Rebuilt the master cylinder, which means I found a source for the rubber seals and replace them. Master worked fine and still does, but the brake lights started to come on after a few minutes. Pressure switch on the Master. Switch it not bad, so there has to some pressure building up inside. Can't figure out why unless I put one of the cups on facing the wrong way. But the brakes work fine. I figure someone has made this mistake of knows what the problem is.
might help if you provide a clue about what car it is? and maybe a picture? the dual systems I'm familiar with have a separate part that has the pressure differential switch, which turns on the light. Some newer or foreign cars have fluid level switches on the master cylinder.
Do you not have enough pedal free play so there is some residual pressure ? Did you get something too close to the wiring and cause a fault?
It is on an ATV. But the design is just like our cars. Lots of free play. Peddle and rod are pulling back. But maybe I need to pull it apart and make sure nothing is sticking inside. Had not considered that.
If it has a pressure differential switch inside the master cylinder, then it's not like the cars I know about...
The Jalopy Journal
