Bleeding brakes again!

[papastoyss]

I am trying to bleed out the brake system on a friend's project, it has the Corvette style master w/the GM appearing proportiong (sp) valve. I am getting ok pressure from the front system & nada from the rear. I've tried manual bleeding w/a friend pumping the pedal & using my Mityvac both on the rear. Seems I recall discussion here a few yrs back about a plunger sticking in the prop. valve not allowing  fluid to flow to the rear. Am I all wet or is my buddy SOL?

[enjenjo]

http://www.ebay.com/itm/222583814772

Take out the brake warning switch on top of the valve. Install the tool into the hole. You may have to use a pick to center the valve first. Then bleed the brakes.

http://www.stevesnovasite.com/forums/showthread.php?t=137446  

This one tells you how to reset the valve.

[wayne petty]

I am trying to bleed out the brake system on a friend's project, it has the Corvette style master w/the GM appearing proportiong (sp) valve. I am getting ok pressure from the front system & nada from the rear. I've tried manual bleeding w/a friend pumping the pedal & using my Mityvac both on the rear. Seems I recall discussion here a few yrs back about a plunger sticking in the prop. valve not allowing  fluid to flow to the rear. Am I all wet or is my buddy SOL?

what the inside of most GM style prop valves look like..

http://i.imgur.com/ZIkteBr.jpg   click to view its too big for this forum


i would love for you to start your bleeding at the prop valve fittings.. the tubes that go into the top of the prop valve.. since only your rear brakes are failing to bleed.. you really only have one to loosen up.

i would love for you to NOT full stroke the pedal when doing this..   with the palm of your hand.. even i can't do this with my leg.. i can do it with my cane..  

Rapid Short pumps of the brake pedal .. usually not more than an inch from the top..  what you are trying to do is build pressure in the master.. but NOT push the seals past the fill ports in the side of the master.. this builds pressure and pushes fluid thru the system.. you will have to judge how fast and how far to push.. you won't feel it build any pressure we are talking 2 or 3 pounds maybe 10 pounds in a system that can create over 1000 pounds..

you can if there is a rubber cone in the rear system that when the pin moves toward the rear because of a lack of pressure to the rears can shut off all the flow to the rears.. getting fluid to the both front and rear lines from the master is a big trick to help..

i personally have had horrible issues with aftermarket prop valves where the inverted flare fittings just won't seal.. i have had to use the copper inverted flare copper seals used in A/C systems to get them to seal tightly..

please have gallons of water nearby when working with the brake lines on the master and prop valve.. brake fluid washes off instantly with water..  if you are quick enough with a wash down it won't damage the paint.    i have taken to painting the master and power brake boosters when not plated and just bare iron or steel.. with disc brake caliper paint..