pin on brakes prop valve assembly on the 84

[R72K5]

ok the prop/combo valve for the brakes on the 84 has the pin to push with rubber boot over it, on the end of the valve assembly, the brake light is still on after bleeding it, i know it is supposed ot be pushed like during bleeding or something

someone has to know something about this

what are you supposed to do ?
the rear frame rail 1/4" hard line blew out and so we have to replace entire rear line from front to back, so it will be a major bleeding process,
no wonder we werent getting fluid to the wheel cylinders back there, lol.



thanks

 

[dyeager535]

Not much help, but here's a post where it's at least talked about.

I've personally never had to mess with it.

 

[dcubb]

In your case, to clear the brake malfunction light, have someone pump the pedal several times and then hold it down firmly. Open the bleeder on either one of the front calipers to release the pressure quickly. This will usually re-center the piston in the combination valve, turning off the light. Just be sure that all the air is out of the rear portion of the brake system first. The pin on the end of the valve is to over-ride the hold-off function of the valve that pertains to the FRONT brakes only. If you're bleeding the system the old fashioned way, (One person pumping the pedal, another bleeding), don't mess with the pin. You'll only need to activate it if you're gravity bleeding or using a pressure bleeder. Again, the end of the combo valve that has the pin is for the front part of the brake system. Hope this helps.

 

[R72K5]

we been bleeding front system also

the front work so well that the tires screech to halt

rear line was rusted out it blew up so new one is on now and now finally have fluid to rear but very little pressure

also the old master cylinder had orange crud come out of thew rear line port, it was clogged and wouldnt put any fluid out, and same with the line form there ot the combo valve, it was bad we blasted it out with comepressor and also the combo valve rear circuit

and then the entire frame rail line to rear, a bunch of crud came out of that too after putting new section of line on

cant get the rears ot bleed right,t jut not good pressure at all, but have good fluid and no air now

the m/c rear port puts out good pressure

somewhere its being blocked
i am wondering about the combo valve maybe its stuck all way over for fronts only
i beat on it with hammer but it helped none

the pin comes out when have pedal down then retracts when you let off pedal


thanks

 

[dcubb]

How were the brakes before the line blew? from the description of the crap coming out of the m/c and lines it's a good possibility that the combo valve is faulty. however, the malfunction light switch shuttle valve and rear brake pressure valve are two separate entities within the combo valve. If the brakes were working okay before the line failure I would suspect that there is still air in the rear circuit. Due to the volume of the 1/4" line all the way to the back of the vehicle, it can be a bitch to get a air bubble all the way out. When I did the rear disc conversion on my Blazer, I couldn't get all the air bled completely by the conventional method (buddy pumping the pedal, me opening bleeders, went through 2 quarts of fluid with still no success). Finally said screw it and bought a pressure bleeder. Worked great the first time around. Great big ole air bubble popped right out. Anyway, just because there is good flow of fluid at the bleeder doesn't mean that there's not an air bubble trapped somewhere in the line just moving back and forth every time the pedal is pumped.