Triumph Repair: TR4 Brakes, brake pipes, rear brakes

Question
I just installed all new brake pipes, new wheel cylinders, rebuilt the mc and installed new brake shoes and pads.
bleed the brakes multiple times and still the brake pedal goes to the floor.
Ther are no fluid leakes. The front calipers have a little drag when I spin the wheels so I don't think the problem is there. The adjusters on the rear brakes are set to just a little drag also.
Any ideas on how to fix?

Answer
Hi Rick,
Even in the dealerships we run into such at times when the whole system is rebuilt.
If you bled in the correct sequence. Left rear first, right rear, Left front and right front last. Then you may need to do what we had to at times to isolate the problem.

I purchased an assortment of bleeder valves from a local auto parts store and in the assortment I found a bleeder valve that fit the line hole in the master cylinder so I removed the line and put the bleeder valve in place of the line and pumped up the brake pedal and used the bleeder to get all the air out of the master. This gave me a rock hard pedal which is a test of the master cylinder.

Then I replaced the line and removed the rear line from the 5 way union over on the lower right front frame area. Installed the bleeder valve in the union and bled both front calipers and the bleeder on the 5 way union. This tested both front calipers. You should be able to get a hard pedal here too. If not, have someone pump the pedal hard up and down while you look with a good light at the each front disk in relation to the caliper. There should be no movement. If you see movement it means on of the pistons is sticking.

If you can't get a good hard pedal but see no movement, do this. Remove the brake pads on one caliper at a time and put in place of the pad either a worn thin pad or anything hard that is thinner than the new pads and pump the brakes a few times. This pushes the pistons out a little. Now pry each piston back into it's cylinder just enough to force the new pad in. If you pry it too far and the new pad slides in freely you need to do it over. The objective is to have a slight preload on the pads by the pistons. When you have done this to both sides check the pedal again. If you then have a good pedal then you can connect up the rear brake line and it should be ok then.

Since there are no retracting devices to pull the brake pads away from the disks, the manufacture uses the flexing of the seals to pull the pistons away from the pads. When you install new stuff the seals get flexed in the wrong direction and it takes more fluid to move all the pistons up tight so by placing the flex in the opposite direction you have enough fluid to operate the brakes. As you drive the car it will self center and the problem should not return.

Some caliper bleeder valves are the same threads as the master cylinder line hole so a bleeder from a caliper can be used.
Howard