I have a 1997 Polaris Sportsman 500 and I cannot get the brakes to bleed. It has a new master cylinder along with new pads and rotors up front and just new pads out back (rotor was in good shape).

I can get the fronts to bleed no problem but I cannot get the rear caliper to bleed. The master cylinder has been bled as well. I'm also using a Mity-Vac.

I rebuilt the rear caliper thinking that there was an issue but that didn't help. When I pulled the caliper off I tried pumping the handle thinking there might be a clog and fluid was not reaching the caliper. I did and fluid came out the line. Once the caliper was rebuilt I also pulled the bleeder screw out of the caliper to see if fluid was in the caliper and it is. It even pumped out when I pulled the brake leveler. The crazy part is that I cannot get any fluid to come through the bleeder valve by either using the Mity-Vac or the pump, hold, crack bleeder method.

There is absolutely no resistance at the brake lever either. I'm at a loss on what to do next. Thoughts?

If I squeeze the brake level I can see the caliper pistons move slightly so I know they are not stuck. There just isn't enough pressure to fully operate the calipers

 

Rear brake is mechanical and hydraulic. You have to turn the outer adjuster screw to where the petal lifts up from the floor board about 1/2" from the bottom of the lever. Problem is that many snap from corrosion over the years. You can take a chance on it. If you get it adjusted,then you can resume bleeding. Item #34.
If I remember correctly,this screw is reverse threads.Turn left to tighten,right to loosen. If that doesn't help you may have a frozen piston or seal are bad. Shows the piston and seal kit if you haven't already replace them.

 

The lever and pedal are in the same position as they were before I took them off.

I also replaced all the seals in the caliper when I rebuilt it. I also made sure to wipe down the piston to make sure there was nothing stuck on it.

I have fluid in the rear caliper and it pumps out when I press the lever only if I remove the bleeder screw. The interesting part is that I cannot get any fluid to go through the bleeder even with the Mity-Vac.

I keep going back to thinking that something is wrong with the master cylinder but it is supposedly a brand new Polaris MC. I bled it how the service manual says as well.

 

Is the bleeder open? How I bled them was use the mity vac under pressure and press on the foot brake with my hand in rapid strokes.Plus one thing that people have done is to have the piston pressed back too far to where fluid can't get fully behind it to force it out against the pads also. Too many parts in this caliper that have to be right.Only used two year(96-97) Changed for the 98 models up.

 

I'll try to pull the piston out a little and give it more clearance. With how it is now the rotor barely fits between the pads but it might need that little extra clearance inside the caliper.

Yes, the bleeder is open. With the bleeder closed I can get pressure to hold with the Mity-Vac and as soon as I crack open the bleeder I can hear air coming through the bleeder and tube of the Mity-Vac.

I'll give your method a shot and see if that works.

 

Still sounds like possible air in the system also. These older systems didn't have a separate rear master cylinder either and had a long way for fluid to travel. I'd crack the bleeder,have the mityvac pumped up,use the hand brake also and keep an eye on the master cylinder reservoir level. Some of these old ones just take time to fully bleed.

 

Thanks. I'll try and rebleed everything this weekend. I have new bleeder valves for all calipers as well just to make sure they are not clogged.

I soaked the rear one in brake cleaner and blew it out with compressed air and it is clear but figured it can't hurt with how cheap they are.

 

Still was not able to get the rear caliper bled.

I pulled the banjo bolt from the master cylinder and put my thumb over the opening to bleed it. I could feel pressure building behind my thumb and could release air by slowly releasing my thumb but my handle never got more firm. It was still very soft and pull very easily to the handle.

Could the master cylinder be bad and the plunger not working properly?

 

Possible if it's the original. You can remove the line from the mater cylinder and block off the opening with your thumb.Don't get any fluid on the plastic.You can tell for sure if it builds pressure or not. If it's weak,kits are 55 bucks.1997 Polaris SPORTSMAN 500 (W97CH50A) Controls Master Cylinder/Brake Line Sportsman 500 | Cycle Parts Warehouse
Chinese replacement are cheaper than the kits. Don't know how good they are.LEFT FRONT BRAKE MASTER CYLINDER FOR POLARIS SPORTSMAN 400 500 550 600 700 800 | eBay

 

It is not the original. It is a brand new Polaris OE master cylinder that was put on there before I bought it. It builds pressure if I put my thumb over it but there is still no resistance to the level at all.

a buddy at work said he had the same problem with his bike a while back and it ended up being a cracked caliper. Could there be a crack or anything anywhere that is causing it to no bleed but not leak?

There is no leaking come from any lines or anywhere around the calipers.