gaveasky Posted June 14, 2023 Author Share Posted June 14, 2023 I see now that the early cast iron master cylinders break at 8500. This is so Ford can include 8,600 gvw trucks .under federal guidelines. If you look at the later (87-93) masters with aluminum housings and plastic reservoirs the break moves down to exclude "light" 250's. I realize all this pedantry may be confusing but it really matters when you start swapping parts to get a 'factory upgrade' I see! If I understood correctly then, a later model master cylinder would fit directly onto my current brake booster housing and be a better option, and all I have to do is switch a couple of lines around. If this is the case and considering the specifications of my vehicle, would any of you kindly recommend which one I should buy from Rockauto? I think I will place an order for a few things incl. glow plugs since I am in Canada and it would be smart to save on shipping. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted June 14, 2023 Share Posted June 14, 2023 I see! If I understood correctly then, a later model master cylinder would fit directly onto my current brake booster housing and be a better option, and all I have to do is switch a couple of lines around. If this is the case and considering the specifications of my vehicle, would any of you kindly recommend which one I should buy from Rockauto? I think I will place an order for a few things incl. glow plugs since I am in Canada and it would be smart to save on shipping. Well, that's how Gary and I feel. (along with other forum members like Cory and John on their 150's) But as I said, you need the residual pressure valve, and while the ones that U-Haul offered had this valve the ones I see on RA don't seem to.... I think I need to cross the Motorcraft number or at least find the stupid check valve before I can recommend parts swapping. Edit: That residual pressure valve is E7TZ-2C161-B, and over $50 by itself!!! That's why I'm so determined to find a master that includes it. Link to comment Share on other sites More sharing options...
Gary Lewis Posted June 15, 2023 Share Posted June 15, 2023 Well, that's how Gary and I feel. (along with other forum members like Cory and John on their 150's) But as I said, you need the residual pressure valve, and while the ones that U-Haul offered had this valve the ones I see on RA don't seem to.... I think I need to cross the Motorcraft number or at least find the stupid check valve before I can recommend parts swapping. Edit: That residual pressure valve is E7TZ-2C161-B, and over $50 by itself!!! That's why I'm so determined to find a master that includes it. Maybe this will help. In this post in Master Cylinder Upgrade Part Numbers Larry/ratdude747 said: Working on a brake repair/upgrade for my 1984 using a later model (Bricknose/Aeronose) master cylinder. Right now I'm getting my butt kicked when it comes to brake bleeding (Long story short: Vacuum bleeders suck, waiting on a pressure bleeder to come in). In the mean time though, I do have some information to share. First off, Raybestos makes a new master cylinder for the later application that includes the residual pressure valve, the reservoir, and the reservoir level sensor, specifically MC39634: https://forum.garysgaragemahal.com/file/n120071/IMG_20220615_162737__01.jpg As of this writing RockAuto has them for $33 before tax and shipping (no core)... which pending testing, is a great deal. One thing I plan to (eventually) do is wire the reservoir level sensor into the brake warning circuit (parallel to the existing proportioning valve switch). The connector to do this is Motorcraft WPT-446; I de-pinned the center terminal (which on my pigtail was double wired) and used the outer two pins. The third pin is tied to one of the outer pins; this is used on later model vehicles to tell the ABS controller if some twit has unplugged the sensor to bypass a low level condition (which the ABS controller needs to know about; activating ABS with a brake line failure is a great way to make a bad situation worse!). Before going this route, I didn't know the Raybestos MCs came with all the trimmings (RockAuto's pictures showed there not being a residual pressure valve) so I opted for a used eBay Ford unit... which was a complete loss. Nothing worked... it was seized on arrival and the front brake circuit wouldn't bench bleed. Also, the reservoir sensor was toast... more on that below. If one needs to replace one of these reservoir sensors: you'll read online the only fix is to replace the entire MC (or the reservoir at least). Not technically true, as there are two options: 1. Find an NOS sensor. It's Motorcraft E6DZ-2L414-A, usually found on ebay for around $70 (way more expensive than a Raybestos MC with a new sensor, but if you're a purist dead set on a new sensor, that's the way you'd need to go) 2. Rebuild the sensor. The sensor is merely a potted reed switch; through some hacking away, I was able to dissect my faulty sensor (which seemed to have a bad solder joint, but I broke the switch tube): https://forum.garysgaragemahal.com/file/n120071/IMG_20220611_210430__01.jpg https://forum.garysgaragemahal.com/file/n120071/IMG_20220611_215725__01.jpg A better way to do this may be to boil the sensor in a pot of water; the potting compound loses it's adhesion and softens with just a little heat, which would probably allow one to yank the tray out of the tube and pick off the compound without cutting or scorching anything. I made the mistake of using a MAPP torch on mine to soften the compound... even lightly used, it melted the plastic tray. The switch tube I used to repair mine is a 14mmx2mm 0.55A unit: https://forum.garysgaragemahal.com/file/n120071/IMG_20220615_193509__01.jpg If I were to use this switch, I'd pot it with some hot glue... but since I have a new one (that works great), I'll use that instead! Master cylinder installed (I had to ditch the line bracket and re-bend the lines as the front and rear brake circuit positions are switched): https://forum.garysgaragemahal.com/file/n120071/IMG_20220615_192433.jpg Now if I can get the darn things to bleed... Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted June 15, 2023 Share Posted June 15, 2023 Maybe this will help. In this post in Master Cylinder Upgrade Part Numbers Larry/ratdude747 said: Working on a brake repair/upgrade for my 1984 using a later model (Bricknose/Aeronose) master cylinder. Right now I'm getting my butt kicked when it comes to brake bleeding (Long story short: Vacuum bleeders suck, waiting on a pressure bleeder to come in). In the mean time though, I do have some information to share. First off, Raybestos makes a new master cylinder for the later application that includes the residual pressure valve, the reservoir, and the reservoir level sensor, specifically MC39634: https://forum.garysgaragemahal.com/file/n120071/IMG_20220615_162737__01.jpg As of this writing RockAuto has them for $33 before tax and shipping (no core)... which pending testing, is a great deal. One thing I plan to (eventually) do is wire the reservoir level sensor into the brake warning circuit (parallel to the existing proportioning valve switch). The connector to do this is Motorcraft WPT-446; I de-pinned the center terminal (which on my pigtail was double wired) and used the outer two pins. The third pin is tied to one of the outer pins; this is used on later model vehicles to tell the ABS controller if some twit has unplugged the sensor to bypass a low level condition (which the ABS controller needs to know about; activating ABS with a brake line failure is a great way to make a bad situation worse!). Before going this route, I didn't know the Raybestos MCs came with all the trimmings (RockAuto's pictures showed there not being a residual pressure valve) so I opted for a used eBay Ford unit... which was a complete loss. Nothing worked... it was seized on arrival and the front brake circuit wouldn't bench bleed. Also, the reservoir sensor was toast... more on that below. If one needs to replace one of these reservoir sensors: you'll read online the only fix is to replace the entire MC (or the reservoir at least). Not technically true, as there are two options: 1. Find an NOS sensor. It's Motorcraft E6DZ-2L414-A, usually found on ebay for around $70 (way more expensive than a Raybestos MC with a new sensor, but if you're a purist dead set on a new sensor, that's the way you'd need to go) 2. Rebuild the sensor. The sensor is merely a potted reed switch; through some hacking away, I was able to dissect my faulty sensor (which seemed to have a bad solder joint, but I broke the switch tube): https://forum.garysgaragemahal.com/file/n120071/IMG_20220611_210430__01.jpg https://forum.garysgaragemahal.com/file/n120071/IMG_20220611_215725__01.jpg A better way to do this may be to boil the sensor in a pot of water; the potting compound loses it's adhesion and softens with just a little heat, which would probably allow one to yank the tray out of the tube and pick off the compound without cutting or scorching anything. I made the mistake of using a MAPP torch on mine to soften the compound... even lightly used, it melted the plastic tray. The switch tube I used to repair mine is a 14mmx2mm 0.55A unit: https://forum.garysgaragemahal.com/file/n120071/IMG_20220615_193509__01.jpg If I were to use this switch, I'd pot it with some hot glue... but since I have a new one (that works great), I'll use that instead! Master cylinder installed (I had to ditch the line bracket and re-bend the lines as the front and rear brake circuit positions are switched): https://forum.garysgaragemahal.com/file/n120071/IMG_20220615_192433.jpg Now if I can get the darn things to bleed... Larry has a 150, so that master cylinder part number is wrong for an 8,600 gvw truck. (see what I said about 1 1/16" bore) The residual pressure valve may be correct. I know the Ford P/N I posted is good for '87-'93 Link to comment Share on other sites More sharing options...
Gary Lewis Posted June 15, 2023 Share Posted June 15, 2023 Larry has a 150, so that master cylinder part number is wrong for an 8,600 gvw truck. (see what I said about 1 1/16" bore) The residual pressure valve may be correct. I know the Ford P/N I posted is good for '87-'93 Oops, I missed that you are looking for one for an F250. Sorry. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted June 15, 2023 Share Posted June 15, 2023 Oops, I missed that you are looking for one for an F250. Sorry. The only one I see that includes the residual pressure valve is from Dynamic Friction. (Link) But it also says "without speed control" so it doesn't have the port on the front for the switch. I don't think that's an issue with older trucks that came with the cast iron master, but IDK for sure. Gary??? Link to comment Share on other sites More sharing options...
Gary Lewis Posted June 15, 2023 Share Posted June 15, 2023 The only one I see that includes the residual pressure valve is from Dynamic Friction. (Link) But it also says "without speed control" so it doesn't have the port on the front for the switch. I don't think that's an issue with older trucks that came with the cast iron master, but IDK for sure. Gary??? Right. It actually simplifies things as you don’t need to plug that port. Link to comment Share on other sites More sharing options...
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