Curing a "soft" brake pedal

[Bertam]

I recently replaced all four front wheel cylinders and both sets of front shoes on my car but have not been able to get a firm brake pedal. The pedal goes about 2/3 of the way to the floor and feels soft. If the pedal is pumped once (or twice on occasion), it then immediately becomes firm. It will stop, but the softness makes doing so not very confidence inspiring.

The car has unassisted, twin leading shoe brakes and all four corners have been manually bled several times (by two people using the pump and hold method) to no avail.

There are no visible leaks or air bubbles showing up when the car is re-bled and the shoes have been readjusted several times, yet after doing so the pedal remains soft on application.

Thoughts? Suggestions?

Andrew

[Mark]

Hi,
Check your mstr cyl very thoroughly, maybe install new seal kit when it's apart. They'll act good but allow a small amount of air in.
Just IMO,
MSH

[mascher]

The symptom can be either air in the brake lines or shoes that aren't adjusted properly. Try adjusting the brakes, both front and rear, so that they are all in solid contact with the drums. Check the pedal in this condition. If it's firm then shoe adjustment was the problem. If not then there is air in the system.

One thing you can try before rebleeding is to pump up the brakes so the pedal is firm. While holding down the pedal with your foot, jam a piece of wood or something between the pedal and the crossmember. Leave it this way for 24 hours. I don't know exactly why this works (and yes, that drives me crazy ) but it does often work.

If none of this works, it's probably air in the system. One technique for drum brakes that I used once was to remove all of the drums and shoes. Push the each piston of each cylinder in as far as possible and wire it in place with heavy iron or stainless steel wire. Once they are all wired so that they cannot move, bleed the brakes as usual and see if you get any air out.

Good luck,

Kelley

[Bertam]

Thanks for the replies Mark and Kelley - much appreciated. Please excuse the late acknowledgement on my part.

The issue seems to have been solved and came down to a matter of brake adjustment. I did re-adjusted them, drove the car a bit and then readjusted them again - rinse and repeat. After doing so four times they now seem to be were the pedal remains consistently firm.

Andrew