I’m having an issue with my brake pedal not returning all the way causing the brake lights to stay on unless the pedal is pulled up the last 3/4” or so manually. (99 5.9l SLT) I originaly thought it was the brake booster as the seal around the rod coming through the firewall looked pretty bad & the rod was all rusty. Replacing the booster didn’t help. I tried adjusting the length of the rod in the booster that pushes on the master cylinder with no effect. I bled the brakes all the way around putting a full litre of new fluid through the system. There seems to be no adjustment to be made on the stoplight switch. How easy should the pedal move when unhooked from the booster rod? It would move fairly easy by hand but would stay in place wherever it was let go at. I’m wondering if the pedal is not moving freely enough & needs new bushings or if it’s a problem with the master cylinder? Thanks in advance!

I’ve oiled it a couple of times now with no change.

Yes, its the switch that activates the brake lights. Mine is not adjustable, or at least according to the manual it can only be adjusted once when it’s first installed.