Technical Bulletin
Bulletin No: TCH-003-056
Subject:

Initial Release Date: 11-20-2019

Revision Date: 3-9-2024

Page: 1 of 1

BENDIX® PP-1® & PP-8™ PARK CONTROL VALVE WEAR AND REPLACEMENT NOTICE

This bulletin applies to all Bendix® PP-1® and PP-8™ valves in applications where the exhaust port is plumbed
external to the cab. It is mostly applicable to vehicles used in high-park-brake-cycle count applications, like refuse
vehicles or city buses.
When a heavily-worn PP-1 or PP-8 control valve is combined with restrictive exhaust plumbing, the vehicle park
brake force may be reduced. Valve wear may be the result of high-park-brake-cycle count and/or sideloading.
Sideloading can be caused by pushing or pulling the valve button at an angle and not in line with the valve or from
hanging objects from the button.
Bendix® PP-1®
Control Valve

Bendix® PP-8™
Control Valve

Valve
Bottom
View
Example

PP-1
Exhaust Port

Located here for
PP-1 & PP-8 valves

Do not install fittings or tubing into the exhaust port if used for parking brake control. If a worn PP-1 or
PP-8 valve is used for parking brake control and the exhaust plumbing is kinked, bent, or restricted, the
vehicle might not park, and a roll away may result, potentially resulting in injury or death.
DIAGNOSING A LEAKING PP-1 AND PP-8 PARK CONTROL VALVE
When performing any inspection or service, follow the steps below and refer to the guidelines outlined in the PP-1
and PP-8 Service Data sheet SD-03-3611, or instruction sheet as applicable.
1. Run the vehicle until the air system reaches full reservoir pressure (120-135 psi). Turn off the vehicle.
2. Move the control valve button & plunger from side to side and up and down. Do not push the button in. If there
is any play, or if audible leakage is detected, the valve must be replaced.
3. Identify the dash valve exhaust hose location – if there is a hose still connected to the Park Control Valve Exhaust
Port, it is advised to disconnect it and remove any fitting.
4. With the button pulled out (exhaust position), rotate the button and plunger in a clockwise direction – stopping
every 90º to check for leakage.
5. Using a soap solution, check for leaks. The allowable leakage should not exceed a 1” bubble in 5 seconds at
any location on the valve.
6. Push the button in (applied position) and check for leaks. The leakage should not exceed a 1” bubble in 3 seconds
at any location on the valve.
7. Reduce the supply pressure. At a pressure from 60 to 20 psi, depending on the part number specific automatic
release pressure, the button should pop out automatically, exhausting the delivery volume. (This does not apply
to the PP-8 or some PP-1 valves without an automatic release pressure).
For additional assistance, contact the Bendix Tech Team at 1-800-AIR-BRAKE, option 2
(1-800-247-2725, option 2) or techteam@bendix.com.
TCH-003-056 Rev 002 © 2024 Bendix Commercial Vehicle Systems LLC, a member of Knorr-Bremse • 3/24 • All Rights Reserved