[Bob B.]

When you say dual master cylinder, do you mean there are 2 lines coming out of the firewall mounted master cylinder? If so those systems often have 2 boosters. If there is just one line coming out of the firewall mounted master cylinder and it goes to one booster, that is a single system. That is what most C-50's had. The way to bleed the single system is master cylinder first, then booster, then right rear-left rear-right front-left front wheels. Then master cylinder and booster again. You may have to do this multiple times, you will loose a lot of brake fluid and you have to be careful not to let the master cylinder run dry. It is quicker to use a pressure bleeder if you can get one.

Now for the disclaimers:

Do not mess with medium/heavy truck brakes unless you know what you are doing. Seek professional help if in doubt.

Do not bleed the brakes in an old truck that has been sitting and attempt to drive it unless you pull all the drums and thoroughly inspect the wheel cylinders for leakage. Also inspect all lines, master cylinders and boosters. Check for vacuum leaks and be sure the booster is functional.

Do not attempt to drive the truck unless you are sure of the condition of the brakes. Also make sure the emergency brake is functional. If a single system has a leak it is surprising how quickly the brakes will cease to function.

Don't mean to be offensive, just don't want to see anyone have an accident. Over on one of the Ford forums some clown lost an F-600 down a hill after he messed with the brakes! Luckily he didn't kill himself or someone else.