Polaris ATV Forum banner

1 - 13 of 13 Posts

·
Registered
Joined
·
18 Posts
Discussion Starter #1
I have a 2004 Sportsman 700. I lost all brake pressure on my last ride, and now have put new pads on and flushed the fluid. My problem is that when trying to bleed the system, I started at the rear, then right front, then left front, and all will push fluid out when squeezing the hand brake or foot brake. I never got any pressure to build up, and have now realized that fluid is pumping between the 2 reservoirs. If I pump the hand brake, the auxiliary reservoir fills up and leaks from the cap, and vice versa with pumping the foot brake, the handlebar master cylinder fills up to the point it will leak out of the cap. The pressure never builds, the hand brake WILL apply pressure to the pads, but it goes to the handlebar with little resistance.

Here is my question: I'm fairly certain I have a bad master cylinder, but which one? Or could it be both? Its comical how much fluid I have gone through. I do have a mighty vac, and when I pump it, pressure holds, and fluid does come through. I dont know if I'm missing something, or what is going on, but I have been bleeding these brakes off and on ALL DAY. Any help is greatly appreciated, I am fairly mechanically inclined, so if I need to take the MC apart, I'm comfortable with that. I just want to try to avoid buying 2 new master cylinders if I only need one. Or maybe I dont need any, I'm just not bleeding correctly. I'm at a loss! Thank you
 

·
Premium Member
Joined
·
8,198 Posts
I'm inclined to say that the rear caliper is bad. That's the only point where the two systems are connected. Other then that it would seem both mater's are bad and not preventing back flow via a check valve.
 

·
Moderator
Joined
·
9,860 Posts
Rear caliper needs rebuilt. It has a stepped/two-sided piston. One for the hand brake side and one for the foot brake side. They are SUPPOSED to remain separate and work independently. If the seals leak allowing the fluid to bypass from one side to the other rather than push the piston you get the issue you describe.
Bottom line...rebuild or replace the rear caliper.
 

·
Registered
Joined
·
18 Posts
Discussion Starter #6
I hope you guys will still reply to this thread. I replaced the rear caliper and nothing changed. Still zero pressure at either brake, both grab but they still bottom out after a lot of bleeding. And just like before, when I pump the hand brake, fluid fills up the lower reservoir, and when I pump the foot brake, fluid fills the handlebar reservoir! I did also notice that when I pump the foot brake, the fluid level drops with each pump, and actually rises a tad when I let off. I'm at a loss. The only thing I can come up with is that both master cylinders have gone bad. I know stranger things have happened, but why would all my brakes grab the rotor, but never build pressure at the lever?? I could use some advice as to what to go after next. I'm just spraying parts at it now.
 

·
Premium Member
Joined
·
8,198 Posts
Ok so this is very odd but all I can say is try the handbrake master first. They are known to have issues and be finicky.
 

·
Moderator
Joined
·
9,860 Posts
LOL, yeah we'll respond to you to try to help you get it fixed.
Did you replace the rear caliper with a NEW or a used one?
Are you getting any pressure out the bleeders?
If you get real pressure out the bleeder then the MC is not bad.
Are you keeping the reservoirs completely full while trying to bleed?
If they get low during the process you have to start all over again since air has been drawn into the lines.
So far as I know, the ONLY way fluid can transfer from one side of the system to the other is to bypass the caliper piston seals.
If you have air in the system it can't escape until you push or pull it out. Air will compress but fluid won't so if there's air in the lines you'll have no firm pedal or lever till you get it out.
If you KNOW the caliper is good, take BOTH covers of the MC's and fill them to the top. Then crack BOTH bleeders open on the rear and keep adding fluid into both reservoirs to keep them completely full at all times until you see fluid leaking out both bleeders steadily. May take a few minutes to drain down. Don't worry about moving the pedal or lever while doing this. Once you see fluid coming out both bleeders close them, top up again and start pump, pump, pump, pumping (10 or 12 or 15 strokes) on the foot pedal repeatedly and hold down while briefly cracking the foot brake bleeder ONLY. Keep the foot MC reservoir full at all times. Repeat as many times as it takes to get a firm pedal. If it won't pump up the MC is bad. If it goes to the other side of the system the caliper is bypassing...so you know what has to be replaced.
Then move to the hand brake and start with the rear caliper again but the on the OTHER bleeder going through the same process. Then move to the front right caliper...same thing. Then move to the left front caliper...same thing. Always keeping the reservoir completely full till you are done. You can adjust the fluid to the correct level AFTER you're done.
If that don't work I don't know what to tell you. :nixweiss:
I've rebuilt, replaced, torn apart and put back together dozens of brake systems and never had any trouble like you describe.
 

·
Registered
Joined
·
1 Posts
This is crazy, because I'm having the same issue. I replaced the rear caliper twice with new. Replaced the handbrake M/C and the footbrake M/C also both new, Vacuum bled and gravity bled all calipers and still cannot get any pressure on the handbrake. Went through 2 quarts of fluid. checked for leaks along the whole system and still no luck. This problem really defies logic!
 

·
Registered
Joined
·
1 Posts
Maybe one of the rubber brake lines is bad like I have seen on cars . I have seen the rubber on the inside has gone bad and preventing proper flow of the brake fluid in either direction or slowing the flow of fluid down or some of the nylon cords have broke in the rubber brake line allowing the hose to expand when brakes are applied or if the brake lines have braided steel on the outside of the lines check for a worn out spot on the steel braided lines from rubbing on some thing if the braided steel has a worn through spot the line could expand at that spot and give bad brake performance. I could be way off base but I hope this helps it sounds like you have tryed evreything else .
 

·
Registered
Joined
·
5 Posts
I hope you guys will still reply to this thread. I replaced the rear caliper and nothing changed. Still zero pressure at either brake, both grab but they still bottom out after a lot of bleeding. And just like before, when I pump the hand brake, fluid fills up the lower reservoir, and when I pump the foot brake, fluid fills the handlebar reservoir! I did also notice that when I pump the foot brake, the fluid level drops with each pump, and actually rises a tad when I let off. I'm at a loss. The only thing I can come up with is that both master cylinders have gone bad. I know stranger things have happened, but why would all my brakes grab the rotor, but never build pressure at the lever?? I could use some advice as to what to go after next. I'm just spraying parts at it now.
Did you ever get this resolved? I'm having the same issue. Driving me nuts!!
 
1 - 13 of 13 Posts
Top