new brake cylinder and new problem for 521

[datson4life]

i got all drums, after i installed the new master cylinder the issue started

 

the brakes get stiffer and stiffer until they just lock up, i bleed it a little bit and im good for another day, anybody had this issue before?

they have been bleed and adjusted a few times

 i did have a broken spring that has been replaced in the front driver side drum, but issue continued

[datzenmike]

Master cylinder push rod is not adjusted properly. There should be a couple of mm or 1/16" of brake pedal play before the pushrod begins pushing on the master.

 

Near the top of the brake pedal is an adjustable master push rod and clevis securing it. Remove the clip and the pin from the clevis and you can now loosen the lock nut and turn it in or out to adjust the throw. Set for 1/16" to 1/2" of pedal play. Tighten the lock nut and clevis pin

 

DO NOT FORGET TO INSTAL THE COTTER PIN IN THE CLEVIS PIN.... VERY IMPORTANT!!!!!

 

 

 

What's happening is, the master piston is not fully returning to rest when the brake is released. If it does not return fully it can't release all the pressure in the lines ahead of it. Each time you use the brakes more and more residual pressure is trapped until the brakes are locked.

[banzai510(hainz)]

yes I had this proplem before.

 

first is when you installed the brake master was the shaft fully extended. I have swapped 3 new brake masters and every one the threaded shaft is too long which pushes on the pedal  thus pushing it slightly in when its mounted on fire wall.  So what I do is put a nut on the treaded shaft and cut a certain amount off the threaded end. then pull the nut off as it cleans up the threads then put your yoke or whatever you want to call it back on.

Then reinstall and see how it fit and hopefull your pedal isnt putting  preload on there.

 

OK if you did that correct(shaft is fully releasing from the master) and it still pumps up then its a bad Master as most are made in Taiwan.  My last Rebestos boxed taiwan part did this but it was maybe a 1yr old.  all 4 brakes would get hot. I would release the rear bleed screw and would be good for a few days or maybe a day.

 

I swapped master cylinders and was OK after that. The master i have in there is a Dorman brand Taiwan unit. Its a cast iron pc.

 

use a brake nut wrench and I put antiseixe on there also. Make sure not to strip or x thread .

[datson4life]

thanks, i will try that later, i do remember the shaft being pushed in a little when installing cause it was a bit too long

[datson4life]

i shortened the brake light switch quite a bit, it was sticking a little too far and it seems to be okay now, i will drive for a while to be sure, now i have an electrical issue, the flasher/ reverse/meter fuse keeps blowing

[glorydime]

Man I've been experiencing this exact problem, the rod is too long no matter how much I adjust the rod it will not fully release. I'm going to cut that rod tomorrow.