Odd brake problem

[Guest GaWajn]

Hey guys,

A friend of mine is having an odd problem with the brakes on his newly restored Austin Healy. It has front discs and rear drums. When he is in the shop and the system is bled ... he has a hard peddle, but as soon as he starts driving ... when he hits a bump in the road, he has no peddle. He has changed many of the parts ... up to three times. I was wondering if anyone here has had a similar experience?

[Pete O]

Is he finding more air in the lines when he bleeds it after hitting a bump?

[Bud Tierney]

"...he has no pedal..."...D'you mean absolutely none??...drops to the floor, only resistance is return spring??...won't pump up any pedal at all??

In line with Pete's question, is any fluid missing, or is all fluid dumped??

Is this a conventional non power system where brake pedal works master cylinder, master cyl pressure activates wheel cyl systems, or does this have some AH idiosyncrasies of design or const'n???

Has complete master cyl been replaced??

Weird!!

[Guest GaWajn]

Complete system has been replaced ... most hydraulic parts have been replaced twice to try and isolate this problem.

The peddle goes to the floor ... no brakes ... just the return spring ... no fluid dumped ... non power brakes ... pumping will not return brakes ... very weird!

The rear drums have an odd system. The cylinder in the drum housing does not pressure both shoes the way we are used to on american cars, it is a system of levers that actuate the shoes from the cylinder that acts as a hydraulic piston that only applies pressure in one direction. The mechanic that is trying to fix this problem is very experienced ... and might be the best mechanic I know. He build racing engines, has been restoring cars to a very high degree for a long time. It has to something that is specific to this particular British design, and not some basic hydraulic brake problem.

The request for help here was a shot in the dark ... maybe someone out there with experience with the old Austins knows of this type of condition and can point out the cause. I am certain that the mechanic will eventually figure it out ... but I thought I might ask here in the hope that this was a known condition, with a known fix, so that I could show off the knowledge of my AACA contacts

Your input is appreciated.

[Guest Al Brass]

I can't think what might bew going on but there is a clue in the road bump and then no pedal. Check the pedal free-play.

Al