Hi everyone,

I'm in front of a problem that's been ruining my life for the past few months (I only get to come home and work on the car every now and then...).

I changed : M/C, brake calipers and drum brake cylinders.

I bled and retightened everything more times than I can count but I still have this very long pedal stroke and very very weak brakes (it won't stop the car straight away even if going 20MPH).

AND! it seems like the pedal is sucked by the assistance. I just slightly touch the pedal and it's sucked to the floor (though not braking much as I stated earlier...). I have to make it go back with my foot!!!

Does anyone have any idea what the h*** is it all about?

Thanks a lot for your help!

Marc

what type of car is it? year and model,do you have power brakes? did you bench bleed the master cylinder before you installed it? are your front discs single piston?

Is it the original braking system or have ther been other up-grades or changes besides the Master Cylinder?
DD

I had the same thing happen. The power brake booster diaphram was bad.

Hi everyone,

Of course the basics...
So it's a '67 Dart with Kelsey hayes (4 pots) brake discs upfront and rear drums. The M/C is a dual line as it's supposed to be. And I do have power brakes.

No other upgrades, replaced a few brake lines but that's all.

About the bench bleeding, I did as written (well almost) on the manual that came with the M/C which means I put the plastics taps on the M/C, put it on the car, filled it and then pushed the pedal until brake fluid came out (loosening the taps a small bit).

I reckon this is not the perfect procedure but I did not have any spare lines to do the small return line that goes into the reservoir (right procedure right?)

Thanks for your help,

Marc

P.S : what about the diaphragm? Should I open this up?

I used to be a professional mechanic on vintage british and italian sportscars, and that used to happen quite a bit to me. The two main causes I have found are, 1: loose fitting... go back and dry the brake fluid off of every connection with brake cleaner and rebleed.. look for wetness.. 2: the supergeniuses who rebuild the cylinders occasionally put the seals in backwards... Also, check to make sure your drums are adjusted properly, as the rear brakes set your pedal height