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Replacement Master Cylinder w/ Inline Solenoid for Demco Actuators - Drum Brakes

Replacement Master Cylinder w/ Inline Solenoid for Demco Actuators - Drum Brakes

Item # DM5921
Our Price: $87.66
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Master cylinder with inline solenoid installs in your Demco actuator and wires into your tow vehicle so that your trailer brakes won't activate when you shift your vehicle into reverse. For use with Demco hydraulic surge-type drum brake actuator. 1-800-940-8924 to order Demco accessories and parts part number DM5921 or order online at Free expert support on all Demco products. Great prices and Fastest Shipping for Replacement Master Cylinder w/ Inline Solenoid for Demco Actuators - Drum Brakes. Accessories and Parts reviews from real customers.
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Demco Accessories and Parts - DM5921

  • Brake Actuator
  • Hydraulic Drum Brakes
  • Master Cylinder
  • Demco

Master cylinder with inline solenoid installs in your Demco actuator and wires into your tow vehicle so that your trailer brakes won't activate when you shift your vehicle into reverse. For use with Demco hydraulic surge-type drum brake actuator.


  • Replacement master cylinder is designed for use with Demco trailer brake actuators with electric reverse lockouts
    • Works with DA66B, DA86, DA91, DA10, DA16, and DA20 models designed for drum brakes
  • Electric reverse lockout lets you back up without actuating trailer brakes
    • Solenoid activates automatically when you shift into reverse
  • Inline solenoid configuration
  • Made in the USA

5921 Replacement Master Cylinder with Inline Solenoid for Demco Actuators - Drum Brakes

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Video of Replacement Master Cylinder w/ Inline Solenoid for Demco Actuators - Drum Brakes

Videos are provided as a guide only. Refer to manufacturer installation instructions and specs for complete information.

Video Transcript for Demco Master Cylinder with Inline Solenoid Installation

Hi there, Surge Brake Coupler owners with Demco's EZ connect version. Today we're gonna be showing you how to remove your coupler here, disassemble the master cylinder inside, remove it and replace it with the new one. The procedures are gonna be the same for both the drum brake version and the disc brake version. You do wanna make sure you're getting the correct one for your trailer and we're gonna be doing the drum brake version today is what we're gonna be showing off. We're just gonna take a look at it today and show you how to disassemble it to just do your typical maintenance. If your master cylinder, something happens to wear out over time, gets filled up with wrong type of fluid, lot of moisture gets in there, anything like that and you gotta replace it, we're gonna show you how to be able to service it yourself here.

So the first thing you would wanna do is get the fluid out of the system. So I actually took the bleeder screw at the back loose, but you could also take the loose right here at the back of the actuator. It was just easier to drain it into a container towards the rear, a little bit closer to the ground 'cause you really don't wanna get brake fluid on any painted surface. It is quite corrosive to paints and stuff. Your paint will come off of there.

It'll discolor them. So just try to avoid that. We did place a napkin under here for when we take that loose for any of the fluid that's left in there. When you do drain it, I do recommend that you pop the cap off here. That'll let it drain a little bit faster.

Air can get in this way and let it drain out. So we've already let ours drain so we should be pretty dry at this point. So we're gonna head over to this side and we're gonna get our hoses disconnected here and our wiring disconnected. Then we will have to take out the bolts here that actually hold the entire coupler onto the trailer because the actuator inside is not just gonna slide out of there. Now there are quite a few different versions of this particular surge actuator.

