Brake Problem

[Eyegore]

OK guys I need your help. I replaced the brake master cyclinder and booster, still having a problem with no front brakes but now I stuck with the brake lights being on constantly. I have to disconect the battery cable to get it to go off. I know that my front brakes need to be bled, the whole system does after you replace the master cylinder, but I cannot figure out the brake lights ....... help I'm stuck.

Oh, this is on my 78 3/4 ton. I did bench bleed the cylinder prior to installing.

Thanks guys

[Pyrotechnic]

Sounds like the brake light switch on the brake pedal is malfunctioning. Not sure where it's located exactly as I've never had to change it, but look around under the dash on the arm of the brake pedal. It may also help to take off the metal access panel on the lower part of the dash right under the steering column. You will also have to take off the lower plastic trim piece of the dash bezel thats directly under the steering column before the access panel can come off.

EDIT: I'm assuming when you say brake lights, you mean tail lights right? Or do you mean the "BRAKE" indicator light in the speedometer?

[Eyegore]

Correct the brake - tail lights

[grinch4om]

bleed it then chase the light switch, pedal may be drooping and turning on switch. pull up on the pedal and see if the lights go out and if there is any play

[marvxyz1]

I think your brake light switch is being popped out of position when the master cylinder rod recoils out of mastercylinder, after you let off the braskes I've had that problem and replaced master cylinder. Didn't help!! Taped the switch into posttion with duct tape, and held for a while. Got to love that duct tape!! I tried to tighten a nut on the threaded portion of switch. I don't think it was a very good idea,Since I've been having a lot of. brake problems. (dragging brakes)since.

[Ivan D.]

Brakes do not always need to be bled if the master cylinder is replaced, if you are careful only the master cylinder needs to be bled. Also when you replaced the master cylinder the new one might have a slightly deeper hole for the booster rod, as a result of which yer pedal sits slightly lower than before and trips the brake switch. If you have air in the lines you need to bleed the brakes at all 4 wheels, then readjust the brake light switch.

[marvxyz1]

I was wondering if you could just cut a small portion of the rod off and dress it up. I've been dealing with the brake light switch problem or some time. Taping the switch in position with duct tape seems to be the best solution for me,though.

[lurch115]

as far as the tail lights staying on...i agree with everone else....look for that switch and see that it is being fully pushed in...(or fully released...its been too long since i've messed with one to remember what side of the pedal the switch is on)

as for the front brakes not working... first off....BLEED THEN, and second off, have you checked to see that the calipers aren't bad???? i can't tell you how many times i've pulled a caliper off (old and new) because the piston wouldn't move in or out....