Description

Overview

This quick release valve 1/2in x 3/8in suits heavy trailer spring brake circuits with QR-L inline valves. As a result, it lets air exhaust quickly from the spring brake chambers so park brakes release cleanly. You can mount the valve on a frame or bracket close to the axle group for fast response and easy service access.

Features

• Quick release function for QR-L type trailer spring brake circuits
• Frame or bracket mounting for flexible installation on the chassis
• 1/2in NPT supply port with 3/8in NPT delivery ports for common air line sizes
• Direct replacement pattern for Bendix QR-L inline quick release valves

Specifications and Materials

This valve uses a 1/2in NPT inlet to feed the internal quick release gallery and 3/8in NPT outlets to serve the spring brake chambers. The body suits QR-L style inline mounting and typically installs in the service or park brake line between the relay valve and the chambers. Part number: AB8521P. Sealing and port threads match common heavy trailer air brake installations so you can integrate it into existing pipework with standard fittings. For an overview of quick release valve operation in air brake systems, refer to the Bendix manufacturer technical guide at Bendix quick release valve guide

Compatibility and Fitment

This cross-reference listing means this valve is a suitable replacement for the part numbers and applications shown. Some changes in air line plumbing may be required. 5003393, 800332

Compliance and Safety

In service, this quick release valve 1/2in x 3/8in helps keep reservoir pressure available for brake application while venting exhaust air close to the chambers. Always follow workshop air brake procedures, depressurise the system before removal, and check for leaks with a suitable leak detection fluid after installation. In addition, verify park brake hold and release on level ground before returning the trailer to service.

Trailer Applications

You typically use this valve on heavy trailers, dollies, and semi-trailers that run QR-L inline quick release hardware in the park brake circuit. It suits applications where quick exhaust at the axle group improves release time and reduces line back-pressure. Furthermore, it works well as a service replacement when an existing QR-L inline valve has worn or started to leak.

Cross-reference and Suitability

This part cross-references to or suits the following equivalent part numbers and compatible alternatives:

Use the cross-reference list as a guide, then confirm port sizes, mounting style, and circuit layout on the trailer before final selection.

Why Choose ICS Trailers

ICS Trailers focuses on proven air brake components for heavy trailers, including quick release valve 1/2in x 3/8in replacements for QR-L style circuits. Our team understands spring brake plumbing on local fleets, so you can get practical guidance on fitment and cross-reference selection. Browse Air Brake Parts at ICS Trailers via Air Brake Parts