You can get it in different weight ratings with different ball sizes. The particular one we're working on here today is gonna be a 7,000 pound version with a two-inch ball. We're also using the one that has the electric lockout for for backup. That's nice for these boat trailers 'cause when you put it in reverse, the reverse signal from your vehicle for the reverse lights will actually activate on this circuit. The other one just goes to ground there and that'll activate the solenoid and prevent it from being able to activate the brakes. That really comes in handy when you go to launch your boat 'cause if you're trying to back down a ramp and the brakes are applying, it's gonna make a very difficult time. So I do recommend that. They do offer these also in manual versions with a manual lockout. So you have to get out and actually pull the lock out to activate it so you can get them in two different styles. If you have the style with the electric lockout, you'll have this additional cover here that protects that component. If you have just the regular manual lockout, you won't have this cover on here. The cover does install onto two of the bolts that actually holds the master cylinder into the coupler there to the coupler assembly. So we are gonna remove those. You're gonna use a 3/8 socket to take out these two bolts. We're gonna leave the other two in there for now. If you don't have the electric lockout, you can skip this step where you'll have access to the back there. So we'll just zip these outta here real quick and then we can get that plate out of the way. And if you do have like a manual version or something and you're wanting to upgrade to an electric version, you can actually purchase this kit here at etrailer that comes with the solenoid as well as the cover. So you can add that in line. You would've to bleed your brakes after introducing this component 'cause you're gonna have air in this section so you have to bleed it all the way back again. We will be covering how to bleed your assemblies, just keep that in mind. So now, we did put a rag under there just in case. We're gonna make sure we hold here 'cause we don't wanna damage our solenoid for the electric lockout. So we're gonna use a 9/16 to hold and then we're gonna use a 3/8 line wrench to take off our line. If you look at the difference here between the line wrench, you've got a lot more surface area there. It goes almost all the way around. You can't just slide it on like a regular box end wrench slides on. It's designed to be able to slide over a line and get that increased contact so that way you don't strip out the nut for your lines 'cause it is gonna be a softer metal than what a lot of the traditional metals are that you would use for like the actuator bolts and things, or not the actuator, but the coupler bolts and stuff like that. So this metal's a lot softer, so a regular wrench you can strip it out and round that off a lot easier. So you gotta make sure you got one of these. You can purchase line wrenches here at etrailer if you do need some. So we're just gonna loosen this up. Now again, we've already drained it at the back at one of the bleeder screws or you could take a line loose at the back however you wanted to do it. I recommend that just 'cause you don't want brake fluid to get on any of your components and it's just easier to keep control of where the brake fluid goes. So we got our line slid out of there. We're just gonna back that out of our way. I'm gonna tuck it off to the side so that way it doesn't potentially drip on the frame. If we can, maybe we'll use, I wanna keep that rag there. Here we go, that'll keep it away. So we're gonna remove our ground wire. You can follow that over. It goes to ground right there. We're gonna use a 5/16 or an eight millimeter socket to remove this, and this can be different sizes. This is just a self-tapping fastener in there so it's not uncommon that it could be a 3/8 or 10 millimeter. So we'll move that out of there. Make sure you save your fastener 'cause we are gonna be putting on another one that does have the lockout. And then the other one in here we're gonna just disconnect. So we're trying to see where they've been connected and we'll just cut our wire at an appropriate spot. So we can see that's all there. Looks like this is likely where it was wired in last time. So we'll make sure that we've got enough wire length. We'll probably snip it off here and then we'll clean that up. So we're just gonna make an incision with our snips here. And it looks like this is also just a redundant ground that's tied into that ground wire. So we'll be reconnecting to that. So we're gonna leave ourselves a little bit extra there to be able to make that connection. So we're gonna snip it probably back there a little bit just so we can still access it. All right, so we've got our hose off, got our wires off. We can now pull this whole assembly off. I'm gonna put the cap back on, so in case there is a little bit trace in there and we flip it over, it's not gonna get all over 'cause you really don't wanna get this on anything. Try not to get it on your hands, brake fluid hygroscopic, which means that it absorbs moisture so it will dry your hands out really bad. It's bad for painted surfaces and a lot of stuff so just try to stay away from that. Keeping that stuff off any surface. You don't want to potentially get damaged. So now we're gonna use our gun here to remove the fasteners that are holding the actuator on. We have three here and on the opposite side in the same location you'll also have three. Ours here are gonna be a 3/4 in size for both the nut and the bolt. Some are passing through with the nut on the inside. Some of the bolt is passing from the inside outward with the nut on the outside. So there's an opening here at the bottom. You can take your wrench, slide