Ford Brake Problem

[Propflux01]

Replace a master cylinder on My Sis-in-laws 1976 Torino about 3 months ago. It was shot. Anyhow, all worked great, re bled everything,brakes worked fine. She calls me up today and says "no brakes'. I get the car, and she tells me that her front ( smaller) reservoir was empty, and she put fluid back in it, but still very spongy and the brake light is on continuously. I jacked up the car and there is not a drop of brake fluid anywhere on the wheel, front or rear, or anyplace. There was a slight amount that looked like it had leaked out the cover of the master, but none anywhere else. While I was pumping them, I did notice that on the proportioning valve, there is a little tit-looking thingy, almost like some sort of pressure relief valve, and it goes in and out with the pumping of the brakes, and sounds like a slight hissing sound to it. However, not a drop of fluid anywhere around it. i don't know if it is because there is air in the system or what, or whether it is supposed to even move. I had thought maybe I got a bum master, as the fluid is not clear, it is slightly brown, like fluid that has been in much longer than 3 months. When i originally bled the system after replacing the master, I used 2 quart bottles of fluid, to make double sure that there was not any contamination i the lines and such. So brings me to my question... Bad master? bad prop valve? where did the fluid go to? and help?

 

[alreadygone]

Prop valve is moving because of air in system. Small res is to rear drum brakes. discoloration is perfectly normal. As chances of defective new (or factory rebuilt) brake parts is pretty unusual I allways expect some other problem, but if you are ABSOLUTELY sure there are no external leaks, fluid's got to be going into booster. Small reservior emptying first is normal when m.c.'s going bad. If another,closer inspection finds no leaks, go ahead and replace MC again. Hopefully it's still under warranty. Please read and follow included insructions regarding bench bleed procedure.

Bob

 

[Propflux01]

I bench bled before install the first time, and that is what I had thoguht as well, but the inside of the booster is dry, and it does not appear wet around the input of the master, either.

 

[Propflux01]

Also, the small one emptied, the larger one did not lower its level.

 

[alreadygone]

Only two places to go, external or into booster. Have no idea how you determine booster is dry, removing hose and check valve to inspect is on wrong side of booster diaphram. Have you removed mc to check for fluid leak? As I stated mc developing problem will allways empty small resa first. She'd have to drive another several days without rear brakes before you'd start to see large res getting low.


Bob

 

[Propflux01]

yes, I removed it, as stated, that was the first thing I thought as well since I didnt see anyhting... I guess it is looking like a possible bad Master then...

 

[03cvpi]

You may want to pull the rear drums. A leak in the wheel cylinders can go for awhile before it begins to leak out onto the back of the tire. Also inspect the flex hose going from the body of the car out to the rear wheel assemblys, it may have been damaged or craked from old age. The fluid has to be going somewhere if not into the booster

 

[Propflux01]

I did just that today, dry as a bone. Replaced the Master, and seems to work OK. Time will tell...

 

[mechtech2]

A rebuilt [or even new] master cyl for that old car may have sat on a shelf for 30 years.
Rebuilds are notorious, anyway.