Brake Problem

[Bob & Chris]

Son and I purchased a Series III, 88 inch, with bad brakes. It has 10 inch drums all around. Pedal goes almost to floor, but when pumped up, will stay up until you release it, then pedal next time will go to the floor again. Master Cylinder has been replaced as well as all four wheel cylinders, shoes and springs.  All bleeding good and adjusted shoes, no leaking and flex hoses good, drums look new. We used master cylinder PLC 753, and two sets of PLB 535 and PLB 536 wheel cylinders. All parts removed looked like what we put on, all four wheels look the same, with one adjuster per wheel. The car was refurbished 7 years ago and looks like they used what ever parts they had. The car's paper work said it is 1982, but don't think so. One question, what is different in the wheel cylinders PLB537 and PLB538 to the 535 and 536 that we used? Any idea on why the paddle goes to the floor?  We have run out of things to try, and any help would be greatly appreciated.  

[mearstrae]

If there are no leaks, and no air in the system, you probably got a bad master cylinder (or the wrong one). I've seen brand new masters with the internal seals in backwards...

[roverp480]

First thing to check is that the shoe pull off springs are fitted correctly , The trailing shoes just have the one spring at the bottom connected to the leading shoes, . The leading shoe has the extra spring between the post on the backplate and the one on the shoe where the adjusted rubs. If the springs are fitted incorrectly it will give the symptom's you report . I fitted the top spring between the two shoes back in 1968 on my first Land Rover and had exactly the same problem as you. This is not a very good picture but you can see the top spring is connected to the post on the backplate and the Left hand leading shoe. The bottom spring is just connected between the two shoes.
13598

[cedryck]

10 inch Rover brakes are notoriously prone to poor spring set up as RoverP480 has stated, start there with checking the springs are set up right. Then insure that air is totally removed from system, even a little bit will give a poor pedal. Some folks here have reported that after bleeding at the wheels, jack the front of the truck up, (in an attempt to make the master almost horizontal, and cracking the exit pipe while having someone press pedal and see if any air is trapped in the bulb end). Also insure that the wheel cylinders are sound and not leaking or stuck closed or open. I have had that happen.
Also look into the Green bible for the set up distance from the floor of the cab, to the recessed pedal height. Its easy to do. Look and inspect for leaking connections, then read about setting up the shoes against the drums. Spin wheel and adjust cam to that the shoes are rubbing and close to drum it takes time to get this "feel", but it is important, a good brake shop or garage can make sure that your drums are round if you suspect that they are not.
I read that some bloke in England parked his rover on an uphill slope over night, (air rises) and then was able to expel some trapped air in the master the next morning with the procedure I described before. Best of luck, cheers.

[roverp480]

Just found a better picture 13600

[tmckeon88]

Son and I purchased a Series III, 88 inch, with bad brakes. It has 10 inch drums all around. Pedal goes almost to floor, but when pumped up, will stay up until you release it, then pedal next time will go to the floor again. Master Cylinder has been replaced as well as all four wheel cylinders, shoes and springs.  All bleeding good and adjusted shoes, no leaking and flex hoses good, drums look new. We used master cylinder PLC 753, and two sets of PLB 535 and PLB 536 wheel cylinders. All parts removed looked like what we put on, all four wheels look the same, with one adjuster per wheel. The car was refurbished 7 years ago and looks like they used what ever parts they had. The car's paper work said it is 1982, but don't think so. One question, what is different in the wheel cylinders PLB537 and PLB538 to the 535 and 536 that we used? Any idea on why the paddle goes to the floor?  We have run out of things to try, and any help would be greatly appreciated.  

Hi-

You might check to see that the large pivot pin that the bottom of the brake shoes rest on is not broken away from the backing plate. It can break but not fall off and creates slop in the brake linkage that adjusting will never take up. I have that problem for years in my 1969 88" and I could never get the brakes adjusted well; a mechanic in Springfield, MA finally spotted it and I replaced the backing plate and it was like a whole new brake system. It might be on any of the four wheels and would cause a problem for the whole system.

Tom

[jimrr]

cedreak and mearstrae probably nailed it. i'd vote for something in the master cylinder, i just went thru that with a old f-250, it was hard to get the air out and yes, i've seen the cups in backwards too but usually if it builds pressure by pumping and then won't again a minit later you've usually compressed the air quite a bit before it left the area but it soon returns. the ford encourages the master to be bled on the bench, it made all the difference but i never had to do it on the Land Rover ....