it up in there. Sometimes you can't get on the bolt right away, but as you go to loosen the bolt, you should be able to slip that wrench on there to hold. Here we go. And we'll just pull that fastener out of there. And we're just gonna repeat this for the remaining fasteners. Make sure you fish all of your hardware out of the frame 'cause we are gonna be reusing that to resecure it. So after we loosened a few turns with the wrench and it got a little play in it, we are able to get a thin wall socking on there now so we can zip that out with the gun instead of having to waste a bunch of time with the wrench the whole time. And then of course our last one here should be easy to access so we'll zip that off of there as well. And then we're gonna head over to the other side and remove the same fasteners over there. So that last fastener we actually removed that was sticking from the inside outward was a carriage bolt inside of a spacer like this. So you might see that as well. That is nice because you don't actually have to put a wrench on the inside to hold. The spacer grabs on the square there and it'll just hit inside the frame so you can just zip that nut off and then pop that bolt in. Now when you go to pull out that last fastener, you wanna make sure you're supporting your coupler 'cause it potentially could fall. It's heavy towards this side. So that last bolt, make sure you're holding that and then we can slide this whole piece off of there and then set that down. So our actuators held in by the two remaining fasteners or if you didn't have the electric lockout, you would've still two more in there. But since we had those remove that cover off of there, so we could easily access these parts. So we're gonna switch back to our three eight socket to remove those two fasteners there. And our actuator, you may have to remove the cap. It looks like it would fit down in there, but it's hanging up just a little bit so we'll just slide it off of there. And so then slide out the back. So here we've got our original actuator sitting next to the replacement actuator. And again, there was nothing wrong with this one, we're just showing you how to replace it in case you needed to. One of the things you'll notice is that the new actuator does come with new bolts and we'll show you why here. Keep that up right a little bit. These I slid back in here because this is actually what holds the master cylinder here together, it's these two bolts. Let's take a look inside. We slide off the top. You can see it does have a gasket that seals. It's just a cork style gasket. So we can go ahead and take our old actuator here. The plunger here we're actually gonna reuse. That'll slide down into the assembly so you can slide that out and that'll slide right into your new one here. So just line it up, just gently slide it in there. This is just the dust boot that you're sliding it in and then it will go into the cylinder for the master cylinder there, for the actual application plunger. If we go ahead and pull the dust boot off, if you want it to just see on the inside there, there's the bore that the rod will slide in to activate the master cylinder. It does have a snap ring on there so if you have leaks and seal or something like that, you could disassemble it further to replace it. But honestly once you get down this far, putting in a new unit is a good idea. Maybe I would replace this top seal if it was seeping around there or something, but I wouldn't do too much more disassembly 'cause this is when you start getting into the actual function of the unit here as far as applying the pressure and getting proper amount of pressure to your brakes to activate them. So I would avoid messing with that, but this is just the top seal up here. So if you got a little bit of seeping, leaking a little bit of air, that is replaceable up there by removing the bolts like we showed you. So we're gonna get this guy set aside now, clean up some of our mess. And before we go to slide it back into the assembly, we do have to remove all the bolts. We're gonna use all the new bolts that it comes with. You do wanna be careful once you've removed these bolts 'cause it is just like the other one. That's what's holding the top cover on there and I'm keeping downward pressure on the top cover. So I really don't wanna separate the new unit if I can. Keep those pieces together, maybe knock any little bit of debris away from there. We don't want anything to go down into the assembly. You saw how small the hole was on the other one so you wanted to make sure you keep any contaminants out of there. So we're just gonna pinch that, hold it together. You can see the nuts for the bolts when we screwed it in place. They're down there and their little slots. They're held in there pretty tightly into that slot. It doesn't feel like it's gonna be able to just fall out of there or anything. I could probably pry it out if I wanted to, but we don't really want to. We want those to stay there. So now we'll slide it into our assembly here. All right and now we're gonna reinstall two of the fasteners, the ones towards the coupler end. Always make sure you hand thread your bolts first to make sure that you do get them started in the nut. You don't wanna cross-thread it. So each one I could feel started. Now we'll run them back down And don't run these down too tight. This is just a plastic assembly. We'll go back and make sure we've got proper tension on the bolts, but for now just run them down until they're snug just to hold it up in there with minimal plays, that way everything's lined up. It's not a bad idea too just to take two fasteners and slide them in there, but we're not gonna tighten them down. We just wanna make sure that our holes are lined up for us. So looks like everything's lined up there so we'll pull them back out. Now you're