the same thing.

I suggest checking the brake when it has cooled down for a few hours and see if it has improved. You seem to have indicated it did some. Then spray the pedal shaft with WD40 or penetrating oil or something and work the pedal by hand making sure to pull it up all the way. Keep doing this untill it is nice and free moving and returns to the very top by itself.

One other thing I have seen, but this is not likely, is sometimes the resevour (I know, I can't spell) will get a stain on the inside of the plastic and looking from the outside it will look full, but if you remove the cap and check it it may be low.

$.02

 

[brazos parker]

I'll look in my service manual and check the front brake set-up to make sure the bike is safe to ride to the mechanic shop w/ front brakes only.

You're either not going to find it in there...or it's going to blanketly just say never to ride the bike if it's not safe. There isn't something designed into it to stop working if the rear does. They are separate systems.

In your mind's eye riding from your house to your dealer...can you safely do it with just the front brake?

The dealer is only a few miles away and, yes, I feel I can ride there safely w/ just the front brakes...especially early on Sat am when there's less traffic.

I have to go thru a photo-enforced intersection on the way to the dealer. It would add insult to injury if I got a performance award for running the light when the brakes failed...LOL!

 

[brazos parker]

Here is a WAG for you.
Brakes can't just go bad like that for no reason. Something happened. My guess:

1. The pedal may spring back but does it spring back all the way? If the master cylinder does not come completely all the way back two things will happen. The rear brake drags and gets hot and you will lose the pedal feel, like you described, due to the fluid boiling by the wheel and making air. Also, if the pedal does not return fully it will not uncover a little port to the reseviour so it can get some more fluid. That would cause the same thing.

I suggest checking the brake when it has cooled down for a few hours and see if it has improved. You seem to have indicated it did some. Then spray the pedal shaft with WD40 or penetrating oil or something and work the pedal by hand making sure to pull it up all the way. Keep doing this untill it is nice and free moving and returns to the very top by itself.

One other thing I have seen, but this is not likely, is sometimes the resevour (I know, I can't spell) will get a stain on the inside of the plastic and looking from the outside it will look full, but if you remove the cap and check it it may be low.

$.02

Thanx for your comments, S76. That sounds very reasonable and, I agree, something happened between the time I left and the time I returned. I'm going to try the WD40 or penetrating oil tomorrow am. It does seem like some of the pedal resistance has returned but, I have not ridden the bike since this morning.

Also, I didn't just look in the brake reservoir window...I removed the cap and checked the fluid level.

Regardless, I don't trust my "wrenching" ability w/ something as critical as the brakes and will still have a "professional" mechanic check the brake system.

 

[WBill]

Here's an idea, just for a try, FWIW.

Put the bike up on the center stand, and spray disc brake cleaner on the rotor. Do it two or three times, somewhere that doesn't matter if it gets stained on the pavement. 'till the rotor is spanky clean. I do this about once a year. HTH, WBill

 

[Peter Murray]

Unlikely but perhaps a stuck piston in the caliper. Pull the caliper and try to move the piston.

 

[twodogs]

Linkage disconnect?

 

[Checkswrecks]

So you've got a 5 year old with these symptoms:

Pedal stroke nothing - So no pressurizing the fluid in the line, or not allowing the piston to move. If the pedal would not depress, I'd look at the slave being stuck if these were single piston systems - which they are not. Even if one of these seizes, the others should create some braking action.

Pedal won't pump up - Diminishes the bubble theory or says that you're not pumping fast & hard enough.

Pedal does come back up - Return spring

No fluid on the discs.

Known old fluid - Old fluid accumulates goo at the bottom for a couple of reasons having to do with hydroscopic absorbtion and heat. My guess is that the seal in the master leaks or that the port is goo'd open. I'd start by backflushing from the bottom end. If that doesn't fix it, try a thorough cleaning of the master, with an alcohol soak, then making sure it's dry before refilling. At 5 years, a rebuild of the calipers and new seals are a good idea anyway.

