Help!! Rear brakes won't bleed
 

I need your help. I know there are numerous threads on this but I haven't found anything that will help solve my issue. 2001 Yamaha Kodiak 400 4x4. Just rebuilt the rear caliper and installed new pads. The problem is that it doesn't matter how much I bleed them, I only have very little brakes. I have a clear tube on my bleeder into a jar of fluid. I am pumping the lever (have tried it slow and fast, it never gets hard), holding it in, cracking the bleeder, tightening the bleeder, releasing the lever. I have done this for about 6 hours total and have went through 2 bottles of fluid. What am I missing? Please help.

Looks like the same basic rear master cylinder that we had problems with on Ktms.Seals would suck air,wouldn't build up pressure. You can try a Mityvac,may or may not help on these small master cylinders.Plus do you have the caliper pistons pushed in too far?I've had that happen on some calipers as fluid may not have enough room behind the piston to build up.If it comes down to the master cylinder, rebuild kits cost close to what a new master cylinder does,at least at this site.Dirt Cheap Yamaha, Honda, Arctic Cat & Polaris OEM Parts & Accessories – Cycle Parts Warehouse Others may be able to help you better that have gone through this.

hmmm. I may try to push the piston out some. There's not much room with the new pads though. Thanks for the ideas. I guess if that doesn't work, maybe the master is to blame. I mean, it should build up pressure until the lever gets hard.

Had that happen on my Tri-Z front brakes. They would not bleed with the master cylinder. Everything was basically new. Had to bleed them with the automatic bleeder and they worked fine after that.

This is not regarded as good practice but it works. Clamp a pair of vice grips on the rubber pipe leading from the master cylinder so that they stop the flow of fluid. Open the bleed nipple, remove the clamp, press the lever down fully and refit the clamp, let the lever return then remove the clamp, do this several times, then tighten the bleed screw and try the brakes. Don't forget, the first couple of pumps may just be moving the brake piston(s) out.

I will try that. I don't care if it's frowned upon or not. Ha! As long as it works. Thanks, man.

Well I can't bring myself to crush the brake line coming off the master cylinder to try that. I hate being defeated.

Is your problem that the brake never gets real hard? Or something else? You didn't mention if you checked for leaks(brake leaks can be very very small, use clean paper towels to wick for fluid). On to your problem if it is getting hard but not giving you good stopping power I would re-disassemble the rear caliper and make sure it does not have any issues(binding piston etc.). If you can't get a hard pedal I would do whats called a bench bleed on just the master cylinder(MS). You will have to remove the master cylinder assembly and hose from the caliper and then you take that over to the bench and you bleed the MS back into itself or you can do it into a separate container of fluid. Just don't let the reservoir go empty and pump very slowly and do not go all the way till it bottoms out or you could damage the seals. I suspect that when you disassembled the caliper air may have got back to the MS and sometimes trying to bleed the "normal" way won't get it out. You will want to use a pair of hemostats to clamp down on the rubber hose near the caliper fitting so that you don't drain the hose after bleeding the MS keep the fitting submerged and put the hemostats on. Only remove the hemostats once you have reinstalled the banjo bolt into the caliper. Then put the assembly back on the machine and bleed the caliper as normal. Hope this helps.

I have done many things on many different types of vehicles but have never had to bench bleed a master. Have heard of it and it makes sense. I guess the reason I didn't think of this is because I have never done it. I will definitely try this because it may just give me back my sanity. Thanks a million, brother.

No problem just let us know where you end up. We may have a few tricks up our sleeves to get you going.