If the truck has four-wheel anti-lock brakes, and you let the reservoir run empty, you will need a scanner to command the computer to open two valves so those chambers can be bled. A simple trick to prevent the reservoir from running empty when you have a line open is to place a stick between the seat and brake pedal to hold the pedal down about an inch. Gravity will not be strong enough to pull the brake fluid past the rubber lip seals in the master cylinder, and you will not get any air in the ABS hydraulic controller.
Be aware that after about a year, crud and corrosion build up in the lower halves of the bores in the master cylinder where the pistons do not normally travel. Pushing the brake pedal to the floor runs those lip seals over that crud and can rip them. This typically happens when a driver is surprised by sudden leak, and when do-it-yourselfers and inexperienced mechanics push the pedal to the floor when bleeding with a helper and when running the pistons out of the calipers to adjust them. To prevent that damage, never push the pedal more than halfway to the floor. Avoid pedal-bleeding too. Most of us use gravity-bleeding with no helper.
Here is an article that provides some more information:
https://www.2carpros.com/articles/brake-pedal-goes-to-the-floor
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Wednesday, March 10th, 2021 AT 11:01 AM
