I am in the process of resurrecting a '66 Ranchero that's had a rather hard, neglected life. One of the many jobs involved completely replacing ALL of the brake stuff, from one end of the vehicle to the other. It has the 2.5"X 10" front drums, and 2" X 10" rear. New parts include drums, shoes, wheel cylinders, hardware kits, self adjuster mechanisms, all metal and rubber brake lines, fluid and master cylinder.
Originally, because I had a NOS one, I installed a 'single' master cylinder. New brake lines connected the one outlet port to the rear brakes, and the other port was routed to a Line Loc, and from there went to each of the front brakes. Problems began when we attempted to bleed the system. I did not 'bench bleed' the master cylinder because I've never needed to do that previously with this type of cylinder.
Starting at the rear end, the longest line was bled first. Only minimal 'spurts' of brake fluid came out, but eventually the air bubbles stopped. Next came the other rear brake (with identical results), and then the fronts. The passenger side was bled first (longest) and then the driver's side, again experiencing only minimal spurts of fluid, usually right near the end of each time the brake pedal was depressed to the floor.
When the bleeding was finished, and the master cylinder topped-up again, a press on the brake pedal revealed no resistance...the pedal could easily be pushed all the way to the floor. There was no evidence of any leakage around the master cylinder, nor at any of the four wheels. The master cylinder stayed full of fluid. It appeared that the master cylinder was defective...that pressure was leaking past the piston seals or something, so that it could only push some fluid out when there was no resistance, due to the open bleeder screws. As soon as the system was sealed up, it couldn't generate brake pressure.
At this point, I decided to replace that single cylinder with a 'new' Raybestos PG MC36222 cylinder...the dual-bowl one listed for '67-'70 Fords with drum brakes. This cylinder has same-sized bowls both front and rear. This time I followed the manufacturer's 'bench bleeding' instructions...but it did not go exactly as they indicated it should. They suggested that after clamping the cylinder in a vise (level) that the bowls be filled with new brake fluid, and you were to wait for fluid to begin dribbling from the outlet ports. Once this happened, you were to install the thread-in plugs they had supplied, and continue with bleeding. The problem was that after waiting more than ten minutes, no fluid was dribbling out??
I decided to try 'gentle' pressure on the pushrod, against the piston, partially depressing it maybe 1/2". A bit of fluid spurted out of the front port, so I installed the threaded plug there, and tightened it as Raybestos instructed. Applying more light pressure on the pushrod finally got a spurt from the rear ports, so that one too was plugged and tightened. The instructions then told you to press on the pushrod to depress the piston about 3/4"-1.0" several times, until you felt considerable resistance, and could only depress it about 1/8" total. I got to where it would only depress about 1/4", and figured that was as good as it was going to get. Leaving the plugs in place, I took the new cylinder over to the car.
New lines were again bent to connect things. Since I had no information that it really mattered which bowls was connected to front or rear brakes, I followed the usual for disc brake cars and ran the rear bowl to the front brakes, and the front bowl to the rears. I used proper reducers in the cylinder ports to accommodate the 1/8" fittings on the 3/16" brake lines. The brakes were again bled, following the long-to-short procedure again. This time, after some bubbles, there were stronger spurts of brake fluid from the rear brakes. The front ones however still seemed weak. When finished, I was both disappointed and frustrated to find that the pedal again went to the floor! It was pumped a half-dozen times, but continued to go to the floor each time.
At this point, I decided to reverse the lines, running the front bowl of the master cylinder to the front brakes, and the rear bowl to the rear brakes. Again, the pedal would go down to the floor, but did encounter some resistance for the last inch or so. A careful check of all lines, fittings and wheels still showed no evidence of any fluid leaks.
Deciding to try another tack, I removed and plugged the front brake line from the master cylinder, leaving the rear brakes connected to the rear bowl, and tried the brake pedal again. Ah-hah!...a firm pedal about halfway down to the floor! Just to cover all the bases, I removed the rear brake line from the rear bowl, plugged it into the front bowl, and plugged the rear one. Again, the pedal would go down a couple inches and then get very firm. Hhhmmm??
Wondering now how both ports could produce a firm pedal, as long as only the one pair of brakes was connected, I decided to join them. A short line was bent to run from the front master cylinder port to the rear port. This produced a 'rock hard' brake pedal that could only be pressed down about an inch. So it seemed that the master cylinder was indeed capable of generating fluid pressure, and that there were no internal leaks.
Removing that jumper line, I now connected the front brakes (with the Line Loc) to the front port of the master cylinder, and plugged the rear port. There was some resistance, but the brake pedal would still sink to the floor.
I moved the front brake line over to the rear port on the master cylinder, and plugged the front one. Similar results, with some resistance to pressing on the pedal encountered, but it would go down to the floor.
Sure now that there was something about the front brake setup creating the problem, I decided that the Line Loc must be the culprit. I removed it from the vehicle, and got an Aeroquip 3-way, reverse flare fitting. This connected the two front brake lines, and a short line over to the master cylinder port. Same results...the pedal would go to the floor, with some resistance, when pushed. I moved the front brake line to the other port on the master cylinder. Same results! Aaarrgghh!!
So all brake lines were removed from the master cylinder, and a short line and rubber hose were run to a collecting bottle. The brake pedal was slowly pumped (keeping the lower end of the rubber hose submerged under brake fluid so no air could enter), and after some 'minute' bubbling strong spurts of brake fluid were seen. That port was plugged, and the bleeder line and hose moved to the second port. A similar process showed it to have virtually no air, and good spurts of fluid were seen.
At this point, the bleeder line was removed and the rear brake line was threaded into that port. The other port remained plugged. When the brake pedal was pressed, considerable resistance was felt, and the pedal went nearly solid about 1+1/2" down! Thinking that the problem was finally rectified, I reconnected the front brake line to its port, and again pressed the pedal. It went all the way to the floor!
Thinking that the rear brakes were now working well, I again tried bleeding the front ones, only to have the same 'weak' spurts of fluid appear in the collection jar. The brake pedal felt and acted the same, going right down to about an inch off the floor before encountering any real resistance. Switching the front brake line to the other port on the master cylinder, and bleeding them again, produced the same results. Huh??
So the situation hasn't changed, even after removing the Line Loc and replacing it with a solid mechanical connection...the rear brakes are firm and hold fast no matter whether connected to the front or rear bowl of the master cylinder. The front brakes don't seem to work from either. If all the brakes are connected as they should be, the pedal goes to the floor, only encountering any real resistance in about the last inch or so. There is no evidence of brake fluid leaking at the master cylinder, anywhere along the steel or rubber brake lines, or from the wheel cylinders. It's as if with all the brakes in place the master cylinder can't develop any pressure. When you press the brake pedal, you get the usual 'geyser' of fluid spurting up out of the front bowl.
Needless to say, I'm extremely frustrated, confused, and fresh out of ideas what to try next! I'd appreciate hearing from anyone who has fought a similar battle, or perhaps knows what is at fault here. Thanks for listening.
