We have a '51 Ford Custom, all stock. When we got the car it had sat a long time and we did the normal replacements; water pumps, hoses, belts, plugs, wires, wheel cylinders, master cylinder, one hunk of brake line, etc. When we got it together, the brake lights didnt work. The switch was nasty inside so we ordered a new switch. Replaced the switch and it worked fine for about 10 minutes, then the brake lights stayed stuck on. If you unhook either of the wires from the switch, the lights go off. I pulled the switch out, made sure it was clean inside, and put it back. It worked for about 10 minutes again then the lights stayed stuck on. Since those switches are cheap, I bought a new switch hoping we just had a bad one. The new switch does the same exact thing. It worked fine for 10-15 minutes, I walked away and when I came back 15 minutes later the lights were stuck on. What could be creating pressure as the car sits to cause the switch to trip making the lights come on? When the lights are stuck on, nothing changes if you pump the brakes. But if you break the switch loose releasing the pressure on it, then they go out. I am at a loss but dont really trust taking it to any local shop since none of them deal with anything this old any more. Any help will be greatly appreciated.
I'd first look at the rod that pushes on the master piston. If it is set so the piston cannot return, it could be the issue. you need a tiny bit of free play before the rod contacts the piston. grab the rod and see if it wiggles a bit, side to side, up or down. It's best to check there, rather than just feeling the pedal, because the freeplay there could be some bushing wear.
yeabut... a swelled up flex line would make that wheel drag due to trapped pressure, but his switch is on the other side of that situation. I believe the switch is right at the master outlet? .
Thanks guys. I just crawled under the car and there is no play in anything on the master cylinder/pedal ***embly. When I pushed up on the peddle from under the car, the lights went out.
I soaked everything down with WD40, worked the pedal a few times, and there is a little play in the rod now. So far the lights have not come back on.
It's not fixed, but at least I am now on the right track thanks to this forum. I took the car for a short ride, happy I had the coolant leak fixed, turn signals working, and working brake lights. I got home, parked the car and walked around the back of it right away to check the brake lights; they were off. I wandered away for about 10 minutes, came back, and they were on. I reached inside the car and pulled up on the brake pedal (it must have moved an inch or inch and a half), and the lights went out. I need to figure out what is causing the pedal to not return to "home". Maybe it needs a new/another return spring, or it felt like the rubber boot under the car was really dragging on the pedal, that might need replaced.
Could be any of those, but when you used WD40 earlier...that stuff is not really good for long lasting lube on pedal bushings. Oil is better, after you got it looser with the WD.
I would pull off everything attached to the pedal and clean it up good, paint it too. There is a rubber boot at the back of the master. It may be totally dried out. Do you have the manual for the car?
No, we dont have the manual for the car. When we replaced the master cylinder, I am pretty sure it came with a new boot as it was in really good shape when I crawled under there today. However I did notice the boot on the bottom of the pedal under the car (that seals out the road gunk) was pretty dried out, and that was a couple of years ago so I am sure it hasnt gotten any better.
In the absence of any bind in the linkage or rust / crud causing drag on it, if the pedal return spring is doing its job properly (and is of the right length, strength and mounted properly so as to return the pedal) you shouldn't be able to pull the pedal up and find any movement. If you can then that's probably your free play being taken up / lost so the master cylinder isn't actually seeing any free play and causing what you're describing. You could adjust some more into it. There has to be a slight amount of free play on the pedal going down before it engages with the master - best done by feel. That free play has to be in the direct line of force of the pedal - slopping from side to side isn't free play and may leave pressure on the master. Chris
You really have to dig into it, look at all the bushings, return spring and for something binding the pedal. Disconnect it from the master and work it up and down. I like to lube all the pivot points with a good quality white grease. Page 7 of the Joblot catalog shows everything at the pedal. I know they are in the process of closing up for good, but give them a call if you see anything that may help you. http://www.joblotauto.com/
What Happydaze says is Correct in every way you have to have Rod Play otherwise you will have the Problem that is Happening Just my 3.5 cents or when the Cows Come Home!
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