probably wondering how am I gonna access this thing to push on the actuator without hooking it to my trailer We'll be showing you that. This cover here is gonna be removable. You can see on the sides, you can almost push in a little bit. There are like little tab that you would push in there. Surprisingly strong plastic. There we go. And if you wanted you could remove that first. It does make it a little bit easier lining this piece up, but you can see it's got a big U there so it's pretty easy to get that to line up when you're sliding it together. So at that point now we've got the new one installed. The one that we installed is for a drum brake system. That's why we chose this actuator. But the procedures to replace it for a disc brake system from Demco is gonna be the exact same as far as sliding it out. You just gotta make sure you have the appropriate actuator for the application. So if you have drum brakes, make sure you're using a drum brake one. If you have disc brakes, you would wanna use a disc brake one, whichever. So with our new component in there, we're gonna lift it back up, slide it back into position, and line up all of our fastener holes. Well, then just reinstall our fasteners. I'm gonna probably start with this forward one just to get something in there to hold it 'cause we don't want it to fall off on us while we're working. So one of the things I did notice is I was having a difficult time getting the bolts to line up and without these back two ones in there leaving that cover off, the new actuator or the gasket hasn't really been crushed yet. So it's sagging it down just a little bit here in the back making it difficult for the bolts to line up. So go ahead and run your bolts down just a little bit. Nothing crazy tight, just enough to draw it up some. Now we'll grab our fish wire and this is what a fish wire looks like there. It's a wider gap than what we want for the bolts we're using, but we can make this work. So you're gonna stick that in the hole that had the carriage bolt if you are using carriage bolts and then you're gonna bring that out the front just like that. I always like to take at the very end of my fish wire and I'll put a 90 degree bend in it there. That just helps keep it from falling out of the hole while I'm getting the other side threaded in. And if you got one here that you're trying to like reuse multiple times, you'll wanna find where the thread starts and then follow that path while pushing in on the wire and that way you can get it to just glide right in the path and you can see there that it's threading right on there for us. You do gotta keep it pressed inward if it's a reuse 'cause you don't get any of this stuff with the new replacement master cylinder there or actuator and that's on there probably far enough that we can do what we need to do to get it pulled through. So we're gonna push our bolt up into the frame, line that up and pull our fish wire. Sometimes it helps if you grab one of your screwdrivers and use that with a little bit of force on the inside 'cause this is farther than my fingers can reach. So I can stick this in there. And just assist it 'cause it's gravity's taking place and pushing it at an angle. And then when you finally get it lined up there, it will just pull right on through. After you got it pulled through, go ahead and take your fish wire off of there. Try to save it if you can 'cause we wanna reuse that on the other side. Also, try not to let the bolts want to push back into the frame. We'll then put a washer and a nylon locking nut on the outside. So we're gonna go ahead and I'm not gonna tighten it all the way down yet because some of the other holes for the other side and stuff may not be lined up very well. And if you snug it all the way down, you're gonna have a more difficult time maneuvering it to get those bolts to line up. We are gonna get the carriage bolt in on the other side first and then we can go back and finish up these bolts. This one here is just hanging out inside there loosely to make sure this actuator can't fall off there while we're working. It's actually doesn't even have a nut on it 'cause with it sticking through, sometimes it gets in the way a little bit of your feeding your carriage bolt with the spacer on it. So being able to move it up and down a little bit is convenient. All right. We got our carriage bolt in on the other side and our nuts started on each one. So now we'll reinsert these bolts. The one that had the cut washer, needs to go down there at the bottom. And then on the inside we're gonna follow that up with a flat washer and then a nut to secure that on the inside. So it's a little difficult to see in there. So just make sure you slide your hand in there, slide that washer on first. And then when you're holding the nut in there, it's really difficult to actually turn the nut so it's easier if you turn the bolt here to get it to thread into the nut. So you might have to push it out just a little bit. Get it hand tight. There we go. And then we'll just move on to this one. I've already got it slid through there with this washer on it. So of course on the inside it's gonna get a flat washer and a nut as well. And sometimes it's a little easier if you pull it out just a little bit. Just depends on how your fingers can fit up in there. And you'll probably also want to turn the nut, I mean turn the bolt to get it threaded into this nut as well. All right, so we've got all these hand tight. We're gonna do the other side the same way. Get all those hand tight and then we can come back with our tools to tighten it all down. We'll now go back and torque our bolts to the bolt manufacturer specification. If you're unsure who manufactured the bolts, there's plenty of charts online where you can look up by bolt diameter, thread pitch, and grade and you can usually find a