Street Rod = '46 Ford Coupe. Brakes were: Camaro drum rear, dropped straight axle with split wishbone front (kit from Chasis Engrg). Full size GM calipers, Granada power brake booster & master cylinder mounted up on firewall, no proportioning valve or additional residual valve(s), brakes worked fine!!!

Decided to update to Mustang crossmember & rack & pinion steering. Went to new stock Mustang spindles so rotors, & other hardware from straight axle wouldn't fit. Bought front brake kit from ECI = New rotors (full size GM), new ECI caliper brackets, new full size GM calipers, new rubber brake lines, new steel brake lines from master cylinder to front brakes (just for good measure). Attempted to bleed the existing rear system & new front system using 'push fluid out all 4 corners method', followed by pumping up & opening bleeders to expell air (old fashioned method). Bled until no air at 4 corners. Still didn't have very good pedal. Pedal went to floor when we started car & had the added force/help of the power booster. Took lid off master cylinder & saw "gelled" fluid floating on top of fluid in both ends of master cylinder reservoirs. Thought "moisture" or "sythetic fluid present" & we were using Dot 3. Flushed entire system to make sure everything was Dot 3-Clean, new fluid. Re-bled all 4 corners again until no air. Still pedal went to floor with little effort. Suspected master cylinder needed bled &/or was defective. Bench bled master cylinder, then re-bled all 4 corners until no air present. Still no pedal. Suspected master cylinder bad, although it was fine on the straight axle setup with esentially the same calipers, etc. However, since we saw the gell, decided to buy a rebuilt master cylinder. Same procedures tried on this rebuilt master cylinder & 3 more of them, same problem. Thought "since these are all rebuilds, they could all be someone else's problem", so bought a new master cylinder rather than the rebuilt (each one was same Granada power disc front drum rear as original). Each one bench bled fine, bled all 4 corners until no air, problem remained unchanged. Called ECI & was told we needed to add a "hold off" valve that holds off the front brakes momentarily to allow the rears to come on first & also told we needed a 10 lb. residual pressure valve for the rear. While thinking "it would be nice to have a pedal so that we would have symptoms like the front brakes coming in too soon" all the while knowing that before changing front ends the brakes worked fine without this stuff, decided to spend the money, bought & installed the holdoff & residual pressure valves as recommended. Benchbled master & bled system again, still no pedal. Bought "plugs" to plug off each end of master cylinder for experiments: plugged both ends of master cylinder = rock hard pedal (what we expected since the fluid couldn't go anywhere with both plugs installed, but thought it might tell us if master cylinder was bad), then plugged rear output of master & left front of master plumbed to rear brakes only (no front brakes connected). Bled system & had OUTSTANDING pedal & rear brakes even with motor running. Moved the rear brake line to rear output of master cylinder & plugged the front outlet = OUTSTANDING pedal & rear brakes even with motor running. Then tried front brakes on each outlet of master without rears hooked up & with each end of master plugged. Little or no pedal with either end of master used to try to operate front brakes. Called ECI again & gave them all this info, how we could operate the rear brakes using either end of master but couldn't get the fronts to work off either end of the master. For each test we re-bench bled the master & bled the system with which we were working until no air present. We even used 3 methods to bleed the system: old pump & bleed, vacuum bleeder device, & pressure device. ECI said we still must have air in front system & recommended "exercising" the front caliper pistons using a piece of wood thinner than the rotor width, then clamping the pistons back, removing calipers & holding them off the brackets to make the rubber lines "straight" to the calipers to help get air out. Spent this evening doing that. Rebled the entire system again, front & rear. Finished off our 2nd gallon of brake fluid tonight & we're in our 6th week of working on this off & on. Wishing we had never went to the Mustang front & lost our working brakes, even though all those front end :( updates look good if we could make the brakes work.

Are the tests we did on the master cylinder valid? Could we still have a bad master cylinder? Thinking strongly about seeking professional help, but don't know what they would do differently. Thanks for reading about this ordeal. Any ideas that we haven't tried or mistakes that you recognize & can point out will be greatly appreciated. Odie.

Take one of those clamps the you use to squeeze coolant hoses off so no coolant leaks and squeeze each front hose to a caliper, one at a time and see if you find your problem, it could be a defective caliper.

I think I would have to check each front caliper individually too.

Do the front caliper brackets move when you hit the pedal? Sometimes if the brackets aren't exactly straight, the pistons get pushed back too far when you let off.

Put a piece of steel between the pads on the fronts and try again (calipers off, keep fingers out). If you get pedal, either your brackets are moving or the rotors are.

Are the bleeders at the top of the calipers? Won't let the air out if they aren't.

Are your brake hoses expanding when you hit the pedal? How long are the hoses? They should be short, because hose grows more than steel tubing.

If all else fails, do as Fo_fdyfo says and don't worry about it, just make the horn louder :D

THat's all I could think of at the moment.

K

Thanks for the replies. We've done the test blocking off one caliper at a time & still same symptoms. The front calipers do move when we hit the pedal. You can see them move & clamp the rotor each time you pump the pedal during bleeding. However even after pumping the pedal up to 10 or 12 times & holding before releasing the bleeder, the pedal is only about 1/2 inch off the floor, then releasing the bleeder & the pedal goes to the floor where we close the bleeder each time. The bleeders are at the top of each caliper (we have them correct left & right). We tried clamping a plate narrower than the rotor in each caliper. Pumping moved them in to clamp on that narrower plate, but still no good pedal after more bleeding. Then we clamped back the pistons into the calipers like you would if installing new pads, to make the chambers in the calipers the smallest that they would be & left those clamps on during bleeding. Still no good pedal. The rubber brake lines from the frame to the caliper are about 14 inches long. They look good when turning the wheel spindles to extreme positions left & right (no tight or binding, just a little slack for suspension travel up & down). We are really thinking now that the test of plugging off the master cylinder at each output & having success with running the rear brakes off each unplugged end of it was not a valid test of the master cylinder. We are suspecting now that this 4th (& first NEW, the other 3 were all reman's) master cylinder is not valid. Since it is a Granada master cylinder & booster, the master cylinder has a 15/16" bore. After I did a little research, the full size GM calipers use a master cylinder with an 1.125" bore. I've found that the Corvette type power brake disc front drum rear master cylinder (late 60's thru mid to late 70's) have an 1.125" bore. If one of those would be compatible with the Granada booster mounting & depth of the c'bore in the MC piston (rod length coming out of the booster also needs to be right), then we may try that next. After getting 4 master cylinders from the parts store so far, they are "reluctant" to say the least, to exchange/warranty out another one, so I think I'm going to a diffent store to get the Corvette-type unit today & we'll try it tomorrow. I'm hoping that we can get the fittings to work between the Granada & the Corvette MC's without redoing the lines. Wish us luck.

I think you're having the same thought I was just thinking. The master cylinder either doesn't push enough fluid to energize the brakes or the pedal/booster does not push the master cylinder piston far enough to energize the brakes.

Peter

Well the story goes on! The Corvette-type master cylinder won't fit the Granada booster mount. I'm searching for a larger bore Ford master cylinder (larger than 15/16") that will fit the Granada booster. I'll start digging through the larger Ford vehicles for a larger bore unit & we can compare them to the Granada unit at the parts store to see if they'll mount. I still don't know whether we're on the right track with going for a larger bore or if we just have master cylinder #4 that is bad & we're unfairly judging the 15/16 bore as too small for the full size GM calipers.