Delivery Check Valve Cleaning Procedure

If, after bypassing the air dryer, the system pressure still does not build, use the following procedure to remove, clean, and reinstall the delivery check valve.

(Note: This is only required if system pressure does not build after temporary bypass is completed.)

Refer to Figure 7 throughout the following procedure. De-pressurize the air brake system following the general safety precautions outlined elsewhere in this document. Also, always de-pressurize the air dryer purge reservoir before servicing the air dryer by slowly loosening the fitting that connects the air compressor discharge line to the air dryer inlet port.

This procedure does not require removal of the Bendix® AD-9si™air dryer from the vehicle.

1.Remove the delivery check valve cover, located directly above the delivery port (OUT 21).

2.The spring/delivery check valve can now be removed.

3.Remove and retain the o-ring from the check valve body.

CLEANING & INSPECTION

1.Use a suitable solvent to clean all metal parts, and use a cotton swab to clean the bore (Note: Do not use abrasives or tools to clean the bore: any scratches caused may necessitate replacing the Bendix AD-9si air dryer.) Superficial external corrosion and/or pitting is acceptable.

2.Clean the o-rings with a clean dry cloth. Do not use solvents.

3.Inspect for physical damage to the bore and the check valve seat. If the bore is damaged (by scratches etc. that would prevent the delivery check valve from seating), replace the AD-9si air dryer.

4.Inspect the delivery check valve, o-rings, etc. for wear or damage. Replace, if necessary, using the check valve replacement kit available at any authorized Bendix® parts outlets.

ASSEMBLY

1.Lubricate the smaller o-ring and check valve body with a heavy duty lithium grease.

2.Install the o-ring on the check valve body by sliding the o-ring over the set of four tapered guide lands. The o-ring groove holds the o-ring in its correct location.

3.At the other end of the check valve body, the spring is installed over the set of four straight guide lands. When the spring has been pushed to the correct location, the check valve body is designed to hold the end of the spring in position: be sure that the spring is not loose before continuing with this installation.

4.Install the assembled check valve body/o-ring/spring in the delivery port so that the o-ring rests on its seat and the free end of the spring is visible.

5.Grease the larger o-ring and install it onto the cover.

6.Replace the delivery check valve cover and torque to

720–840 in-lbs.

7.Before placing the vehicle back into service, check to see that the system pressure now builds to full operational pressure.