torque spec based on those parameters that you can utilize to torque these down. Grade 5 bolts are what is recommended for these. For your inner ones, you're likely gonna need to hold the nut with the wrench while torquing. Take our line and reinstall it and start it by hand. Go as far as you can by hand first 'cause again we don't wanna cross-thread anything, especially once you get this far. So we got that in there now. Now you need your wrench to hold this 'cause we don't wanna damage the solenoid. So hold that and then use your 3/8 wrench to snug it down and of course your line wrench. And then sometimes I'll do is with this being a flex hose, I'll turn the flex hose. This direction twists the flex hose beforehand, so that way when I go to snug it down, it twists the hose back up right. So we're gonna loosen it just a hair, twist our hose just a little bit, snug it down by hand, and we'll put our wrench on there and snug it down with our 3/8 wrench. There we go. That's decently snug. We'll put maybe a little bit more on it. And you'll notice that the line has a nice gentle curve in there. We're not twisting the hose. The pre-twist we did allowed it to bend back up right and go down. Hook up our lockout solenoid, they do come pre-stripped, but you probably wanna strip back just a little bit more. That'll be a difficult amount to be able to attach to. So one of course is gonna go to ground and we've got our ring terminal here that we can reinstall into the location there. And then the other one here, we're gonna clean this up and reattach it back into the trailer there. So we're gonna just go ahead and strip these back just a little bit more. Now they're both yellow because it doesn't matter which one goes where. Just one of them has to go to ground and the other one has to go to the reverse lockout circuit or that would be the reverse light or backup circuit from your vehicle. Strip that one back and we'll strip this one back just a little bit more. All right. So we'll go ahead and hook up our ground first since it's right here. Strip that one back. I'm gonna take a heat shrink butt connector, slide it over the end there and crimp it down. And I do recommend a heat shrink butt connector because we're outside the vehicle. It's on a boat trailer. This is definitely gonna be exposed to moisture. So we will seal up the ends with our heat gun once we've got our connections made. And based on length, I think I'm gonna use the one that's a little bit higher up on top for the ground one. Just to make sure I got enough length wire to reach down here to our other circuit. This one's just a little bit closer. And we'll get the electrical tape off here, get this one cleaned up and we'll get our other one attached the same way back to this circuit. With our heat gun, we'll seal those up. We can now go ahead and reinstall our ground wire. We'll push that wire loom back on there, line it back up with the hole, reinsert it and then use our 15/16 or eight millimeter to run it back down. Make sure it can't rotate. We got a good ground and now we can reinstall the cover onto the back here covering this stuff up. This does need to be done before you go to fill up the fluid because without these four fasteners tightened down, it can pull in air around that gasket that we saw when we had it disassembled. So we'll just line that back up there, put our fasteners back down in there, make sure we start them by hand. And then go ahead and run them on down. And now we just wanna snug these back up 'cause we didn't have them all the way fully tightened. Now you don't wanna tighten them very tight 'cause again it is just a plastic housing. It threads into a metal nut, but you don't wanna compress it too far. So just stay on the lighter side. If you have an inch pound torque wrench, you would probably wanna use that and keep it fairly low. So this is a drum brake set up here and you're gonna find your bleeder screw on the wheel cylinder where you hooked up your line. It should be right next to it. Now if you we're working on a disc brake setup, I've got a sample caliper here to show you typically something like this. And you'll notice on the disc brake set up versus where the line would enter and here's the bleeder screws. Now not all disc brake calipers are gonna have two bleeder screws, but if they do have two bleeder screws, you would always wanna use the top bleeder screw when bleeding your brakes. And the size of the bleeder screw can vary. It looks like this is probably 5/16 for this Kodiak caliper. And over on our drum brake here, I know that that's gonna be a 3/8 in size. So we're gonna be bleeding drum brakes. But again, the procedure's the same, it's just the location of the bleeder that you need to really pay attention to and always use the top one. With drum brakes, you shouldn't have multiple. There should just be this one. And when I do this, I always wanna start at the wheel that is furthest from the actuator. So we're gonna go ahead and start on the passenger side rear here. That's typically the furthest one, but just depends on where your actuator's located. If it's in the center, the left or the right. So we're gonna start on this one though 'cause this is the typical. Usually the furthest rear for us is gonna be the furthest to the rear. So now we're gonna go ahead and take our little cap off of there. Don't lose your cap. It's nice to have that on there to keep dirt debris and stuff from filling up in here and clogging up your bleeder screw for future maintenance and things like that. So we're gonna go ahead and loosen this up. Now we haven't filled it with fluid yet, but we're gonna do gravity bleeding first to let nature and gravity do most of the work for us here. Minimize how much we have to pump our system. So I'm opening up the bleeder screw and I went ahead and pulled it open just a