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Brake plungers,length

gick70

Sr. Member
Joined
Jan 30, 2011
Messages
544
So I rebuilt my new 77 rear to me,all hardware everything new,I didn't"t have brake piston plungers,purchased some,I now have a leak coming out from inside drum,I think I might have got too long of plungers,causing leaking! My question are all the plungers the same size between 66-77,what is the length I need for my 77?
 

B RON CO

Contributor
Bronco Guru
Joined
Jun 29, 2016
Messages
2,412
Loc.
Statesville, NC
Hi, I don't think there is a standard size push rod. I've seen master cylinders with deep and shallow bores for the push rod.
When you bolt the master cylinder to the fire wall or brake booster the push rod should be a close fit, but not pressing the piston. If it is not close enough you will have excess pedal travel. If the push rod is pushing the piston when you tighten the nuts it is too long, and is applying the brakes.
If you loosen the nuts and the master cylinder is being pushed out, the rod is too long.
I don't think this will cause a wheel cylinder leak. Check that out separately. There should be no brake fluid leaks.
Good luck
 

Broncomt

Full Member
Joined
Oct 4, 2015
Messages
187
Are you talking master cylinder rod or the rods in each end of the wheel cylinders?
 
OP
OP
gick70

gick70

Sr. Member
Joined
Jan 30, 2011
Messages
544
Never mind ,just another chink a nese part,replaced,all good!
 

jmangi62

Bronco Guru
Joined
Jul 28, 2013
Messages
2,469
I just got done adjusting the push rod for the master cylinder. I have everything brand new and still didn't have any brakes, they went to the floor with very little pressure. I was dumb founded, how could this be, I replaced all the parts, bled the system several times and still nothing, a little light went off and sure enuff, the push rod wasn't doing anything so we adjusted it and now I have brakes, whew, I was ready to stick a piece of dynamite in the engine compartment and run away lol. ;D
 

ntsqd

heratic car camper
Joined
Jan 30, 2005
Messages
3,224
Loc.
Upper SoKA
Hi, I don't think there is a standard size push rod. I've seen master cylinders with deep and shallow bores for the push rod.
.......
Good luck
The difference in short vs. deep m/c push-rod bores is that the shallow bores are for power brakes and the deep bores are for manual brakes.
 

B RON CO

Contributor
Bronco Guru
Joined
Jun 29, 2016
Messages
2,412
Loc.
Statesville, NC
Hi, that is probably a good rule of thumb, but not for every case. When I converted my 66 original fruit jar master it was shallow, so I had to sacrifice a 1/4 drive 9/32 short socket into the new dual master cylinder piston to take up the space.
It is helpful to spread the word so the next guy stays out of trouble.
It is good work practice to inspect every part, and if there are differences figure out how it is supposed to work. Good luck
 

ntsqd

heratic car camper
Joined
Jan 30, 2005
Messages
3,224
Loc.
Upper SoKA
That has been my consistent 40-ish years experience with every stock brake system. All bets are off when someone before me has made changes.
 
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