Dnix Posted November 12, 2023 Share Posted November 12, 2023 Found my brake line that goes to the back of the truck was bad. The master cylinder was replaced before I got the truck. Emissions let me know that the rear brakes were not working. Opened up the rear bleeders and no fluid in them. So, putting the new line in today. What do I need to do to get fluid to the rear? 4x4 F150 replaced the line from the proportion valve to the rear line. Thanks Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted November 12, 2023 Share Posted November 12, 2023 Do you have a 150 or a 250/350? The warning light should have come on (unless it's been unplugged) You need to either push or pull the pin that holds the spool in place in the multi-function valve (brass "proportioning" valve) found below the driver. There was a bit of discussion about how this really works recently. I deleted my posts in that thread..... Link to comment Share on other sites More sharing options...
Gary Lewis Posted November 12, 2023 Share Posted November 12, 2023 Bad as in crimped or mashed flat? Or at least plugged? Once you replace that then I don't think you'll have a problem getting fluid back there. But maybe I'm missing something. Link to comment Share on other sites More sharing options...
Dnix Posted November 12, 2023 Author Share Posted November 12, 2023 Do you have a 150 or a 250/350? The warning light should have come on (unless it's been unplugged) You need to either push or pull the pin that holds the spool in place in the multi-function valve (brass "proportioning" valve) found below the driver. There was a bit of discussion about how this really works recently. I deleted my posts in that thread..... How do I do that do I have to take off the proportion valve completely Link to comment Share on other sites More sharing options...
Dnix Posted November 12, 2023 Author Share Posted November 12, 2023 Do you have a 150 or a 250/350? The warning light should have come on (unless it's been unplugged) You need to either push or pull the pin that holds the spool in place in the multi-function valve (brass "proportioning" valve) found below the driver. There was a bit of discussion about how this really works recently. I deleted my posts in that thread..... It's a 1986 f150 4x4 Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted November 13, 2023 Share Posted November 13, 2023 It's a 1986 f150 4x4 This was Gary's advice to the gentleman above you: "The pressure, differential, proportioning and metering valve are three different systems. (Figs. 4 and 5). There are three functions of the pressure differential valve: It delays full effectiveness of the front brake, it proportions pressure to the rear system, and it operates a warning system in case of malfunction. During heavy brake application, the proportioning valve reduces pressure to the rear brakes to avoid lock-up. The metering valve delays effectiveness of the front disc brake until the rear brake shoes are against the drum." But there's really not very much to the valve, so you might be able to clean it if the shuttle is stuck to one end. Here's an illustration of it: Link to comment Share on other sites More sharing options...
Gary Lewis Posted November 13, 2023 Share Posted November 13, 2023 This was Gary's advice to the gentleman above you: "The pressure, differential, proportioning and metering valve are three different systems. (Figs. 4 and 5). There are three functions of the pressure differential valve: It delays full effectiveness of the front brake, it proportions pressure to the rear system, and it operates a warning system in case of malfunction. During heavy brake application, the proportioning valve reduces pressure to the rear brakes to avoid lock-up. The metering valve delays effectiveness of the front disc brake until the rear brake shoes are against the drum." But there's really not very much to the valve, so you might be able to clean it if the shuttle is stuck to one end. Here's an illustration of it: If I remember correctly, Ford's instructions to center the shuttle are to STAND on the brakes with the engine running for boost. You don't have to be moving, but you need to put a lot of force on the braking system. However, if there is no flow to the rear, as would happen if the line is crushed, then the valve probably won't move. So the line has to be good first. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted November 13, 2023 Share Posted November 13, 2023 If I remember correctly, Ford's instructions to center the shuttle are to STAND on the brakes with the engine running for boost. You don't have to be moving, but you need to put a lot of force on the braking system. However, if there is no flow to the rear, as would happen if the line is crushed, then the valve probably won't move. So the line has to be good first. 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. Link to comment Share on other sites More sharing options...
Dnix Posted November 13, 2023 Author Share Posted November 13, 2023 If I remember correctly, Ford's instructions to center the shuttle are to STAND on the brakes with the engine running for boost. You don't have to be moving, but you need to put a lot of force on the braking system. However, if there is no flow to the rear, as would happen if the line is crushed, then the valve probably won't move. So the line has to be good first. 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 I just replaced the bad line. When I stand on the pedal should I have the rear pass bleeder open? Thanks for the info Yes, to bleed the brakes you need the bleeder open, otherwise the air compresses and just pushes fluid back when you let off the pedal. Link to comment Share on other sites More sharing options...
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