Can't get the rear brakes to work???

[JEEP FARM]

Hey guys,

Well at the end of last season my brakes stopped working. Sure enough the pads were toast. So I replaced them and bled the brakes with new brake fluid.

I am getting some movement from the caliper piston, but not enough to stop the tire from spinning by hand?

Hope you guys can help, it's getting really warm here!

 

[Blackcat]

Did you pump them up before you tried stoping the tire? Did you get a good amount of fluid when you bled them?

 

[uts]

Is the lever feeling spongey? If so you may need to bleed again as ther is air in the line.
If the lever feels hard and tight you may have a seized caliper piston.

 

[rmc_olderthandirt]

My first guess would be that you didn't bleed the brakes properly and you actually "unbled" them, meaning that you let air get into the lines.

It is a topic that has been covered many times, a quick search of the forums turns up a lot of hits. Here is a good one:

http://www.dirtrider.net/forums3/showthread.php?t=104165&referrerid=68872

 

[JEEP FARM]

Hey guys!

Well I have tried everything now and still can't get the rear brakes to firm up!

So my next question is! How can you tell if the master cylinder is shot or not?

The pedal just feels like it's doing nothing. It's not plunging anything. The only thing giving it resistance is the spring attached to it!

Thanks, Jay

 

[rmc_olderthandirt]

Will it pump brake fluid through when you bleed the brakes?

It is possible for the master cylinder to have totally failed but it is rare. Much more common is to have it leak, either externally (which makes a mess and loses brake fluid) or internally, which results in the pedal slowly moving under pressure until it runs out of travel.

I just have the feeling that you didn't bleed the brakes properly. Tell us how you did it.....

Rod

 

[CaptainObvious]

The rear brakes can be hard to bleed because the reservoir and master cylinder are almost inline with the caliper. Remove the reservoir and master from the subframe and raise them to seat level. Then bleed the system.

 

[rmc_olderthandirt]

The rear brakes can be hard to bleed because the reservoir and master cylinder are almost inline with the caliper.

It shouldn't matter.
step 0: Attach a hose to the bleeder nipple, route the free end into a jar.
Step 1: check the fluid level
Step 2: apply the brake, hold it depressed
Step 3: Open the bleeder nipple.
step 4: close the bleeder nipple.

Repeat steps 1-4 as necessary.

If you fail to do step one, or release the brake pedal before closing the bleeder nipple, you start over.

Rod

 

[JEEP FARM]

I know how to bleed brakes with no problem. I may have let air into the system though, while trying to empty the system of old brake fluid in exchange of new fluid.

I opened the bleeder valve and pumped the old fluid out by pressing the rear brake pedal. At this point I was not really worried about air. I just knew that in my manual, it said not to mix different and old and new fluid. I figured I could always get the air out later by just bleeding them. I didn't quite workout that way as you all can tell!!

So let me have it, lol! I am going to try and back bleed them again!

l8ter, Jay

 

[JEEP FARM]

Ok so I just spent the last two hours back bleeding the brakes. There is no more bubbles or cloudness to the fluid when pumping up the system. I have nothing but a sloppy brake pedal.

There is no fluid leaking anywhere. I am thinking there is something wrong with the master cyl. It doesn't seem to be pumping anything. Maybe the piston seals? I don't hear any fluid swushing by the seals though!!

I'm stumped! :bang:

 

[Chili]

Have you tried cleaning the pistons and all the areas around the piston? Sometimes they can get pretty packed with built up crap and need to be cleaned out. Also did you change the pins with the pads? make sure the pads aren't hanging up on the pins.

 

[BSWIFT]

Have you tried cleaning the pistons and all the areas around the piston? Sometimes they can get pretty packed with built up crap and need to be cleaned out. Also did you change the pins with the pads? make sure the pads aren't hanging up on the pins.

I'll vote for that!

 

[rmc_olderthandirt]

I opened the bleeder valve and pumped the old fluid out by pressing the rear brake pedal.

No, that doesn't always work.

Follow the steps I outlined, exactly. Press the pedal, open the bleeder, watch the fluid spurt out, close the bleeder, release the pedal. Repeat a bunch of times.

Rod

 

[mbaird]

if the fluid is spurting out with pressure I would assume your master cylinder is OK.
If the bike has sat for a while then it may be the caliper.

Remove it from its mount ,leaving it connected to the hose and see if the piston moves at all when you push the brake
lever. DONT GIVE IT A BIG GOOSE ! you may pop the piston
out of the caliper.

just a thought

 

[JEEP FARM]

Chili,

Are you talking about the piston in the the calipar or in the master cyl? I never changed the pins with the pads. I just used whatever had with the new pads. I guess the pins do not come with the pads eh! Maybe this is what it is! They only thing is though. I think that there should be alot more pressure in the lines then there is. When I crack the bleeder valve. It's just kind of dribbles out of the end!

Thanks, Jay

 

[JEEP FARM]

Bump!

 

[Blackcat]

Correct me if I'm wrong but don't they sell rebuild kits for master cylinders. I know master cylinders cost about 100 bucks. But if you can get a rebuilt kit it should be a lot less. That's what I would do. Cause you should be getting more fluid then you are. Also when you redid your breaks was there any chance that you pumped the breaks while the caliber was off the bike? Cause that would pop the piston and you would have to rebuild the caliber if you did that.

 

[macko00xj]

as a mechanic i ran into this problem one time, the problem is that air will sit in the highest place and brake fluid will sometimes not pump it out. make sure that the line is straight and does not go up and down like a sidways "S". hearing what you have said air is not your problem. here is one major problem with disc brakes. when you use all of your brake pades and grind into the rotor, the heat generated by friction heats the brake fluid to much since it can not disipate the heat properly. i would order a caliper rebuilt kit, and a master cylinder kit. clean the caliper/master in warm soapy water(dish soap) and blow them dry with air. rebuild and rebleed, that should take care of your problem. it also would not hurt to buy a new line. hope that helps.

 

[jason33]

yea fluid should fly out of there with pressure on it-i would say buy a rebuild kit-
theres like 3 o-rings in it- clean it clean the piston ,and re assemble it

 

[WaldoVH]

Even if the master cylinder is blown if you crack the bleeder valve and push the pedal down you should be getting a healthy squirt of fluid at the caliper bleeder valve if there is no air in your line. It sounds like it is just dripping out and not pumping out. If you popped your rear caliper you should still be able to get a big squirt.

All that fluid you dumped in where did it go? Did you get it to pump through with healthy squirts? If your master cylinder is blown you will probably see fluid leaking out of the front of it.

 

[76GMC1500]

My friend's GSXR had a blow master cylinder. It would hardly pump at all. Everything inside apeared fine and there were no external leaks, but I rebuilt it and now the brake works great.

 

[woodsrider200]

No rear brakes

While the caliper is installed,put a C clamp on the caliper to squeeze it while you try to pump it up. By compressing the piston while pumping the pedal it should firm up.Good luck.