1939 ford brake lights stuck on
 

Here s what is going on Lost brakes had a bad hose third hose (one for back lines) Replaced it Also replaced master cyl. Brake lights stuck on So got new switch installed works fine, Then when car sits for a hr no pedal Checked system no leaks all good Took out new cyl replaced old one now got brakes but stop switch not working (new one that worked with other cyl) Brake lights stuck on Crack loose at master and goes out till brakes are applied What am I missing Any Ideas? (New cyl. looks to be leaking in front so I am calling that one junk out of box)

Re: 1939 ford brake lights stuck on
 

I'm not sure I'm following this. Why did you replace the master cylinder in the first place? You have a new pressure switch, did something happen to it? Is the new switch broken? Why not get another one? There are several upgrades you could do. Get a new low pressure switch or replace the pressure switch with a mechanical switch.

Re: 1939 ford brake lights stuck on
 

When I lost brakes I just decided that's what is was. Old one was in. Car for years so I replaced it when I did hose. My switch was working with new cyl Just put it back together this afternoon

Re: 1939 ford brake lights stuck on
 

I didn't read anything about you bleeding the sys after the new hose. The new cyl might have a different plunger, and the rod needs adjusted, no petal after an hour sounds like air in the system.

Re: 1939 ford brake lights stuck on
 

Check the condition of the wiring is another possibility. I had one with bad insulation with the lights stuck on. Both wires had a bare spot and were touching. Could have disturbed it when you swapped the master cylinder

Re: 1939 ford brake lights stuck on
 

Yes I bled system Matter of fact since I started with this Its been bled a bunch of times and no air at all just fluid

Re: 1939 ford brake lights stuck on
 

First thing I checked all wiring looks good

Re: 1939 ford brake lights stuck on
 

So, could you explain to me what the problems are currently? You are using the original master cylinder and both the new pressure switch and the old pressure switch are sticking on?

Re: 1939 ford brake lights stuck on
 

When I took out new cyl today its leaking in front around plunger Must been getting air and loosing pres. So that cyl is out

Re: 1939 ford brake lights stuck on
 

Ok using old master cyl Only have one new press switch same one that Was working with new cyl that is junk Now not working with old master Everything two weeks old Maybe I got to get a new switch Can I check mine with a meter or test light?

Re: 1939 ford brake lights stuck on
 

When I took out new cyl today its leaking in front around plunger Must been getting air and loosing pres. So that cyl is out

Re: 1939 ford brake lights stuck on
 

i had a similar prob once, but my brakes were builidng and maintaining pressure. i had new master then a new master rebuild kit. after i drove it a while, i'd notice the brakes dragging and the light on. a mechanic said i had the wrong relief valve in the master. he fixed it. others have told me that it prob wasn't the wrong relief valve, but the problem went away.

Re: 1939 ford brake lights stuck on
 

Is the new pressure switch stuck on or not working? It would be odd that two pressure switches would both stick on, are you sure the pressure is releasing in the system?

Re: 1939 ford brake lights stuck on
 

I drove car and brakes working fine if you release pres lights go out Step on pedal and lights stay on

Re: 1939 ford brake lights stuck on
 

What does "if you release pres lights go out" mean? Like in opening a bleed screw?
Then if you step on the pedal again the lights come on and stay on? That sounds like pressure is remaining in the line activating the switch.

Re: 1939 ford brake lights stuck on
 

Yep thats whats going on

Re: 1939 ford brake lights stuck on
 

Maybe my old master is no working 100 percent

Re: 1939 ford brake lights stuck on
 

Well guys thank you for all the help Going back to garage and mess with it for a while Maybe something will come to me Again Thanks

Re: 1939 ford brake lights stuck on
 

Sounds like it is holding pressure for sure.

Re: 1939 ford brake lights stuck on
 

Sounds like I need to get a new cyl (old one is not working right) I think that will be my next move

Re: 1939 ford brake lights stuck on
 

Is the rod from the brake pedal to the m/cyl too long??
Paul in CT

Re: 1939 ford brake lights stuck on
 

1931 flamingo has my idea also.

Re: 1939 ford brake lights stuck on
 

Same rod and adjustment same master cyl . Going to jack it up tomorrow and check that. It's got me stumped. It's been working last 10 years

Re: 1939 ford brake lights stuck on
 

Well Checked rod Rod Ok (also adj rod loose) I would say its the master cyl Now after it sets a while Lights will go off All brakes and every other thing works correct Master cyl Sticking on press release for switch Thanks for all help Now I know whats going on

Re: 1939 ford brake lights stuck on
 

I wish I could tell what you did when is rod loose now was it tight before was it keeping master Cylinder from returning was switch still pressurized i wish we could understand exactly what you started with and what you did one slow step at a time what is Master cyl Sticking on press release for switch mean can you write in full sentences with some punctuation so WE can make SOME sense of what you are actually doing making my head hurt?

Re: 1939 ford brake lights stuck on
 

Are you using DOT 5 silicone fluid?
It has been known to affect pressure switches.
Bruce

Re: 1939 ford brake lights stuck on
 

Bruce I am using DOT 3 Brake Fluid. That s all they sell at auto parts store by me. When I checked brake rod it was just touching, So I backed it off a little ,So now it is loose. Now if you drive car and park it ,brake lights stick on for a while(like ten minutes or so) So I am thinking Press release in Master Cyl. is sticking or something. So for now I sent back New master cyl. that I got for exchange one. The new one was new not rebuilt, But would not hold pres. I did notice at front plunger that one was leaking a little. It was wet with brake fluid when I removed it. Since I put old master cyl. back on I have good brakes, no leaks, But like I said brake lights stick on for a while now. Just going to wait till I get the exchange one and start over again Its been a pain in the Butt .

Re: 1939 ford brake lights stuck on
 

Make sure the pedal is adjusted so that the plunger in the MC comes back far enough for the fluid to return to the MC reservoir. You can look down in the fill hole and you should see the bleed back hole down on the plunger.
IF this adjustment is not right it could cause pressure to remain in the system.

Re: 1939 ford brake lights stuck on
 

The cap on most master cylinders have a small hole for it to vent, Could the vent be plugged up? It does need to vent or it will hold a certain amount of pressure.

Re: 1939 ford brake lights stuck on
 

I drove it around a little today. Lights are sticking on for a couple minutes now. It's getting better. But do not know the problem. At least I can still use it.

Re: 1939 ford brake lights stuck on
 

Your problem is your brake rod that goes from the pedal and into the master cylinder...shorten it a few turns and this will release the holding pressure...

Re: 1939 ford brake lights stuck on
 

I had a similar problem with mine.Everything worked fine when car was cool. After short drives, I had the brakes getting hot dragging and the brake lights sticking on and coming on after car was parked. The heat under the hood would make mine come on. I checked this by heating the master cylinder with a heat gun. Turns out the bleed hole in front of the main inlet was stopped up on mine. When I rebuilt the MC I over looked the hole it is so small. I found a bit the right size and drilled the crud out and all has been well since.

Re: 1939 ford brake lights stuck on
 

This happened all the time with me until I wrapped the brakelines closest to the exhaust pipes with a small insulating fiberglass sock.

Re: 1939 ford brake lights stuck on
 

Those are two good things that I will check out for sure