Long story, please bear with me. Disc/drum Power brakes on my '55 Victoria. I was returning from a drive and my brake pedal started going down/getting soft. I was close to home so I drove on in. When I went to check the brake fluid I saw brake fluid on the brake warning switch and paint bubbled where it had dripped on the inner fender. The large chamber of the master cylinder was out of fluid. ***uming the switch was the culprit, I ordered another and installed it. The brake pedal seemed ok, so I closed it up and left it. The next time I drove it I noticed slight braking was OK, but firmer pressure was met with a rock hard pedal and no increased braking. The rear wheels , the ones fed by the once dry MC chamber, would slide a little if I stood on the pedal. I bled the brakes all around with no change. I'm thinking the front chamber that feeds the front brakes is partially locked up. I disconnected the line from that chamber and had someone mash the brake pedal. It would produce about a tables**** of fluid and the brake pedal would get hard. Strange thing is this happened when I found brake fluid on the warning switch, and in the process of all the bleeding, etc, I left the switch out of the combination valve and it didn't leak out of that port. I know I could replace the master cylinder/combination valve ***embly and maybe fix it, but would like to know for sure the culprit. I know that is a lot to digest, but I appreciate any wisdom you might have.
Is the front line new? Maybe the vertical loop has air trapped? The back line being horizontal wouldn't have that issue.
The car was built in 2011, I bought it 6-8 years ago. Nothing done to the brakes since I had it except for bleeding them since all this started. There is a line running to each front caliper from the front of the combination valve.
Did you bleed the master cylinder by itself, just like you would do a bench bleed. Not saying this is the problem, but dual master s/b bench bled before hooking up to the system.. Losing all the fluid in one chamber is the same, to me, as starting with a new master. if there was some fluid left in the dryer chamber, than this might not be necessary.
The chamber that was dry was the rear brakes and they are working fine. That said, I have taken a front wheel off and had someone apply the brakes. I put a 2 foot pry bar under a lug bolt and across the hub and could not move the caliper. I realize this isn't scientific, but the front brakes are holding some. If I really stand on the brake pedal the rear wheels will slide a little just before it stops. In a simulated panic stop, the car comes to a slow stop as the rear wheels slide.
The large chamber should feed the front disc brakes, small chamber the rear drum. If the large chamber was dry you were stopping on the rear brakes only, and drum brakes take much less fluid pressure to operate. This could explain why you can get the rear wheels to skid but not the front. There was also a procedure to center the valve in the combination valve if you removed the switch or one 1/2 ran out of fluid. I suspect air in the front brakes and a combination valve issue preventing the front brakes from getting enough pressure. Google recentering the brake combination valve. Mark
Thanks for the input. I took the line from the master cylinder loose at the input to the combination valve and the master cylinder still gets hard half way down. I have a new cylinder to install. If that doesn't fix it, I'll go to the combination valve.
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