brake lights not staying on..

[35fordcoupe]

If I press the brakes the lights flash on then go off. If I pump the brake pedal to build pressure they will come on and stay on consistantly. I have a hydraulic switch and while the brakes work ok I am going to bleed them again when I get the chance. Will air in the system cause issues for this hydraulic brake switch? What else may be the issue? Thanks

[Hot Rod Surfer]

My 2c says bleed it!

[34_40]

What type of switch?? If it's a hydraulic switch in the brake line, they're known to have a problem like this one. I think the diaphragm is failing. Most guys have now gone to the mechanical switch for this reason. Others don't think the hydraulic switch causes any concerns... Like Surfer suggested, try bleeding the system first. If it doesn't fix the problem, replace the hydraulic switch with a new one and re-bleed.

If you've already got a mechanical switch, have someone step on the pedal while you watch it's operation and see if there is something binding or in mis-alignment.. A test light or meter will tell you when the connection is being made and may help in diagnoses..

[cffisher]

You didn't say what type brakes you have. How ever, no pressure means the place where you have the switch has no pressure until you pump it up. So, is the pedal low at first, and when you pump them, it gets higher ? If so, that means brake adjustment is not correct. If it was air, it would be higher, but, spongy.

My guess is bleed them. You can compress air, you can not compress fluid

[dlotraf33]

If the brake switch is easily accessable you may want to bleed the switch itself. I had one that did that, and after several blead still wouldn't function correctly. I blead the switch, just loosened the switch like a blead screw, and that cured the problem. I guess a small pocket of air was traped there and normal bleading wouldn't get it out. The pedal was good not spungy, but brake like wouldn't stay on. Now I use mechanical switches............ Hope this helps...........

[rspears]

If I press the brakes the lights flash on then go off. If I pump the brake pedal to build pressure they will come on and stay on consistantly. I have a hydraulic switch and while the brakes work ok I am going to bleed them again when I get the chance. Will air in the system cause issues for this hydraulic brake switch? What else may be the issue? Thanks

Can you give us an overview of your system? Four wheel drums? Discs front, drums rear? Discs all around? Master above wheel cylinders (firewall mount) or below (under floor mount)? Residual valves? Some of the answers given seem to be assuming a system configuration (like brakes being out of adjustment?), which may or may not be applicable based on your system.

[35fordcoupe]

Sorry, I posted then went out to work on the car, but scattered showers prevented me from looking closer at this. I have discs front and rear (GM metric discs in front with '97 Camaro discs in rear). The MC is under the floor with a residual valve in each line as well as a proportioning valve in the rear line.

Louey - the pedal isn't really low, but pumping does seem to build some pressure.

I'll probably start by bleeding and also try and do a better job bleeding the master cylinder since I don't have good equipment to do that. I will try bleeding the switch too and hopefully that will fix it, but I won't be back on it for a couple weeks. Next time I'll probably get a mechanical switch. The guy at Speedway reminded me I need the switch when I was ordering all my brake parts and thinking back a mechanical switch seems more reliable. Thanks guys.

[rspears]

There have been confirmed cases of some early through the frame fittings creating air traps that cannot be bled out. If you have those fittings you might keep that in mind if normal bleeding does not get rid of your spongy pedal.

[35fordcoupe]

nope I just have a coupe tabs welded on. I don't necessarily have a problem bleeding it's more that I wasn't thorough enough and until I can get around to doing a better job of it I was wondering the chances that air could cause the problem.