proportioning valve switch (brake light)

[hetrickw]

recently bled front/back brakes. immediately noticed brake dummy light staying on for a few minutes. can anyone tell me about the purple wires/switch going into the proportioning valve? It's leaking slightly and hadn't done so previously. what constitutes a brake light illumination/failure..... have disc and drum.

thanks bill

 

[gpierce]

The light goes on when those two wires have continuity between them. The light would get tripped (connecting the wires together inside the switch) when the valve inside the valve goes all the way to the front or back brakes indicating loss of pressure on one of the two systems.

 

[marks73]

Sounds as though you still have a leak somewhere.

 

[hetrickw]

thanks all

 

[marks73]

Did you pull the drums before you bled the rears?

 

[hetrickw]

Did you pull the drums before you bled the rears?

Mark,

No, I just bled starting from back passenger side to back drivers then moved forward. I seemed to have got all the air out but, I'm going to try again this weekend. It's probably just air in the line since I pulled the master cylinder to clean and paint.

 

[hetrickw]

Anyone got an answer why I cant get the brakes to function properly. I've put a couple quarts through the all for lines (several occasions) with no bubbles coming through and still have a momentary brake light illumination and soft brakes until I pump them a few times. I checked the vacuum to the booster and it appears good. This started after I pullied the master cylinder to paint it a few weeks back. Before then it was working fine. Marks73, I've never heard of pulling the drums to bleed the brakes. NO fluid loss anywhere in the system. thanks for any advice.

Bill

 

[72HCODE]

the plunger inside the Prop valve that triggers the sensor might be stuck off center. or the internal pressure sensor plunger could be leaking forcing the sensor to trigger off.

What can happen is the sensor had sat happy in the center for 40 years, you pull the master drain the fluid for a brake repair. then refill and either a piece of dirt has jammed the plunger or a seal went, or could even be an air bubble inside the prop valve causing the plunger to sit off center.

you could try a vacuum brake bleeder, but you may have to pull the prop valve out, or attempt to open the bottom nut on the unit to release the plunger and spring mechanics and rebuild the prop valve.

it could quickly turn into a nightmare with original 40 year old brake lines.

today you can get a replacement prop valve or a rebuild kit. 8 years ago neither was available. I had to cobble together 3 junk yard prop valves into one working unit.

i also had to replace ALL the brake lines on my car as they snapped off when trying to remove the prop valve.

 

[jbojo]

the plunger inside the Prop valve that triggers the sensor might be stuck off center. or the internal pressure sensor plunger could be leaking forcing the sensor to trigger off.

What can happen is the sensor had sat happy in the center for 40 years, you pull the master drain the fluid for a brake repair. then refill and either a piece of dirt has jammed the plunger or a seal went, or could even be an air bubble inside the prop valve causing the plunger to sit off center.

you could try a vacuum brake bleeder, but you may have to pull the prop valve out, or attempt to open the bottom nut on the unit to release the plunger and spring mechanics and rebuild the prop valve.

it could quickly turn into a nightmare with original 40 year old brake lines.

today you can get a replacement prop valve or a rebuild kit. 8 years ago neither was available. I had to cobble together 3 junk yard prop valves into one working unit.

i also had to replace ALL the brake lines on my car as they snapped off when trying to remove the prop valve.

I had a similar issue with a supposedly rebuilt valve that I purchased. When I took it apart I found that the o ring was installed improperly and crushed. It is an easy fix, just take off the bottom nut and clean the internals completely. The shaft should move freely. If I remember right there is only 2 peices in there. I believe I have the old one and can take pics if you need to see what its like.

Like 72HCODE mentioned the hard part is going to be getting the brake lines disconected. I broke a couple of them too.

 

[hetrickw]

That's what I was leaning towards. I'll do just that. Thanks for the great advice. I really appreciate all the corporate knowledge here!

Bill

 

[matrixx]

I'm currently undergoing this job to my coupe. All winter long I have gone outside and sprayed the bolts with pb blaster and let them sit a week and then do it again. I guess it payed off because 2 days ago I put my line wrench on the brake lines and they just started to turn. I even soaked that prop valve as well and i proceeded to crack those just to see if they would loosen freely. Now granted I have not unscrewed them all the way out yet but I am confident that everything will be ok. I just hope the lines dont twist as im unscrewing the nut.

 

[wwhite72]

Booster diaphram failure? Happened to mine, no leaks no real brakes either. As for the valve. All i can say is SSBC valve block and be done with it.

 

[hetrickw]

I was thinking that also but after a day or so of working on it I have the brakes back in full function again. I appreciate it 72HCODe & jbojo....... you pointed me in the right direction.......

bill