Brake lights on all the time

Pull one wire off the switch. Lights go off?? Then it's NOT a "bad ground somewhere" or any other wiring issue.

There is an even chance that there is enough residual pressure built up to keep the sw activated. Most often the M/C pushrod doesn't have any freeplay. If the wheel cyl bleeder valves will turn, open one and see if the lights go off.

Speedy Jim

Jim,

The pedal is "really nice and firm....very little play" Which I like the feel of but must say that when I got it this way was about the same time I had problems with the light. So if this is the problem I need to adjust the length of the toggle screw on the MC push rod? or is it a problem with the MC itself? I'll try the wire trick ....good idea, I'm a bit embarrassed that I didn't think of that ;-)

Dan

Speedy Jim wrote:

Yes, adjust the "toggle screw". (Technically, the stop on the floor is supposed to be moved, but after half a century it probably ain't gonna!

Adjust it so that there is roughly 1/4" of freeplay at the top of the pedal before the pushrod hits the piston.

If there is *still* a problem afterward, then you can consider a problem inside the M/C. Jim

Thanks again Jim,

it was a problem with too much pressure although I'm uncertain about how it developed as the lights used to work fine, then the pressure seemed to increase. I wonder if I initially had an air bubble in the line that eventually worked its way out. I bled one wheel and the lights work normally now with a bit more play in the brake pedal. Now I either have air in that line or the pressure will most likely build up to where it is a problem again. I'll see what happens and then adjust the floor stop if it builds up again. Thanks again for your help. This issue has been bugging me for quite a while since I first assumed it was a bad switch.

Dan

Speedy Jim wrote:

Dan, Classic issue with the brakes, that will cause the symptom, is the broken down rubber inside the flex lines, closing off the inner portion of the tube. If that's happened, sometimes it can act like a valve and allow the pressure release that you have experienced, on the outflow side of the "valve" formed by the rubber inside the hose. Thus Replacing the flex hoses to each wheel might be the desired fix for your original problem.

I have experienced something very similar to your forst description. So similar , that it's the first thing that pops into my mind when I read the original symptoms. I watch to see if it gets cured otherwise, for there are many other items that can be cheaper to deal with.

Those flex lines are fairly inexpensive and well worth the money.

Remove "YOURPANTIES" to reply

MUADIB®

one small step for man,..... One giant leap for attorneys.

Hi again folks,

Thanks Muadib for the info. I think what is going on with my car is definately some sort of ball valving. Now a few days later I'm back to the breaks being on all the time. Well actually, sometimes when I get in the car in the AM they work fine but by the time I get to work they are constantly on again. The pressure must bleed a bit overnight.

Problem is this is a pretty fresh (complete) resto. Lines were all replaced about 5 years ago. The non-standard thing I did was to use Dot

5 fluid. Will this break down the rubbers worse than dot3? Is it possible that I have a piece of rust or something in the line from my fluid reservoire? I can't quite figure out why this should have happened.

Theoretically I should be able to bleed each wheel and there will be one wheel (with the bad line) that won't solve the pressure problem when I bleed it ....correct? Then perhaps I could just replace (or blow out) that line.

Are there other causes of this problem I'm not aware of?

Thanks for all your help.

Dan Miller Seattle

MUADIB® wrote:

Ok, the symptoms still point toward a hose in my opinion.

even with the new hoses back then it is very possible, and even likely if the hoses were not of the finest quality available...........newer stuff doesn't seem to last long...........I'd be bleeding from all brake lines and watching for variations in amount of fluid drawn at bleeding.................on wheel will realease the pressure, another will not. the flow problem will be obvious if you try the bad wheel first.

I am not at all familiar with the newer fluid. it is supposed to be compatible with the old parts, but not necessarily with the old fluid. If they got mixed and not flushed properly...............I don;t know what would happen. Anyone else???

Yes , it is possible, but the likelihood is seemingly less than the bad hose, this from the noted symptoms.

It may take bleeding each wheel one day at a time to figure it out, unless you can cause the pressure again shortly after releasing it by bleeding a wheel.

The line might be the problem, so I would recommend replacement if it is discovered that one is not releasing pressure on bleed screw opening.

Sure, there are other possibilities, but this one is very easy to identify and cure. Anything else I can think of will likely be an assembly issue or a clog as you mentioned before. Much more difficult to nail down.

Good luck

Remove "YOURPANTIES" to reply

MUADIB®

one small step for man,..... One giant leap for attorneys.

if the OP had a bad hose it would not keep the master cylinder pressurized(the hoses are "downstream" which is what is causing the lights to stay on...I think the pushrod is out of adjustment (too long...BTDT)

Good point..., ball valving in the hoses would only create abnormally high pressures downstream of the ball valve, Pressure might actually be low on the master cylinder side of the system.

I'm starting to think maybe it is a sticky master cylinder. I don't think the push rod is out of adjustment ...just by feel, and it doesn't explain the intermittent behavior I'm experiencing. I'll "adjust" it nonetheless. It really does sound like a ball valve problem, or a pressure buildup problem that then resolves over time (ball valving or not). Seems like it has to be right in the master cylinder though for it to keep that switch activated. I think I'm going to have to pull the master and see how it's working.

Another thought.... Is it possible my brake slaves are out of adjustment so that the return springs on the shoes are creating abnormally high back pressure from one of the wheels?

Dan Seattle WA USA

Joey Tribiani wrote:

Dan, not likely.....not impossible i guess, but not likely...having experienced the downside of a pushrod that is adjusted too tight on the brake pedal, i can say that your symptoms are identical..and what happens (as explained by speedy Jim, probably better than im gonna do) is the master cylinder does not return all the way and blocks small ports that should be uncovered..this allows pressure to "build up"....it can even make the brakes drag....it will bleed off in time...(*like overnight as you described)....next time they stay on, stop on a slight incline(very slight) and let off the brake...the car should roll and the brakes not drag....i'd be willing to bet that the car won't roll on a slight incline....the "freeplay" of the pedal can be deceiving because th emastercylinder's piston moves with little pressure required at first...so what you perceive as "freeplay" may be actual movement of the piston....if you adjust the pushrod shorter do it in very small increments because a little really is "alot"...you can go from holding pressure(make the pedal solid feeling and the brakes drag/lights stay on) to having to pump the brakes to build pressure, very easily...