Brake problem

[Clive]

72 SIII 88'
Fitted brand NEW brake shoes and drums all round . New fromt cylinders.
Bled system - nice and firm.
Test drive and the pedal suddenly has massive travel ..air? Pumping firms it up only for that braking episode.

Rebleed and check for leaks...no air, no leaks. Servo new (a few months back).
Test drive and the pedal goes way down again....repeat...

So when engine off, brakes really nice and tight. Do not even go soft over night. No visible leaks. When sitting with engine idling, brakes appear nice and firm, BUT when I drive, and apply the brakes they travel way down. They stop the truck pretty well, but this is not how it should be.

Of course brakes did not have this issue before I changed them out...

Many thanks for any comments!

[a109]

How do you have the upper brake shoe springs connected? They must NOT connect between the shoes. They go from the leading shoe to a peg on the backing plate.

John

[singingcamel]

easily to mount the shoes incorrectly, check the manual..as stated above.
also , you may want to either power bleed or( gravity bleed?i heard it worked)
also follow the bleeding sequence closely,farthest to closest to the master cly.
air is still trapped and can be a bugger to get rid of.

[gudjeon]

You didn't mention adjustment. I know brake shoes can seat in and need adjustment once in a while. Maybe they seated in being new and caused excessive pedal travel? Just a thought.

Jon M.

[Clive]

I have springs going from shoe peg to the backing plate peg...and I think set up correctly! Have reset them as well using the adjuster. they definitely work, but are really soft most of the time. they also judder if breaking heavily but everything is tight! I will rebleed this w/e.

[Jeff Aronson]

Hmmm...I have a II-A and I know there are some differences, but you've provided some hints that have triggered memories of many brake jobs.

I once replaced shoes and even drums on my rear brakes, and have done the fronts. only to discover that the brakes were worse than before my repair. I happened to be near Rovers North at the time. Mark Letorney took a look at the car and insisted that I adjust the brakes again. When I did, the pedal hardened right up and the brakes worked fine.

I've also put the spriings on wrong before, so double check your work. If the springs came with the car and you've had it for a long time, they may not have the necessary tension. I replace them every few years, too.

I have also screwed up the springs on brakes before. So jack up each wheel and turn the adjuster until you can't spin the wheel. Then back off the adjuster and try it again. See if you have a firm pedal.

A hard pedal at rest, or with the engine off, is deceptive. There's not much for the brakes to do at rest. When the car is running, your power assist permits you to push down harder on the pedal, and thus some movement.

Try taking a brake clamp to the hose to the rear brakes. Do you now have a firm pedal? If so, the problem is in one of the rear brakes [wrong assembly or bad cylinder].

Also, did you check the drums for the interior diameter? You can't shave much off before they need replacement. The brake judder you describe implies that your drums are not round any longer. When they're new and have the proper tolerance, you really have to squeeze in the new shoes and back off the adjuster to get the drums over the shoes. If they slid right on, the drum might be your problem. It's an easy fix, too.

You might want to check that the wheel cylinders aren't leaking at the bleed nipple or at the caps inside the drum. Any leak there would show up as a weak pedal, but you wouldn't lose much fluid.

If you truly had a good pedal, if long travel, before you replaced the shoes, your master cylinder should be fine. Still, if it's old, it may be leaking past it under load.

Good luck!

Jeff

[jp-]

If the springs came with the car and you've had it for a long time, they may not have the necessary tension.

You mean these springs lose their tension!?!?

Sh!t, I reused my 40 year old ones.

They still looked good to me... Especially after I painted them...