Expert: Sean Halliday - 11/4/2008

Question
Hi. My 1993 Suzuki Sidekick brake pedal had been creeping to the floor for a few weeks, then abruptly failed to "front-brakes only" mode. I replaced the steel brake line that had failed, then the master cylinder. The rebuilt master cylinder had a large yellow warning tag, "Do Not Bench Bleed this Master Cylinder!" Although I had never heard of such a thing, I followed the special instructions as well as I was able.
Unfortunately, nothing in this vehicles brake system looks like the Haynes manual. I bled everything in a standard way, but have not been able to get any pedal back. I still have front brakes with the pedal at the floor, and the emergency brake functions well with the hand lever.
There is some kind of a hydraulic feedback loop running from  the proportioning valve to the master cylinder; I get little  or no fluid when I try to bleed that fitting. My question involves the proportioning valve. There is a rubber plug on the firewall end that has a hole under it. Am I supposed to manually reset the valve somehow, as I had to in my old Plymouth? The brake failure sensor is mounted atop this device. Or does it sound as though I might have mucked up the master cylinder install? Thanks for your time!

Answer
Bench bleeding the master is common as i have done so an many units.I dont know how you installed your master but there is really only one way to put it in.With all the parts in place,start to bleed the rear first usually furthest wheel away from the master then the other rear and then passenger front,finally drivers.Use someone who can pump the pedal slowly is the key here all the way up and all the way down.Tighten each bleeder and repeat until the pedal is getting harder.As for the proportioning valve,if it does not have a bleed nipple,then you dont have to bleed it as i have never seen any valve that needs bled other than the calipers or wheel cylinders.10 pumps per wheel and tighten should be ok.