Brake light
- Thread starter mustangdave
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I think there is a switch on the brake pedalmustangdave said:
Edit:
http://www.mustangsunlimited.com/keyword.asp?Keywords=brake+switch
69 Rustang
Member
The 64 1/2's had a hydraulic pressure switch that screwed into the master cylinder. Mustangs built after that have a mechanical switch that mounts on the brake pedal to activate the brake lights from an eccentric.
The wires going to the distribution block on disk brake cars (at least for the 69 and later cars that is) is a brake failure warning dash light that is to indicate braking problems.
The wires going to the distribution block on disk brake cars (at least for the 69 and later cars that is) is a brake failure warning dash light that is to indicate braking problems.
Rusty67
Dirt-Old 20+Year Member
69Rcode_Mach1
Active Member
It is a switch that has a cylinder on your brake pedal go through it, right next to the pushrod from the master cylinder, when you push it it compresses a small sensor with a spring on it to complete the circuit therefore turning on your brake lights.
Tim65GT
Active Member
Originally posted by Rusty67:
I was wondering the same thing.
If you are talking about the dash brake warning light, it is activated when you loose pressure front or rear, it causes a pintle inside to move. This does two things:
1. It stops fluid loss to whatever circuit it loosing fluid.
2. Completes the ground circuit for the warning light on the dash.
The switch is the white plastic item in the top middle.
View attachment 489279
According to the availability info at Mustangs Unlimited, this feature was on '67 and newer only.
I was wondering the same thing.
If you are talking about the dash brake warning light, it is activated when you loose pressure front or rear, it causes a pintle inside to move. This does two things:
1. It stops fluid loss to whatever circuit it loosing fluid.
2. Completes the ground circuit for the warning light on the dash.
The switch is the white plastic item in the top middle.
View attachment 489279
According to the availability info at Mustangs Unlimited, this feature was on '67 and newer only.
Rusty67
Dirt-Old 20+Year Member
While we are on this subject, my distrobution block went bad and I didn't replace it with another block. Instead I just put in a residual pressure valve to the rear and a t-block for my front discs. Is there a way to hook up a brake warning light like this one without using one of those distrobution blocks ? I have never seen one that was built for just 1 line.
Rusty67
Dirt-Old 20+Year Member
I got that part figured out. I'm just wondering if anyone makes a pressure sensor for a single line. I've never seen one.
Sorry I wasn't clearer. I was talking about the warning light on the dash.
So is the distribution block rebuildable; mine seems to be stuck. I have rebled the brakes numerous times trying to recenter whatever it is with no luck. I have seen plenty of replacement proportioning valves but never a stock distribution valve.
So is the distribution block rebuildable; mine seems to be stuck. I have rebled the brakes numerous times trying to recenter whatever it is with no luck. I have seen plenty of replacement proportioning valves but never a stock distribution valve.
krash kendall
Active Member
Sometimes if the hourglass shaped rod in the proportioning valve goes to a fully closed position on either the front or the back line, it will want to stay there. You have to remove the valve, dissassemble it to a point where you can physically help it back to center, then put it back on an rebleed the system.
EDIT: If there isn't a warning light sending unit, then the shaft may not be hourglass shaped.
EDIT: If there isn't a warning light sending unit, then the shaft may not be hourglass shaped.
mustangdave said:
It’s possibly stuck but not probably. Some can be hard to recenter. Which one aren’t working, front or back? Let’s say its the back ones that had the leak. The proportioning block has slid over and stopped fluid going to the back. How to correct this is to...
1. Fix the leak in the back brakes.
2. Make sure the back bleeders are closed.
3. Fill the master cylinder.
4. Open and leave open the bleeders in the front.
5. Climb into the car; turn the ignition on so the dash brake light is on.
6. Push the brake pedal moderately until the light turns off, but you don’t want to go to far and slide it all the way over and cut off the front brakes.
7. Close front bleeders.
8. Fill M/C w/ brake fluid.
9. Open the brake bleeders in back first. Leave open until fluid comes out on its own.
10. Fill M/C again
11. Open front bleeders until fluid comes out on its own.
12. Do the normal bleed procedures have someone pump brakes and hold while you crack the bleeder until the pedal goes to the floor. Repeat on other 3 wheels.
Just a little FYI... I never thought gravity bleeding brakes did anything, but working as a mechanic in a general automotive repair shop has made me a believer. It GREATLY reduces the amount of time 2 people are screaming pump "them" and "holding". Sorry for the long detail post but easiest way for me to make sure I was clear.
Graham
krash kendall
Active Member
Yeah, last time I had to recenter one I was able to get a small screwdriver down that hole and help it along back to center. You will have to loosen the brake lines so when you are pushing the shaft it will release the pressure in one direction and suction from the other. Some types have a bleeder at the front which is handy if you are lucky enough to have to push it in that direction.
krash kendall
Active Member
The problem that get them stuck is when they are fully closed in one direction. If they are only partially closed they will recenter as blk02 stated because the fluid will have a path to start to build pressure in the line, pushing the shaft back to center. However if you have been driving with a major breach in the line the shaft will fully bypass the port, closing any path to those lines, requiring a manual recenter. The valve isn't exactly "stuck", it is actually doing it's job.
Great tips guys. Blk 02, there are NO leaks. This happened when I installed new rear brake lines and tried to bleed them. I'm using speed bleeders so I was working alone. After doing the back, I did the frt. just to make sure I had clean fluid everywhere. I think you guys have explained how it works though so I can get it right. I decided while doing my frt. end rebuild to slap some discs on the frt. but I'm sure I'll have the same problem; at least now I have aclue as to how to fix it.
Rusty67
Dirt-Old 20+Year Member
krash kendall said:
Ever had one that you can't unstick ? I've got one right now. Any tips on how to unstick it are welcome.
dave, you really need a second person to center the switch. since you replaced the rear lines, you need to create a "leak" in the front line to recenter the switch. have someone pump up the pedal, then you crack a bleeder valve in the front until the light goes out. if you are not fast enough, then you need to a crack a rear valve open.
that said, there is a faster way. if you remove the switch, you can replace it with a bolt that has the end rounded off, and use that to help center the switch. dont force it though as you risk bending the plunger. and when doing future brake jobs, you can use the same bolt to keep the plunger centered while you bleed the system. then just replace the switch.
that said, there is a faster way. if you remove the switch, you can replace it with a bolt that has the end rounded off, and use that to help center the switch. dont force it though as you risk bending the plunger. and when doing future brake jobs, you can use the same bolt to keep the plunger centered while you bleed the system. then just replace the switch.
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