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I replaced the almost unreachable brake light switch with a pressure switch on my '51 Chevy. The switch is on the passanger side frame rail and I replaced a connector with a "T". Brakes bled out and it worked fine. Then started sticking on, so I replaced the switch figuring it was bad, but it's sticking on again. The hydraulic brake system is otherwise stock, with a rebuilt original single pot M/C..
what can be wrong?
There is a possibility that the master has residual valve(s) in it and holding pressure in the lines..
That crossed my mind. I checked the '49-'53 shop manual but there is no mention ither way... I did however just notice that the brake pedal was quite stiff. I cracked a bleeder and it had a little pressure on it. Re-bled it all out and it's back to normal.. Old fluid possibly? or was that DOT-3 synthetic a bad idea? The DOT-3 syn was a fresh bottle I had on the shelf when I redid the front brakes. Said compatible with all DOT-3 and DOT-4 systems, so I figured it was ok.. I'v pumped a crap load of fluid thru it now. master has been filled 3 or 4 times out of that DOT-3 syn bottle
What psi is required to close the switch and turn on the brake lights??? Could be a low pressure switch, like you'd use for an oil pressure light, and the residual pressure as mentioned by 34_40 is closing the switch.......
PS--Please don't ask how I learned this!!!!!!!!!!!!!!!!!!!!!!:o:o:LOL:
My 57 Chevy dump truck has the pedal throgh the floor with m/c under floor. The brake lights were staying on and killing the battery ..After a lot of changng this and that. I found that the return spring in the pedal was the problem. seems the weight of the pedal after a time was enough to turn on the switch... New spring no lights on when not wanted.
How about your MC pushrod length? If it's adjustable it needs a bit of free play when off the brake, to allow the MC to return all the way and relieve pressure, right?
It takes a touch of pressure to turn it on. I tested it that way to see how sensitive it was. The switch is 'correct' for a 1965 Rambler American, which I know from having owned 1, the switch is right under the master cylinder in it's own port.. However, the switch is a stock item at my local carquest so it may double as an oil light sender.Quote:
Originally Posted by Dave Severson
I'll have to see if it's weak or distressed, but it does come back up pretty easyQuote:
Originally Posted by cffisher
I'll have to check that and slacken it up a little if it is.Quote:
Originally Posted by rspears
I had this happen on a 53 plym. years ago it turned out the vent hole in the cap was pluged up try washing the m/c cap......ted
The cap is a 3/4" plug that takes a 1" wrench to remove/ install.. However it won't tighten down. It spins out and while it won't come out, it's loose. Looking at the cap, I noticed the area near the hex face is recessed with no threads. I fixed the issue with a copper washer. Could that have caused it? if there's a vacuum on it because it's sealed so tight? I think there is supposed to be some type of washer but possibly somthing breathable. I bought an extra washer so what I think I'll do is knock a few notch lines in the washer with a chisel so that air can escape and ride it around/ see if that fixes it.
Yep, tha's probably it.. the cover needs to breathe.