View Full Version : Master Cylinder Leak

07-28-2007, 11:07 AM
I recently purchased a 1973 Javalin w/ 360 4bbl. All smog stuff has been removed. My master cylinder leaks fluid out from underneath the cover. Any ideas what is causing this? The car has front disc brakes. any help would be appreciated. I put a new pice of vacuum hose from the brake booster to the intake which is an edelbrock performer. from the looks of the outside of the master cylinder and the inner fender its been leaking for some time.

07-28-2007, 12:50 PM
How does the rubber gasket look inside the cover?? Could need replaced.

07-28-2007, 03:11 PM
It doesn't seem to be dried out.

07-28-2007, 04:42 PM
I would take the cover to the parts store and get a new one. Also see if the bar coming across has enough pressure to hold it down.This way it would be process of elimination to be sure.And then you can go from there.
It's not a chrome cover is it???? Might not be a good fit from an after market product.
Let us know what happens.

07-28-2007, 07:28 PM
It's not chrome. I'll try a new gasket and new hold down rod if I can find one.
Thanks for the help. I'll let you know how it works out.

07-28-2007, 11:26 PM
just a thought here,try bleeding the brakes,start at RR,LR,RF,LF. you should get GOOD flow at all wheel cylinders/calipers.you will need a helper to do this.open bleeder valve,have helper push pedal to floor and HOLD it down.close bleeder screw THEN have helper let up on pedal.this is IMPORTANT-DO NOT LET THE PEDAL COME BACK UP WITH THE BLEEDER SCREW OPEN!!!!!if you do not have good flow at the rear brakes(as i'm suspecting)the your metering valve is only allowing the front brakes to work.i've seen this before,the master cylinder will bypass all the fluid back into itself.if you are not experienced in doing this find someone who is.a brake shop will bleed and adjust you brakes for a reasonable charge.also only fill the master cylinder to 1/4" from the top.unless that rubber seal is no good,you may be looking at another problem

07-29-2007, 10:07 AM
Will pulling it thu with a suction pump do the same thing? It only seems to be the front resivoir that is down on fluid when I check it.

07-29-2007, 12:36 PM
yes but no,the suction method works great for removing air but you are looking for volume of fluid going to each wheel,that is why i suggested that.also is the master cylinder blowing it out through the cover or is it leaking where it bolts to the booster?i forgot to ask-how does the brake pedal feel?when the motor is running does it go almost to the floor?also if you hold your foot on the brake,will it slowly drop after a minute or two?

07-29-2007, 02:45 PM
At first the pedal would go towards the floor when the car was at an idle. I changed the vacuum hose and it seemed to get better. The fluid leak is coming from under the master cylinder cover. I can see the marks where it's running down the side of the master cylinder from under the cover. Going down the road the car seems to stop fine.

07-29-2007, 04:47 PM
sounds like you might want to bleed the master cyl also,do this before the wheels.loosen each fitting (at master cyl)with a line wrench 1/4 turn,have helper push pedal to floor,tighten lines BEFORE helper lets up on pedal-do this several times making sure not to let the fluid level get too low,then do each wheel in sequence i last posted-again keep an eye on the fluid level as you do this.tell your helper not to push on the pedal real hard-just a steady even pressure untill it hits the floor.and remind them NOT to let up untill you say so,AFTER closing the fittings(master cyl)/bleeder screw(wheel cyls&calipers).do the wheels ONE wheel at a time,you should see a steady stream of brake fluid coming out each time with no air pockets(foamy fluid).

08-19-2007, 05:46 PM
It looks like it was the cover and gasket. I replaced both and scraped off some of the crystalized fluid where it had leaked, and it looks like it stopped leaking. Thanks for the help.

08-25-2007, 08:36 AM
glad to hear it was a simple fix,but now you have an idea on how to bleed your braking system.i go a little overboard because i like to see someone check everything on their cars because sometimes you need to start at the beginning in order to solve the puzzle-especially when others have "worked" on the car.AMC-ya