No brakes on B2B

[John Zellmer]

Hi Guys,

I know this question has been asked and answered dozens of time, but I still can't get my brakes working.

Work done:

 New disc brakes on front, new master cylinder with 1" bore and 1.1 inch stroke mounted at frame level, new rear brake cylinders, all new brake lines, proper residual pressure valves, system pressure bled  several times using about 1.5 quarts of fluid - NO AIR REMAINS in lines.  I don't have the proper brake adjusting tool, but made one based on  example found in old forum post using PVC "T" fitting with steel rod and adjustable steel tab, shoe-to-drum gap is about 0.015 inches all around.

Problem:

 Brake pumping won't get more than about half pedal and goes to floor if foot pressure maintained . 

 

Would appreciate any suggestions.

Thanks,

John

 

[Jerry Roberts]

3 hours ago, John Zellmer said:

 Brake pumping won't get more than about half pedal and goes to floor if foot pressure maintained . 

By this description something is leaking . Possible loose line connection or even the new master cylinder . 

[lonejacklarry]

If you have no puddles under the truck  then it would most certainly be the "new" master cylinder.  Don't fall into the trap of thinking that all new parts do, in fact, work properly.

What is sounds like is the brake fluid in the master cylinder getting past the rubber parts that are supposed to generate pressure when the pedal is applied.  The rubber parts may be bad, may be installed improperly or the bore of the master cylinder may be scored.

Edited September 7, 2017 by lonejacklarry

[John Zellmer]

Thanks for the replies.  I agree that the master is leaking internally, but I had concern that the 1" bore was too small for the application.  Talked with Speedway Motors and they think the 1" bore is OK.  Shipping the old one back for a new one!

John