New Master Cyl. Did I Brake it?

Hey fellas, so I tried another MC in my quest for pedal pressure. It's a dual circuit unit on a '63 Dodge 1/2 ton, I got the part # from the Sweptline forum so I figure they should know. I went to bench bleed it and I don't know if pushed the piston in too far and damaged it but here's what it's doing...

when the piston is slightly depressed the chamber for the rear brakes instantly pushes fluid and has a healthy squirt out the top the resivior

the chamber for the front brakes doesn't push much or with much force until you get way down in the bore possibly bottoming it out. It definately goes in more than an inch before you see any activity. I also get bubbles from the holes in the bottom of the chamber but it doesn't seem to take any fluid or push anymore air out.

Is that normal on these types of MC's? I'm hoping I didn't damage this thing on the first initial strokes by pushing it too far.

Thanks Guys.

 

...sounds like front reservoir is not pumping as it should; I 've had a few new ones do that....

 

First, you will not damage a master by full stroking the piston(s). That's the only way you will get a good bleed.
Second, it's always best to diss***emble the master and check for damage and/or debris, especially a reman.
Do you know the original application of the master?

 

Do you have the lines hooked up correctly? Normally the "rear" chamber (the one closest to the firewall) is for the front brakes. Many modern master cylinders work in two stages, which will apply the front brakes first until pressure builds up, then apply the rear brakes. This helps keep the rear brakes from locking and spinning the vehicle out. It really depends on what master you are using.

 

Did you bench bleed the master? some people say its not necessary but i always do it still.

Also its common for it to squirt up when you depress the pedal, i alway keep the cap on when im pumping the pedal, cause if you dont it will make a mess real fast.

And i never let the pedal go all the way the floor, it is bad for the master to be bottomed out, i usually put a 1/2 or 3/4 thick board to keep it from going all the way down, it may take a minute longer to bleed but ive never had any problems with remanufactured mastery cylinders like alot of people have.

JEFF

 

Yes, they are hooked up correctly. See that's what's tripping me out on this thing, the pot closest to the firewall (front brakes) does nothing until you really push the piston waaayyy in there, while the pot for the rears pumps instantly... which would mean the front brakes would not be applied first. This is the second one I've observed acting like that while bench bleeding. I took the first one back, but I don't know... two bad ones in a row?

Thanks again guys

 

Depends where it was purchased at you can have a dozen bad ones! having worked for a reman distributer back in the 80's we had a string of bad power brake cans come back and found out the rebuild guts were bad. after 2 bad ones get your money back and and find a brand new one. what is the duel master app for?

 

It still has air in the system, in whichever bowl is still showing bubbles.


Here's what I'd do after making sure the push rod is not adjusted too long. Freeplay is needed so it will let the piston come all the way back:


Find out which bowl is the one with air showing, to tell if it's front or rear. Then open one bleeder on that end of the car about 1/4-1/2 turn.

Lightly press down on brake more than 1/2 way but less than a full stroke. Now make sure that you go super slow on letting the pedal back up. Keep doing this 6-10 times and you should be getting a good clear flow out the bleeder. Close that one and do the other.

If you get no flow this way, close the bleeder and loosen the line at the master to do the same type of bleeding. Then if all the air gets out there and get only fluid there, then go back to the bleeder again.

 

Thanks guys, I got these two MC's from Napa and I don't want to keep going back there if it's not a bad master. It just seems weird to me that the reservoir for the front brakes does nothing until you really jam that piston in there. While the reservoir for the rears bleeds out just fine. I guess it's worth a shot to try to bench bleed again but I did for ever on the bench, then on the truck. Then hooked up the lines and bled brakes, went through two big bottles of fluid between the fronts and rears. It is pumping for the front brakes just not until you really get down in that bore, on or off the bench.