couple of threads there. In most cases, you don't need to open it that far when bleeding, but when doing gravity bleeding, a little bit extra opening helps that flow just work naturally better. So you may also wanna take a rubber hose and place that on there and bring it down to your pan because brake fluid can be pretty bad for painted surfaces, wearing off the paint and stuff. So we're gonna also grab a little hose and have that go down to our drain pan here just to minimize exposure of brake fluid on our components. All right. We've slid our hose on there to direct it down into either container or a pan. We do have a container that we just rigged up here. This is a just an old sports drink bottle. So this works out fairly well for something like this. But again, we have a pan under here as well just in case the hose does drip a little bit, we're catching it. So now we're gonna head up to our actuator and we're gonna go ahead and fill it up and then let nature take its course and let gravity do the best it can to start pushing the air from the front, back through our lines and out, and getting that fluid there. Now even though we are gonna be gravity bleeding it, you are still gonna have to do some pumping. Gravity's not gonna do all the work, but it will minimize how much physical labor you have to do. So here we are at the front now, I went ahead and took the cap off of our actuator. If you look at the top here, you'll notice that it tells you what specification of fluid to use. You can use either DOT three or four fluid in this particular setup. We're gonna be using DOT 3 today. Again, you can use either. You do wanna make sure that you're using brake fluid from a new container 'cause brake fluid is hygroscopic, which means it absorbs moisture. So even an open container that's been sitting for a while can actually draw that moisture out of the air. And the more moisture that is in your brake fluid, the lower the boiling point is in the fluid and we don't want fluid to boil. We're gonna be careful not to spill the fluid and go ahead and fill it up. And since we're gonna be bleeding it, we're gonna get it pretty close to the top 'cause we are gonna be losing fluid as it goes through the system and out towards the container that we have at the back. All right. So we've got it filled up there. We're gonna go ahead and let gravity do it, take its course. So you're probably gonna see some bubbles there as it starts to make its way through the system. Some of the air's gonna come to the top here. Some of the air's gonna get pushed back through that open bleeder screw we have towards the rear. We went ahead and let it gravity bleed for a while. We ended up not really getting any fluid out the back. Sometimes you do, sometimes you don't. Sometimes lifting up the front of the trailer to make it the highest point, which it should already be the highest, but sometimes lifting it up a little higher can help speed up that process or get it started. But in the event that it doesn't, no big deal. You can still pump it manually. So we've got it all topped up here. After you've got it topped up, it is a good idea to put the cap on. In a lot of cases, you don't want the cap on while bleeding, but we we're trying to minimize how much mess we make here. So keep it from squirting back out of there. Our assistant is gonna push in and we're gonna be at the back and we're gonna open up the bleeder screw. So we're gonna go ahead and head to the back now to the wheel and we'll communicate with our assistant here to press. And what we want to happen is we want our assistant to press it in. We'll open the bleeder screw, let the fluid come out or air, whatever we get out of it. We'll close it. Our assistant will then release and then he will then press in and we will just repeat that process over and over. But we never want to have the bleeder screw in the back open when our assistant is releasing 'cause that's gonna draw air back in our bleeder screw. Go ahead and push it in. Our assistant's gonna press. We're gonna open and there's our fluid coming out. I can see a few air bubbles there. So we're gonna go ahead and close it back up. Okay, you can go ahead and release. Our assistant's now released. So then what we're gonna do is we're gonna now have him press it again and we're gonna open it again and just keep rinsing and repeat until we get a solid stream of fluid out. Every few presses, you may wanna recheck your reservoir and refill the fluid 'cause you don't want it to go empty. If it goes empty up there, it's now drawing in air from the front and we don't want any air in our system. So go ahead and press. There you can see all that air shooting outta there. So we're gonna close it. You can go ahead and release. And now that he's released, you can go ahead and press again. And that was a pretty good solid stream we've got there. So we're gonna double check our reservoir, probably hit this one, one or two more times, then we're gonna head over to the other side and do that one. And you just rinse and repeat for however many wheels that you have until you get a solid stream out of each one. Once you've got everything bled, you can go ahead and reinstall your wheels. If you purchased new drums and hubs from us, they do come with new lug nuts for half inch studs. So you can utilize those as well. We can go ahead now and tighten them down. The new nuts that it comes with is gonna be a 21 millimeter in size. And when tightening them down, you wanna do it in a star pattern. This will ensure the wheel draws in evenly and the tapered side of the nut should face the wheel with the flat side facing outward. And once you get this back on the ground, you'll wanna make sure you torque your lug nuts to the manufacturer's specifications. And that completes our look at Demco's replacement drum brake master cylinder..

