ON A SIDE NOTE:
Last time I had to tamper with brakes was before the Net had the mass of information it has. So accessing critical information was no easy task. Going to a library wasn't going to be much help with most things back-yard-mechanic [and similar] related (people who never get dirty aren't the best source of information on maintenance and repairs of things they rely on day to day).
I'd bleed many a brake system on cars and trucks from the forties through the sixties, then fought my 70's Fairmont and learned things had been changed. I knew I had to deal with new brake systems, but didn't know much else. Knowing what I know now, it's amazing I even got the job done, and did not become bald [from pulling my hair out].
Having just upgraded our 03 Ranger to a 78 GMC C15 step side, I knew it was probable there were going to be things to tend to, to bring the new truck up to snuff. One of the first, obvious things was, the E-brake was worthless. This called for adjusting the rear brakes, then the cable.
A peek under the carriage revealed a sagging cable, with the brake released. Too, it revealed no one, in 48 years (my 2017 was released in 2016), removed the rear adjustment access hole knockouts and replaced them with rubber plugs.
In light of the foregoing, and noting other indicators previous owners were no among the cream-of-the-crop when it came to maintenance and repairs, my suspicions went to that fresh brake fluid would not be a bad idea.
After reading a bunch, so I could lessen the chances of a repeat of the hassles I suffered bleeding the brakes on my 74 Ford, I learned about the hassles of dealing with what everyone, except a few, were calling the proportioning valve [explaining why bleeding the brakes on that old 74 Ford was so much fun].
I learned experienced backyard and professional mechanics used an inexpensive tool to lock the control device in the center position, while bleeding the brakes (picture below), so it wouldn't activate and compromise the ability to bleed the front or back of the system.
A few had to move the sliding valve back to center, before installing the bleeder tool. Presuming the control device wasn't a rusted mess (frozen in place on one side or the other), that was not an overly difficult task, once access to the sliding valve notch was gained.
After the nut was removed, it was indicated they could feel the position of the valve with a small screw driver, and use it to move the notch in the slider of the valve to center, before installing the bleeder tool.
If the valve wouldn't move, then it might be it suffered the perils of rust, and that problem needed to be addressed [including the fluid swap].
When bleeding was done, the tool is removed and the access hole closed again.
You must be registered for see images attach
