Ford Repair: brakes, wheel disc brakes, torino master

Question
Hi.  I have a 1966 Bronco.   It has been converted to 4 wheel disc brakes.  I was 4 wheeling and broke a rear brake line.  I replaced it and the master cylinder too beacause i heard that I needed a disc master cylinder.  I put a Torino master cylinder on it that was new because the Torino came with disc brakes.  Well, here is where I have trouble.  I have been attempting to bleed the brakes for a week and I cant get the pedal to pump up with pressure.  Ive tried gravity bleeding, vacuum pump bleeding and old fashioned friend pumps the pedal bleeding.  I can see the calipers moving but the pedal stays spongy and goes to the floor with no pressure.  Could I have a bad master cylinder or the wrong one?  Could there be a leak? I have the gm brake conversion up front with the cadillac calipers in the rear.  The rear calipers have parking brakes and Im sure they are adjusted correctly because the parking brakes work.  Could wrong line size be a factor because I put some 1/4 inch lines i had in the garage between the MC and the frame lines which are 3/16?  Do i just have to bleed more?  Thanks

Answer
Bill,

    Did you put a new brake pressure differntial valve on the Truck? It is located on the rearend,and when you go from drum to disce brakes you must change that valve. If it is not located on the rearend, you will find it located by the master cylinder. Did you bench bleed the master cylinder befor you put it on? The spongy feeling is air in the lines, you bleed passenger rear first, then drivers rear,passenger front,and then the drivers front. I hope this helps.


                                       Ken