master cylinder question

[freebird01]

ok i got the dreaded mushy pedal....im 90%sure the master is junk and i plan on relacing it probably this weekend...

napa lists a 1 1/16" bore and a 1 1/8" bore.....i assume i would want the 1 1/8" bore so it moves more fluid and help with a firmer pedal..

what do you guys think?

 

[icanfixall]

Yes, the larger bore is what you want but... Does the parking brake set more than half way down? If so manually adjust up the rear brakes. The auto adjusters really don't work very well.

 

[BigRigTech]

I took a mushy 1-1/16 off my F250 and replaced it with the 1-1/8 F350 M/C....Works noticiably better.

 

[Mr_Roboto]

No doubt replacing a bad master cylinder with one of any diameter will get rid of the problem...

Increasing the master cylinder diameter will only reduce the pedal stroke, it won't make the pedal "firmer".

Having recently gotten back into the auto repair field, I've found that the "new thing" is mushy brakes, and the fix is often to use a pressure bleeder (not just a power bleeder) on the system. The steady pressure will push out air that no other method will.

 

[BigRigTech]

I just had a battle of battles with the F-inlaws brakes on his 95 Dakota 4x4....Finally got it fixed tonight.....It was dragging against the front wheels all the time....New calipers and M/C - no more dragging but now we had a mushy pedal....Bled and bled the POS with no luck, we tried another prop valve - same thing.....I called my uncle who's been wrenching for a living for 30 years - he was convinced the prop valve was air locked. We took the end of it out and a big burp of air escaped - problem solved and now it rolls free and stops great.....But it's still a Dodge.....hehe

 

[JPR]

wonder if the booster push rod is adjusted correctly?

If you unbolt the master cylinder, lay a straight edge across the face of the booster next to the two studs, the rod should be sticking out .995 inches