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

Video Transcript for Review of Demco Brake Actuator - DM5919

Today we're going to take a look at the replacement master cylinder with the inline solenoid for Demco disc brake actuators. Now this is a replacement master cylinder. It's designed for use with the Demco trailer brake actuators with electric reverse lockouts. This will work with the DA66B, the DA86, the DA91, the DA10, the DA16 and the DA20 models designed for disc brakes. Now this is a nice composite master cylinder. It's very durable and efficient.

Uses glass reinforced nylon construction to help resist rust and corrosion, and it's a very large reservoir which provides increased capacity for the brake fluid. And also what's nice, if you notice on the top here, it uses this automotive style diaphragm cap, creates a completely enclosed system to help prevent contamination of your brake fluid. Now this does include the electric reverse lockout that'll let you back up without actuating your trailer brakes. The master cylinder with this inline solenoid will install in your Demco disc brake actuator and it wires into your tow vehicle so that your trailer brakes won't activate when you shift your vehicle into reverse.Has two wires you can see here, one's a ground wire, one's a power wire, they're both yellow wires. So you can use either one for either function.

The power wire is connected to the reverse circuit on your trailer connector, and the ground wire connects to the ground connection. So what happens is when the vehicles placed in reverse, the electrical signal powers a solenoid which will prevent the brake fluid from getting to the brakes. Now this one is a non-bypass configuration, so when it's energized it'll just prevent the fluid from flowing anywhere. And one other thing I do want to mention on this is the reason this master cylinder is only for disc brakes, it's because it does not have the residual valve in the master cylinder like they use in the drum brake version. On drum brakes, the master cylinder does require that residual valve because it maintains approximately 10 to 15 pounds of hydraulic pressure on the hydraulic circuit, from the master cylinder to the drum brake wheel cylinders.

So this will reduce the time of brake activation by overcoming the pressure created by the drum brake return spring.So for disc brakes like this one is, you do not need that residual valve in there, because that extra pressure created will partially activate your disc brakes during highway travel, causing brake overheating and failure. So this one is for disc brakes only. If you do need the one for drum brakes, we do sell that separately on our website. It's part number DM5921. But that should do it for the review on the replacement master cylinder with the inline solenoid for the Demco disc brake actuators..