A "clicking" near the wheel ends?

At the end of this last week, me and my peers were given the assignment of "finding the clicking near the wheel ends of the of the Kenworth in our shop when the key was turned on." Knowing that this clicking would have to come from the electrical side of the air brake system, I was immediately drawn to the ABS part of the braking system. After doing a little research, I was able to identify the actual valve making the clicking and researched the part number. This lead me to the Bendix web site where I was able to identify the valve/s in question as the M-32 ABS modulator valve.  Valve shown below.

M-32 ABS modulator valve Part # 300386N replace with Part # 801666

This is the print out of the service data sheet I used to help understand just exactly what was going on inside the ABS modulator valve.

At this point I began to remove the ABS modulator from the truck so I could get an actual look at the diaphragms, springs, ports and solenoids or the insides of the valve.

The delivery lines that go to the air cans at each wheel end per side.

 The first step was to remove the air lines and electrical lines connected to the valve

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The supply line to the ABS modulator from the Relay valve.

The three pin electrical connector that supply's power to the solenoids.

After removing the ABS modulator from the truck, I began to take it a part.

This is the ABS modulator with the Exhaust port and solenoids removed.

The exhaust port cap

The two solenoids and there housing.

I think the main thing I learned from this assignment was what actually goes on inside one of these ABS modulators. Like how the solenoids are energized and move into the down position allowing the brakes to exhaust or how One solenoid is in the down position while the other is in the up position when the antilock application is held in position. There are lots of little details that go unnoticed and this assignment definitely clued me in on air brake and anti lock systems along with reminding me again that it is important to pay attention to small things and do the research and understand the system.

Week 7
Hours 180ish