Here is my latest problem....

I put new pads in all calipers, and I had to rebuild the rear caliper, new seals and I took a scotch pad to clean the crud off the pistons, re-assembled everything....

Now, in bleeding the brakes, when I apply pressure on the front lever to bleed the fronts, the fluid and pressure build up, in the REAR brakes reservoir.

Yes, the front fluid is going into the rear brakes reservoir, not allowing me to build up enough pressure to even use the front brakes, let alone enough pressure to bleed them correctly.

I know that the front lever is tied into all 3 brakes, but i am pretty sure that when trying to bleed the fronts, it is build up in the rear's reservoir, that this isnt right.

Also, when I press all the way down on the rear brake pedal, this closes the rear brake, and yes, I am then able to use the front brake, and bleed them with a good amount of pressure, but as soon as i let off of the rear pedal, the pressure goes away...

So, I am led to believe that either I need a new rear master cylinder, or a rebuild kit.

has anyone else experienced this issue?

Thanks

Justin

 

You need to bleed the lines from the longest to the shortest.

And then take the caliper off the rear. and hold the piston back with a c-clamp. this will force all line pressure to the front alone.

Move the C-clamp around as needed to bleed them all.

 

If pressure is building up excessively in rear resevoir then probable o-rings seeping in rear caliper(o-rings between the rear caliper halves) Try bleeding as suggested above,BUT if doesnt help,could be the problem.

 

Hmmmm...

I rebuilt the rear, and I put a new little o-ring in, maybe it shifted during re-assembly, this will be my first check...

As for ezdarr's suggestion, I don't see the benefit of using a c-clamp to hold the pistons back. Why not keep the caliper installed, and the disk between the pads will hold the pistons in place also, using a c-clamp just holds them further back in the cylinder.

still very intriguing that the brakes work fine and bleed fine just as long as the rear brake lever is pushed all the way down.

This is why I thought that the pressure is getting through the rear master when the brake is relieved, but no pressure gets by as long as I keep the rear lever zip tied all the way down...

 

The reason for holding the piston back is to not aalow any fluid to travel down that particular line.
When its bolted on and working the pads. the piston will move in and out a slight amount. This can be VERY frustrating when bleeding ATV brakes.
As it will NOT allow the trapped air bubble to move further down the line. It will simply move back and forth.

Guys, I repair ATV's and cycles as a hobby and for extra cash. So I get to bleed brakes more then I care for.
There are some models. That I literally have to remove the caliper (while hose is attached) manuver it Up above the master cylinder, while bleeding it, to get the air out of the line. Its a big pain in the ****, but it works and work really well..

If you want to fight piston movement, go for it. If you want to spend 3 hours getting nowhere bleeding brakes go for it, If you want to waste alot of fluid while making a mess, Go for it!. But not me, no way.
I Do anything I can to get that darn bubble out of that line as fast as possible!

Yess I know about the mighty vac and the reverse bleeder systems. But those break and are unreliable.
Use the sytem as it was intended , just BE SMARTER THAN THE PART!
Dont let a bubble get the best of you. Figure out where its getting stuck and Do what you have to to get that fugger moving!

 

I will defintely give you're technique a try....

I have just never seen any brake system ack like this.

I have a 2007 sportsman also, and it has the same basic setup, but I can bleed the brakes fine with all the calipers in place...

This scrambler situation is just funny.

One thing to add. When I pump the front lever, the fluid fills up the rear reservoir. When I pump the rear brake, the fluid fills up the front reservoir.

The fluid is pressurizing the brakes, just moving back and forth between the reservoirs.

 

definatly in the rear caliper then. those are made with two different systems in one small space. either the caliper has too much wear or something got installed wrong on reassembly