FAW Auxiliary Air Tank Assembly: A Critical Analysis of 10 Core Components

Welcome to this critical technical analysis of the FAW Auxiliary Air Tank Assembly (Assembly 543). This is a complete, chassis-mounted, high-pressure air reservoir system for the FAW Jiefang CA4251P66K24T1A3E5 6×4 diesel semi-trailer tractor. This assembly serves as a vital “auxiliary” storage unit for the truck’s complex pneumatic brake and suspension systems.

The FAW Auxiliary Air Tank Assembly is a “logic” system designed to provide redundant or specialized air capacity. While the main air brake module (Assembly 542) provides primary storage, this ‘Dual-chamber air storage tank assembly’ (3513075-91W) offers dedicated air volume for systems like the trailer brakes, parking brakes, or the pneumatic-over-hydraulic clutch, ensuring system integrity.

This in-depth guide is an essential resource for professional chassis technicians and parts specialists. We will deconstruct the entire FAW Auxiliary Air Tank Assembly into its 10 serviceable component types, including the dual-chamber tank, the ‘Drain valve assembly’, the ‘Tank strap assembly’, the chassis-mounted ‘Bracket assembly’, and all the critical high-pressure fittings and fasteners.

Core Component: ‘Dual-Chamber Air Storage Tank’ (3513075-91W)

The heart of the FAW Auxiliary Air Tank Assembly is the ‘Dual-chamber air storage tank assembly’ (3513075-91W). This is a heavy-duty, steel-walled cylinder, but its “dual-chamber” nature is its key “logic.” This is not just one open tank; it has an internal, welded baffle that divides it into two separate, airtight reservoirs.

This “dual-chamber” logic is a critical safety feature of the FAW Auxiliary Air Tank Assembly. It allows this single component to serve two different, isolated brake circuits. For example, one chamber might be dedicated to the trailer’s service brakes, while the other chamber is dedicated to the truck’s spring (parking) brakes.

This ensures that a catastrophic failure in one circuit (like a severed trailer air line) cannot drain the air from the *other* circuit. This redundancy is the core “logic” of a safe, modern air brake system. The FAW Auxiliary Air Tank Assembly is a key part of this redundant design. These tanks are designed to hold air at 120-130 PSI and must be free from external damage or internal rust, which could lead to a catastrophic rupture.

The Mounting System: Bracket (3513075-75A) & Straps (3513085-91W)

A heavy, air-filled tank must be securely mounted to the chassis. The FAW Auxiliary Air Tank Assembly uses a robust, two-part system.

**1. ‘Bracket assembly-auxiliary air tank’ (3513075-75A):** This is the main “shelf” or “cradle.” It is a heavy-duty, fabricated steel bracket that bolts directly to the truck’s main C-channel frame rail. This bracket provides the rigid, structural support for the tank. This component of the FAW Auxiliary Air Tank Assembly is secured to the chassis using ‘Hex flange bolts’ (Q1841440, Q1841475) and ‘Hex head flange lock nuts’ (CQ32614), ensuring a vibration-proof connection.

**2. ‘Tank strap assembly-auxiliary air tank’ (3513085-91W):** The parts list calls for two of these. These are high-tensile steel bands that “strap” the cylindrical tank down into its cradle bracket. These straps are what prevent the tank from shifting or falling off. They are designed to be tensioned with bolts to provide a high-clamping force. This bracket-and-strap “logic” is the standard for safely mounting cylindrical air tanks, and it is a key part of the FAW Auxiliary Air Tank Assembly.

Service “Logic”: Drain Valve (3513100-1500) and Test Port (T833)

The “logic” of the FAW Auxiliary Air Tank Assembly is designed around regular maintenance. The ‘Drain valve assembly’ (3513100-1500) is the most important serviceable component. The list calls for two (one for each chamber of the dual-chamber tank).

Air from the engine’s compressor is hot and contains moisture. As this air cools in the tank, the moisture condenses into liquid water. This water is corrosive and dangerous; it can rust the steel tank from the inside out, and in cold weather, it can freeze, blocking the air lines and causing complete brake failure.

The “logic” of these drain valves is to provide a simple, manual way (usually a pull-cable or a petcock) for the driver to “drain” this accumulated water from the tanks at the end of every day. This daily purge is the single most important PM task for the FAW Auxiliary Air Tank Assembly.

The ‘Quick-connect test connector’ (T833) is a diagnostic “logic” port. It is a one-way, spring-loaded valve that allows a technician to quickly connect a pressure gauge to the FAW Auxiliary Air Tank Assembly to test the system pressure, without having to disconnect a main (and dangerous) high-pressure line.

Fittings and Plumbing: The Grommet System

The FAW Auxiliary Air Tank Assembly must connect to the rest of the truck’s air system. This is done with a series of high-pressure, “push-to-connect” style fittings. These are the “grommets” and their associated seals.

This parts list includes:

• **M22 Fittings:** Four ‘Grommet (M22) with sealing ring assy’ (3513410-1500). These are the large ports, likely for the main supply *in* and the main service brake supply *out*.
• **M16 Fittings:** One ‘Grommet (M16) with sealing ring assy’ (3506410-1500). This is a smaller port, perhaps for a sensor or the parking brake line.
• **Plug:** One ‘Plug chamber (M16) with sealing ring assy’ (3506415-1500), used to seal an unused M16 port.

The “logic” of these fittings is that they are sealed by ‘Special-shaped sealing rings’ (3513403-1500 for M22, 3506403-1500 for M16) and physically locked in place by ‘Circlips’ (3513407-1500 for Φ12, 3506407-1500 for Φ10). A failure of one of these small o-rings or circlips will cause a persistent, hard-to-find air leak, which is a major fault in any FAW Auxiliary Air Tank Assembly.

FAW Auxiliary Air Tank Assembly Parts List

The following table provides the complete, detailed breakdown of all 10 component groups (totaling 29 pieces) identified in the ‘Auxiliary Air Tank Assembly’ (543) diagram for the FAW CA4251P66K24T1A3E5 tractor.

Technical Specifications and Assembly Context

The specifications for the FAW Auxiliary Air Tank Assembly are defined by its function as a high-pressure, dual-circuit air reservoir. The FAW Auxiliary Air Tank Assembly is a critical safety component of the pneumatic brake system.