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kd4tsc
23rd April 2007, 19:13
I decided to change the front and rear brake pads on my '98 883. I took the brake assemblys off both the front and rear, removed the old pads, and installed new ones. No problems. In order to fit the assemblys back on to the rotors with the new pads (which are thicker due to being new) I had to depress the piston inside the brake assembly cylinders. I did this by opening the bleeder valve and compressing the piston. Of cours brake fluid shot out, but the pistons were all the way seated and now the brake assmblys fit onto the rotors. I re-installed them, and then began the bleeding process (due to the brake fluid which came out when I compressed the pistons). I got the rear brake done without any problems. Bled, tightned bleeder valve and now I have rear brake. Perfect! Now to the front: I attempted the same thing as far as bleeding the front system after re-installing the assemblys on to the rotors. Problem is; the front brake lever doesn't seem to pump fluid into the brake. I, of course opened the bleeder valve, depressed the lever, held it down, and closed the valve. Doing this several times works the fluid down in to the brake. Nothing was comming out of the bleeder valve. I then decide to disconnect the brake line comming down from the brake kever and tried pumping from there. I went through the standard bleeding process and of course, depressing the brake lever should've pumped fluid down to the banjo fitting, but nothing is comming out. I had the top of the resevoir off and I didnt see any bubbles or anything while depressing the lever. Could I have a problem in the master cylinder, and if so why? They were working fine before I changed pads.
Please help. I gotta ride.
Thanks

jbird526
23rd April 2007, 19:25
Brakes can do some funny things sometimes. I just removed the rear brake master and caliper from my 82 to flush out and rebuild. To reprime I did the old pump and tap which is basically just leave the bleeder screw open and put your finger over the opening while quickly pumping the brake lever. To do this you just need good timing between hands. I then went to the front calipers and did them and it took considerably longer which doesnt make sense considering gravity should do most of the work. The best way is to buy a brake bleeder at Sears or some autoparts place. they work well and quickly. You can also run a hose from the bleeder to a bottle of brake fluid. As you pump the lever you are bleeding the air out or the line without sucking any air back in. This is usually what I do but recently didnt have any hose to do it.

kd4tsc
23rd April 2007, 19:44
I did use a brake bleeder (vacuum pump), but it's not sucking anything down into the brake from the resevoir. This is why I think I may have a problem in the master cylinder. Problem is, why? since everything worked perfctly before I started messing with it. I thought I'd try to solicit some ideas before I bougfht a Master Cylinder re-build kit and tore in to that.

jbird526
23rd April 2007, 20:18
First make sure you have been putting the right fluid in, the DOT rating. Ive seen master cylinders eaten up by the wrong type and still partially work until lines are disassembled. Before you rebuild take the lines off and spray brake cleaner through them to make sure there is nothing in them. Then spray out the calipers. This is best done by taking them off so the brake cleaner can dry out. Definitely spray out the master cylinder. Since you are having problems you might as well take the time to make sure everything is clean and free of blockage. Just think of it as maintenance instead of a repair and you wont be as frustrated. The master cylinder plunger might be distorted, torn, or a small piece has come off and blocking the flow. It is doubtful but there is a blockage but if you dont check that always ends up being the problem in the end. At least if you have my luck.

jbird526
23rd April 2007, 20:22
Also try taking off the line at the master cylinder and use the vacuum pump to pull fluid just through the line. Ive had bad vacuum pumps before and thought it was the master cylinder. If the vacuum pump doesn't pull through disconnected lines then something is wrong with the pump. PS make sure there is fluid in the lines.

jbird526
23rd April 2007, 20:33
a buddy of mine had something similar happen to him on his 85 softtail. He got a rebuild kit and fixed the problem. The old one didnt look bad so we couldnt figure out exactly what the problem was. I would drain all the fluid and use brake cleaner to make sure there isnt any buildup in the master cylinder. Ive seen some nasty buildup and corrosion from age and people using the wrong DOT fluid.

kd4tsc
23rd April 2007, 21:02
OK, I think what I'll do is disconnect the banjo fitting at the master cylinder, pump it, and if nothing comes out, that would indicate a problem with the master cylinder. In that case, I'll dis-assemble, clean the master cylinder parts, re-assmble, and try again. If I still get no fluid comming from the master cylinder after cleaning, I'll do the re-build kit. Does this sound like a plan? I'll let ya know what happens.

jbird526
23rd April 2007, 21:07
Yea, I was tying to give you every scenario that I have come across. I've had some strange brake problems in the past. Hope everything works out quickly.