Customer Reviews

Replacement Master Cylinder w/ Inline Solenoid for Demco Actuators - Drum Brakes - DM5921

Average Customer Rating:  4.8 out of 5 stars   (4 Customer Reviews)

Master cylinder with inline solenoid installs in your Demco actuator and wires into your tow vehicle so that your trailer brakes won't activate when you shift your vehicle into reverse. For use with Demco hydraulic surge-type drum brake actuator.


The whole staff at etrailer bent over backwards to make sure I was satisfied with the installation of brakes on my trailer. Have made several purchases from them always satisfied with parts and service. Special credit to Jamie great to deal with. Answered all my questions and was very knowledgeable.



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See what our Experts say about this Demco Accessories and Parts

  • Can the Demco 5918 Replacement Master Cylinder for Disc Brakes be Used for Drum Brakes.
    The Replacement Master Cylinder w/ Bypass Electric Lockout for Demco Actuators - Disc Brakes # DM5918 is for disc brakes only. You will not be able to use this with your Demco actuator for drum brakes. Instead, you need the Replacement Master Cylinder w/ Inline Solenoid for Demco Actuators - Drum Brakes # DM5921. This works with DA66B, DA86, DA91, DA10, DA16, and DA20 models designed for drum brakes.
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  • Which is Better Master Cylinder Lockout Design for Demco Surge Actuator # DM5920 or # DM5921
    The part # DM5921 is a replacement master cylinder with electric lockout that fits your Demco DA20 coupler which has a lockout design that basically stops the hydraulic pressure from getting to the brake assemblies whereas the # DM5921 has a bypass design that directs the fluid/pressure back into the master cylinder when locked out. The bypass style is easier on the master cylinder since the pressure has somewhere to go so if you wanted the best design this is the way to go.
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  • Replacement Parts Available For a Demco DA10 Surge Brake Actuator
    We do have a large selection on replacement parts for a Demco DA10 surge brake actuator. Replacement Shock # DS12426 Slide Repair Kit # DM5943 Replacement Drum Brake Master Cylinder w/ Bypass Solenoid # DM5920 Replacement Disc Brake Master Cylinder w/ Bypass Electric Lockout # DM5918 Replacement Drum Brake Master Cylinder w/ Inline Solenoid # DM5921 Replacement Disc Brake Master Cylinder w/ Inline Solenoid # DM5919 Reverse Lockout Solenoid # DM11993 Replacement Solenoid Cover # DM11674-95 Replacement...
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Employee Lindsey S
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