letitsnow Posted August 8, 2012 Share Posted August 8, 2012 I believe I'm having issues with the brake warning switch. It comes on under heavy braking, and I believe I can feel the switch in the pedal. Whenever the light comes on I can feel a notch or pop in the pedal and again when it goes out. If the light comes on, hitting the pedal again can cause it to go out. It only comes on under heavy braking. I've bled the brakes starting from the right rear going to left front. I've adjusted the rear brakes. Can the switch cause lower pressure on one of the circuits? I feel like the rear brakes aren't effective enough, but this may be because I have parts store shoes and porterfield front pads. Autocrossing, the fronts seem to lock up fairly easy. Quote Link to comment Share on other sites More sharing options...
RebekahsZ Posted August 8, 2012 Share Posted August 8, 2012 I think you can take the mechanism out of the pressure differential switch. I just eliminated it. Quote Link to comment Share on other sites More sharing options...
letitsnow Posted August 8, 2012 Author Share Posted August 8, 2012 Taking the mechanism out would link the front and rear circuits if I'm looking at the diagram in the FSM correctly. I might just take it out like you did. Quote Link to comment Share on other sites More sharing options...
RebekahsZ Posted August 8, 2012 Share Posted August 8, 2012 😳oops. I guess you are right. Wouldn't want that! Quote Link to comment Share on other sites More sharing options...
h4nsm0l3m4n Posted August 8, 2012 Share Posted August 8, 2012 (edited) The brake warning switch turns on when one of the two brake circuits pressure is a lot lower than the other one (ie failed). I believe the mechanism inside will close off the lower pressured circuit so you do not loose full system pressure and retain some brake usage.. I had this happen to me when I did my rear disc upgrade. A lot of fluid had drained out of my rear brake lines. However, I could not get sufficient new fluid back in because the switch would close off the rear circuit when I would pump the pedal. What I ended up doing is first thoroughly bleeding the master cylinder. Then opened up all the calipers and let the system gravity bleed itself for a good while. This got sufficient fluid past the switch that both circuits would pressurize evenly enough not to trip the switch when I would pump the pedal. I could then proceed to bleed the brakes normally. Edited August 8, 2012 by h4nsm0l3m4n Quote Link to comment Share on other sites More sharing options...
letitsnow Posted August 8, 2012 Author Share Posted August 8, 2012 (edited) I can bleed the system normally though, it's only under hard braking that it does anything, moderate pressure braking seems normal. Left front also seems to lock up before any other wheel, if that means anything to anybody. Stock everything(good shape) except pads, I forgot to mention it before. I guess I'll try bleeding the master again, can't hurt. here's a pic of the switch from the FSM, just for reference. Edited August 8, 2012 by letitsnow Quote Link to comment Share on other sites More sharing options...
beermanpete Posted August 8, 2012 Share Posted August 8, 2012 I suspect what you feel is the master cylinder piston for the side with low pressure bottoming out when the pressure drops too much. The warning light switch is not part of the master and I doubt you would be able to feel its operation in the brake pedal. Perhaps the master cylinder is leaking internally. Does the the pedal sink if you hold steady pressure on it for a while? Quote Link to comment Share on other sites More sharing options...
letitsnow Posted August 10, 2012 Author Share Posted August 10, 2012 Pedal does not seem to sink while holding it. The light doesn't come on until I let off the pedal, one side is holding pressure longer than the other? Quote Link to comment Share on other sites More sharing options...
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