It'll be interesting to hear what your mechanic says.

 

[brazos parker]

Thanx again for all the suggestions. I think this discussion will help when I talk to the mechanic tomorrow am.

As soon as I get some info on the problem, I'll report back here.

 

[wfooshee]

Rear brake is a single piston sliding caliper.

Stuck caliper piston would not make a soft pedal. Something wrong in the master might do that. Soft pedal or completely free pedal in most likely a hydraulic problem, either lotsa air in the line, or nonfunctional master, but it's remotely possible the linkage from the pedal to the master cylinder is loose so the pedal never actually pumps the master. A mechanically loose pedal would be pretty obvious, though.

 

[brazos parker]

I got up this am and headed over to the local Yamaha dealership...you might know it would be raining! :angry: Anyway, I used the front brake only until I got to w/in a block of the dealership. I applied the back brake and it seemed the brake pedal travel was a bit "long" although it did provide "some" stopping force but less than usual...at least that was my impression.

The mechanic was not working today so I couldn't talk to him. The guy that wrote the work order said it would be Tues or Thurs before my bike would be ready...they're closed on Wednesday.

BTW, this is the first significant problem I've experienced since purchasing my '05. I'm pretty pleased at how "bulletproof" the FJR seems to be.

Stay tuned.

 

[slapnpop]

Hi Mike,

Which shop did you take it to? If it's the one on Roan on the way to Jonesboro, I haven't been impressed in the past. I hope you took it to Ken's, even though they aren't a yamaha dealer. Not open on Wednesday sounds like Jim's.

 

[brazos parker]

Hi Mike,
Which shop did you take it to? If it's the one on Roan on the way to Jonesboro, I haven't been impressed in the past. I hope you took it to Ken's, even though they aren't a yamaha dealer. Not open on Wednesday sounds like Jim's.

Unfortunately, Travis, I did take the bike to Jim's out on Market Street. The mechanic there seems pretty good...the few times I've used or talked to him. The front guy is another story. I wanted to take the bike to a Yamaha dealer even though I did think abt going to Ken's. I buy all my accessories and tires at Ken's but for this one repair, I wanted a Yamaha dealer.

I'm sure to get screwed on the cost of this repair but it is what it is...I just didn't want to take a chance w/ something like my brakes.

P.S. I did leave a copy of this thread in my tank bag and asked that the mechanic read it before he started work. I'll find out next week how this goes and will let you know.

 

[brazos parker]

I picked up my bike a little while ago from the dealer...I've got brakes!! :yahoo:

The mechanic was kind enough to walk out to the lot to explain what he found or, more correctly, what he didn't find....

1. No ABS light on and no error codes.

2. The brake pads were way beyond the wear limit...like the brake had been dragging. The part of the wear pad that was remaining was very crumbly. He replaced the pads.

3. The fluid showed signs of having been very hot. He drained and replaced the brake fluid.

4. One of the metal backings holding the wear pad showed some deformation...unknown what caused that and he had never seen that before.

5. The caliper piston showed no signs of binding.

6. The disk showed some discoloration...like it had been very hot.

7. He did a test ride of the bike after the repair and said everything appeared to be functioning normally.

Conclusion: An "unknown something" (possibly like a "small rock"...his words) was causing the brake pad to drag which resulted in overheating the fluid and that caused the loss of brakes. No idea what caused the slight deformation in the metal part of the brake pad.

The mechanic cautioned me to ride the bike normally for a week or two...but no twisties! He said to put the bike on the centerstand when I stop for lunch, etc or at the end of the ride and make sure the back wheel turns free. And, he said to visually check the pad for wear. If I see any more symptoms of brake problems, I should bring the bike back in for more checks. Finally, he said not to "ride the brakes." He has some customers that do that. I'm sure I don't but I'll now be extra cautious about what I do w/ my right foot.

OK, that's my woeful tale. Thanx again to all who provided suggestions to troubleshoot the problem.