Triumph Repair: Bleeding Brakes TR6, brake master cylinder, bleeding brakes

Question
Howard,
I'm restoring a 1972 TR6 and I've replaced a brake wheel cylinder on one wheel, replaced the seals in the PDWA unit(including the new piston that came with the rebuild kit)and several brake lines.  I positioned the piston on the PDWA so it was centered and you could see through the connections for the front and rear brake lines implying that brake fluid could flow to both the front and rear brake lines. After installing these parts, I filled the brake master cylinder with Dot 5 fluid and secured the top.  I had some one depress the brake pedal while I bled  the nipples at the front and rear brakes.  What I found was that there was no fluid flowing from any of the bleed nipples. The master cylinder was still full of fluid. Prior to adding the mentioned parts, I had bled all 4 brakes successfully.

Is there an air lock that is preventing the fluid from reaching the brake wheel cylinders?  Should I be checking something else?  I had my helper hold the brake pedal down a number of times while I opened and closed the bleed nipples. I was also using a bleed hose and bottle.

Any help would be appreciated.

Thanks

Kim

Answer
HI Kim,
You need to bleed the right rear brake first and when your helper in pushing on the brake pedal he/she needs to tell you when the pedal hits the floor when you open the bleeder valve so you can close the valve before they lift their foot. And when they pump the pedal back up they need to use slow long strokes. Left rear second, right front third and left front last. The PDWA unit is just an electical switch that warns the driver when one half of the brake system is more firm than the other and it should not hinder bleeding.
You should by now have some pedal feel. So rebleed in the correct sequence.
If you can pump up a fairly good pedal and hold light pressure for several minutes the master cylinder is probably ok. However if you can pump up a fairly good pedal and if you hold light pressure and the pedal slowly goes down you either have a leak or your master cylinder is bad. If you repeatedly bleed and get NO air bubbles in the bleed line but you have a very soft pedal, you have too much movement somewhere. The standard method to find the movement is to run one rear wheel brake adjuster up tight as you can to lock up that wheel and check the pedal again. Then do the other rear wheel the same leaving the first locked up. If you still have a very soft pedal leave both rear wheels locked up and take a bright light up to a caliper and look closely at the relation of the disk to the caliper and have someone pump the brake pedal while you watch for ANY movement. If you see movement then probably one piston is stuck and not moving and the other is pushing the disk over to meet the other brake pad/piston. Check both sides. A stuck caliper piston will make the other piston displace more fluid than the master can supply in one stroke. Don't skip any of this, every step is very importent.
Let me know,
Howard