Dnix Posted November 13, 2023 Author Share Posted November 13, 2023 I just replaced the bad line. When I stand on the pedal should I have the rear pass bleeder open? Thanks for the info Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted November 13, 2023 Share Posted November 13, 2023 Large file sizes on the forum will cause the picture not to load. You can use the resize/big size button in the right hand column to do it automatically. Link to comment Share on other sites More sharing options...
Gary Lewis Posted November 13, 2023 Share Posted November 13, 2023 Gary, Respectfully I'm referring to the multifunction valve found in our generation trucks, NOT the pressure differential valve used on 1967-'72 trucks pictured here. (From our good friend Keith Dickson at the Fordifction forum) Hopefully he will not object to my cribbing some of his writeup if credit is given. To which he says: This diagram from the Ford Truck Shop Manual isn't 100% accurate, as the factory piece actually used has 5 ports (plus the switch port) as opposed to the 4-port Mustang version showed here. However, the principle is the same. Unlike a metering valve or a proportioning valve, a pressure differential valve doesn't have any preset pressure settings to delay or to reduce the hydraulic pressure being applied. It's just a spool suspended and balanced inside the valve body between equal pressures of the front and rear brake circuits. If the pressure in either circuit is unequal, the spool is pushed to the low pressure side, closing the switch contacts and illuminating the dash-mounted warning light...simple. It doesn't have any metering function for the front brake circuit and no proportioning function to the rear brake circuit like the all-in-one brake assemblies" Way farther down the page. https://www.fordification.com/tech/propvalve101.htm is the correct diagram for our generation trucks. " This is the combination valve as used on '73-later trucks equipped with front disc and rear drum brakes for trucks under 6,800# GVW." Note, on the left, the metering valve bleeder. Jim - Thanks for that. Link to comment Share on other sites More sharing options...
Dnix Posted November 13, 2023 Author Share Posted November 13, 2023 Jim - Thanks for that. I meant sorry for resetting the proportion Valve. I realized that it would need to be closed. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted November 13, 2023 Share Posted November 13, 2023 I meant sorry for resetting the proportion Valve. I realized that it would need to be closed. It seems you have a wet fitting. Is there a leak, or did you crack the line nut loose to check for fluid? Also looks like the spring loaded plunger from the brake warning switch has popped out. . Getting the shuttle to move was a challenge 40 years ago when Ford suggested to stand on the pedal. Crud, corrosion and rock hard O-rings may make it impossible today. (or, maybe not. I can't speak to the condition of your brake system) If you have a vacuum bleeder like my Mity-Vac you could fill the cup with fresh fluid and reverse the ports on the pistol to pump fluid from the bleeder towards the master cylinder. That was the only way I used to be able to get the hydraulic clutch on my GSXR 1100 bled. Link to comment Share on other sites More sharing options...
Dnix Posted November 13, 2023 Author Share Posted November 13, 2023 It seems you have a wet fitting. Is there a leak, or did you crack the line nut loose to check for fluid? Also looks like the spring loaded plunger from the brake warning switch has popped out. . Getting the shuttle to move was a challenge 40 years ago when Ford suggested to stand on the pedal. Crud, corrosion and rock hard O-rings may make it impossible today. (or, maybe not. I can't speak to the condition of your brake system) If you have a vacuum bleeder like my Mity-Vac you could fill the cup with fresh fluid and reverse the ports on the pistol to pump fluid from the bleeder towards the master cylinder. That was the only way I used to be able to get the hydraulic clutch on my GSXR 1100 bled. I cracked it open to see if I was getting fluid through the line. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted November 13, 2023 Share Posted November 13, 2023 I cracked it open to see if I was getting fluid through the line. Okay then! That's good to hear Note the instructions here..... You crack the nut or open a FRONT bleeder in order to reset the rear system. You turn the key to RUN so the brake failure light can tell you when to stop pushing the pedal. If that spring is what's left of your warning light switch I'm not sure how you know when to stop... Link to comment Share on other sites More sharing options...
BigBrother-84 Posted November 13, 2023 Share Posted November 13, 2023 Okay then! That's good to hear Note the instructions here..... You crack the nut or open a FRONT bleeder in order to reset the rear system. You turn the key to RUN so the brake failure light can tell you when to stop pushing the pedal. If that spring is what's left of your warning light switch I'm not sure how you know when to stop... Not sure if this is relevant for this thread… Big Brother’s parking brake is fully functional, but the truck is also equipped with a pressure parking brake (was legal at that time). When I use this latter, the brake warning light stays “on” after I release it, until I “reset” the proportioning valve. I reset it by pushing on the brake pedal very firmly, then I feel a “click” on the pedal and the warning light goes off. 2-3 years ago, the light didn’t want to go off, and after some trials and tests I decided to replace the proportioning valve, everything went back ok. Link to comment Share on other sites More sharing options...
Dnix Posted November 14, 2023 Author Share Posted November 14, 2023 Okay then! That's good to hear Note the instructions here..... You crack the nut or open a FRONT bleeder in order to reset the rear system. You turn the key to RUN so the brake failure light can tell you when to stop pushing the pedal. If that spring is what's left of your warning light switch I'm not sure how you know when to stop... Thanks, I'm going to try this next. If it doesn't work I'm going to replace the valve. Link to comment Share on other sites More sharing options...
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