Lippert Components Disc Brake System For Trailers - Manual (Page 5)

Normally Closed - This solenoid valve is installed into a T-fitting from the master cylinder.
NOTE: A “three port” valve is also available to eliminate the T-fitting. A return line from the
valve, must be installed to return brake fluid into the master cylinder.
Advantages
♦ Eliminates the Disadvantages with “Normally Open” Valves.
Disadvantages
♦ Needs additional fittings, extra brake line, and requires drilling and tapping an access
hole in the master cylinder for the return line.
♦ Some OEM’s install the return line in the fill cap of the master cylinder. This may allow
a moisture to get into the brake fluid.
NOTES:
1. Solenoid valves may be one wire (internally grounded case) or two wires (ungrounded
case). On a two wire model, are not polarity specific.
2. Solenoid valves will have an IN and OUT to specify fluid flow direction. This
configuration must be observed when plumbing a solenoid valve.
3. Older hydraulic drum brake systems needed a 10 - 12 psi residual pressure
maintained to keep the wheel cylinder piston seals seated. To accomplish this, many
surge brake actuators have a check valve with diaphragm installed just inside of
master cylinder output port.
4. Disc brake systems subjected to residual brake line pressure will overheat the brakes
and hubs. Be sure surge brake actuator is designed specifically for disc brakes and the
check valve is rendered inoperative. Use an ice pick or awl to perforate the
diaphragm.
5. Never tow a surge braked trailer if the tow vehicle’s back up light circuit is ON at any
time other than when the tow vehicle transmission is in reverse.
6. When bleeding a system twith a normally closed solenoid reversing valve, bleed one
cycle minimu, with 12 VDC applied to the solenoid. The possibility of trapping air at the
valve will be eliminated.
Bleeding the Brakes
Step 1 - Pressurize the brake lines according to actuator manufacturer’s recommendations.
NOTES: -Air bubbles rise to the highest point in any fluid power line. Be sure the brake lines are
level avoid creating high points to hold air. Make sure surge brake actuator calipers are
as high as possible and actuator is as low as possible when during bleeding process.
-Use a small bleeder hose that will fit over the bleeder screw on one end and the other
end in a clear container of brake fluid to observe bubbling.
Step 2 - Install bleeder hose on bleed screw on first caliper bled. Bleeding process works best by
starting with the caliper furthest from the actuator.
Step 3 - When pressure is applied to the system, open the bleeder screw at the caliper, one turn.
Any air and pressurized brake fluid will be vented through the orifice in the screw.
Bleeding operation is complete when trapped air is purged from system. Be sure to close
bleeder screw securely after each compression stroke of the master cylinder.
Step 4 - When bleeding is complete, master cylinder reservoir should be full and all
bleeder screws are secured closed.
NOTES: -Bleeder screw should always point up.
-Bleed brake system thoroughly.
-LCI recommends the system to be bled after the first 100 miles.
5