well the other day on the way to school (in the rain), my master cylinder took a poop on me, and i had to limp to and from school like that.
how hard is is to replace one. this is a manual 4wheel drum car. auto zone has a reman one for 25.00 or somthing like that.
would all i need to do is, take off the 2 hoses on the master, and take off the 2 bolts, and disconect the linkage from the pedal? how long should it take to take the old one off and put the new one on, all bled as well?

also what would be the best way to bleed it? i heard u have to bench bleed it, is this so? and how?

thanks

aaron

What happened that causes you to believe its the master? Did the pedal go to the floor?

Chris.

If it is the m.c., I'd say its a 20 minute job for most people (2 hours for me) + an hour or so to bleed the brakes (a whole weekend if you're me, which you're not ;) )

I never bench-bleed because I've never had good luck with it. I've damaged 2 m.c.'s doing it by pushing the piston too far in. graemlins/clonk.gif

Invest in a $5.00 "one man bleeder" (which takes 2 people to operate BTW) to speed the process.

You dont have to bleed the brakes after changing the master. First bench bleed it, then install and fill with fluid. Then with the master cyl cap off tap on the brake lines coming out of the master lightly with a wrench and you will get a few air bubbles that pop up into the master. Once they stop you can put the cap on and you are done. When you remove the master there is still fluid in the lines, the only air will be at where you make your connections. Its a small amount and easy to get out by tapping the lines.

thanks guys.
i talked to my uncle about it, he says about 15 minutes to have old one off and new one on. its the bleeding that takes the longest.

i belive its the m.c. because the firewall is wet, front right where the mc bolts on to it, all the way to the bottom, and all my paint bubbled up, and is peeling off.
i didnt have time to day to check the front wheel cylinders or anything, because i had to work after school, but tomorrow it is on my agenda.

thanks again.

aaron

well thanks guys. i put on the new master cylinder and it def stops now. the only thing is i have a really low pedal. we bled the brakes, and adjusted them again. how can i get the pedal to come up? when at a light their is about an inch away from the floor.

thanks again

aaron

Aaron,
Are the rears adjusted properly?
Just a thought...

Some Old Timers claim that the adjustment of the rear shoes determine the pedal height 99% of the time.

well i know the rears lock up before the fronts. we checked the brakes and bled them as well and its still low.

how do i know when the brakes are adjusted properly?

thanks again

aaron

That the back wheels lock up before the front doesn't necessarily mean they are adjusted for maximum/optimum pedal height. Pedal height is a factor of M/C rod length and the amount (volume) of fluid that must be forced down the brake lines to expand the shoes to press against the inner drum surface.

Brake adjusting hard to explain, easier to demonstrate. (anyone else could jump in here and bail me out) The idea is to adjust the shoe expander in each wheel until each one "feels" like it has the same amount of drag when you try to spin the tire by hand. Each one also needs to sound the same as the other, (front like front, rear like the other rear). It shouldn't free-spin more than 3/4 of a turn or so when spun by hand. But, DON'T over tighten it. Most beginners worry about adjusting brakes too tight. It's not that easy to do. If you can still spin the tire by hand, the brakes aren't adjusted too tight. One spin around the block and the shoes will generally re-seat and free themselves. You may even need to re-adjust them tighter again. If a wheel free-spins with being forced around by hand, it's not adjusted tight enough. Again, it will loosen up again in the first mile driven with a couple of stop signs thrown in.

So, if nothing else changed, I.E. same/correct M/C, then you probably still need to up tighten the adjuster on each wheel a little.

Herb, thanks alot man.

so i should be adjusting the brakes with the tire/rim on, or with the tire/rim off?
i did a little searching before i posted the last post, and found that someone said you can adjust the m.c. pushrod lenght. is this correct? and how so? im going to go out and take a look at it in a little bit and see what i can come up with.

thanks again.

aaron

Not the M/C Pushrod length, but you can adjust the brake pedal height if it is not coming up far enough. Under the dash the brake pedal and rear of the push rod are connected with a pin that goes through both of them, and can be removed. Then, you can turn the end of the pushrod (it's threaded) so that it can extend (or retract). At least that's the way my 68 is setup. If you have a brake pedal height problem (and nothing else), then this will help. Make sure that it's not a brake pedal spring, or not the M/C piston is binding (although I'm not sure exactly how you would do that). It's possible that the new M/C had a different piston setup and the pushrod is going farther into the M/C bore. I have heard that there are M/C pistons with "deep" cavities versus pistons that are essentially just "dimpled" to accept the pushrod.