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hello chris:
i am experiencing problems with my front brakes, i have a 1982 yahama maxim/xj550 that has a problem with the master cylinder. the piston inside dosent seem to be pushing any fluid out. i have checked the levels and they are ok. i have a clymer manual that describes different operations, but dosent get too specific about the master cylinder.i have dissasembled the piston and checked the components, and they all seem to be fine. i do notice that there are two holes on the bottom to let fluid into where the piston is, one is about 3mm and the other is very small like a pinhead size. when the piston is at rest all the way out looking in the master cylinder i see that the end of the piston dosent come back far enough to let the fluid into the chamber, and get pushed into the system creating pressure. thank you ,kevin
Answer -
Hi Kevin.
If you look at the last descriptive sentence that you sent, you will see that you've answered your own question. The piston is not retracting completely.
Get yourself a master cylinder rebuild kit and rebuild the master cylinder. Make sure that you clean it out properly before installing the replacement parts.
Good luck.
FALCON
hello:
thank you for answering my question, when you say that the piston isnt retracting all the way, what do i do if there isn't any more room for the piston to move. there is a spring clip that holds the piston in place so it cant move any further.i am afraid that a new rebuild kit might give me the same results. is there any other piston kit to use?(shorter)maybe?
thank you:
KEVIN
Answer -
Hi Kevin.
I must appologize for my response. After sending that off to you, I had to take a second look at master cylinders, since it had been a while since I had worked on any, and you are correct. It doesn't go back any further than you had noticed.
I was wondering if you have bled the brakes. Air in the line will have the same effect and if you have any high spots, that are higher than the master cylinder piston assembly, then air will get trapped there instead of working it's way into the master cylinder. If this is the case, there is a process to eliminate that reverse trap problem during bleeding proceedures. It also works for Hydraulic clutches as well.
here it is:
1) Bleed the clutch/brake line like normal.
2) Put a wrench on the banjo fitting and squeeze the lever.
3) (NOTE: Use a box end wrench for this) While holding the clutch/brake lever in, crack loose the fitting and reclose it quickly. Have a rag over the fitting connection that you are working on because it will spit at you as pressure expells the air and a little fluid.
IMPORTANT NOTE: Do not release pressure on the lever till the fitting is tightened back up or you will suck air back into the line.
4) Test the clutch/brake again. If done correctly, you will have pressure near the beginning of the lever movement rather than at the end.
5) repeat as needed, but should not need more than 2-3 times.
Good luck.
FALCON
hello:
thank you again for responding, i have tried to bleed the brakes several times but there dosnt seem to be any pressure coming from the master cylinder. it seem like because the piston dosent come all the way back the fluid dosent get into the chamber to get pushed out to create the pressure to force the air out of the line.the master cylinder is the tallest of the system so there arent any high spots.
AnswerHi Kevin.
Is the banjo fitting (the nut on the end of the master cylinder that holds the line on) higher than the piston? If so, then it is a high spot where air will hide.
If not, then you are fine with that and the only thing that it can be is that the master cylinder needs a rebuild kit. The rubber parts in there do not last forever and if all else is correct, then that has to be the problem (assuming that there is no blockage in the line anywhere between the M/C and the caliper).
Good luck.
FALCON
