FAW J6P Expansion Tank: Deconstructing 20 Critical Parts for Flawless Air-Free Cooling

This is a technical deep-dive into the FAW J6P Expansion Tank assembly (Chapter 38), the “lung” of the cooling system for the FAW Jiefang CA3250P66K2L1T1E 6×4 dump truck. This is not a passive “overflow” bottle; it is an active, “dual-logic” component. It provides “Thermal Expansion Logic” (managing coolant volume) and “Degassing Logic” (removing air), which is essential for protecting the engine.

The “Thermal Expansion Logic” is its primary function. As coolant heats up, it expands in volume. The FAW J6P Expansion Tank provides a “safe-zone” for this hot, expanded coolant, preventing pressure from blowing out seals or cracking the radiator. As the engine cools, it “draws back” this coolant, keeping the system 100% full.

The “Degassing Logic” is its most critical safety function. Air is the #1 enemy of a cooling system. Air bubbles cause “steam pockets” (leading to overheating) and “cavitation” (which erodes the water pump). The FAW J6P Expansion Tank acts as the central “air-trap,” allowing scavenged air bubbles to be separated from the coolant and vented safely.

This guide is a vital resource for chassis technicians and parts specialists. We will deconstruct all 20 components, analyzing the “Core Logic” (the tank and pressure cap), the “Plumbing & Degassing Logic” (the network of hoses and pipes), and the “Mounting & Anti-Chafe Logic” (the brackets, clamps, and zip ties that ensure long-term, vibration-proof integrity).

Core 1: The “Expansion & Pressure” Logic (Components 1, 2)

This group represents the “heart” of the FAW J6P Expansion Tank system. These two parts work together to control the physics of the entire cooling circuit.

1. Component: ‘Expansion tank assy’ (1311020-76A)
This (Comp 2) is the main “Reservoir Logic.” This is the FAW J6P Expansion Tank itself. It is a “flow-through” tank, not a “dead-end” overflow. Coolant and scavenged air are constantly flowing *through* it.

Made from a “heat-stabilized polymer,” its “Thermal Buffer Logic” allows it to safely hold expanding, 90°C+ coolant. Internal “baffles” (not visible) help “separate” the air bubbles from the liquid coolant, allowing the air to rise to the top while the air-free coolant is drawn from the bottom. The “MIN/MAX” lines on its side are a critical daily check for technicians.

2. Component: ‘Pressure cap assy’ (1304010-50A)
This (Comp 1) is the “Boiling Point Logic” and the system’s “Safety Valve.” A modern diesel engine runs *above* the normal 100°C (212°F) boiling point of water. This cap “seals” the system.

Its “Pressurization Logic” (e.g., holding 1.0 bar / 15 PSI) raises the coolant’s boiling point to ~120°C (~250°F), preventing “flash boiling” inside the engine head. This cap is a “dual-action” valve:

Pressure Valve (Out): If pressure exceeds 15 PSI (e.g., from a head gasket leak), a spring-loaded valve opens, venting pressure *out* to prevent the radiator or hoses from bursting.

Vacuum Valve (In): When the engine cools, the coolant contracts, creating a “vacuum.” A second, smaller valve opens to allow air/coolant *in*, preventing the ‘Radiator outlet hose’ (Chapter 37) from “collapsing” under suction.

Core 2: The “Degassing & Plumbing” Logic (Hoses & Pipes)

This group is the “arterial network” that connects the FAW J6P Expansion Tank to the engine and radiator. Its “logic” is to move both “air” and “coolant.”

1. The “Air Scavenger” Logic (Components 7, 8, 15)
This is the “Air-Free Logic” network. It includes ‘Degas hose’ (1311068-61B) (Comp 7), ‘Rear degas hose’ (1311069-61B) (Comp 8), and ‘Degas hose’ (1311036-14B) (Comp 15).

These small-bore hoses connect to the *highest points* of the cooling system (like the top of the ‘Radiator assy’, Chapter 37). Their “Scavenging Logic” is to continuously “bleed” any trapped air bubbles *away* from the engine and *to* the FAW J6P Expansion Tank, where they are safely separated.

2. The “Coolant Return” Logic (Components 5, 12, 19)
This is the “Plumbing Logic.” It includes ‘Rear return water hose’ (1311033-61B) (Comp 5), ‘Return water hose’ (1311033-14B) (Comp 12), and the ‘Rear return water steel pipe assy’ (1311065-14B) (Comp 19).

This network’s “logic” is to take the now “de-aerated” coolant from the bottom of the FAW J6P Expansion Tank and “return” it to the “cold” or “suction” side of the cooling system (e.g., near the water pump). This ensures the water pump only ever receives a 100% solid, air-free “charge” of coolant, preventing “cavitation” damage.

Core 3: The “Mounting & Anti-Chafe” Logic (The SSU)

This group represents the “Smallest Serviceable Units” (SSU) that are essential for the survival of the FAW J6P Expansion Tank in a high-vibration dump truck environment.

1. The “Structural Mount” Logic (Components 11, 18, 20)
This group forms the “Vibration Isolation Logic.” The ‘Expansion tank bracket assy’ (1311040-61C) (Comp 11), ‘Bracket assy’ (1311070-14B) (Comp 18), and ‘Bracket assy’ (1311075-14B) (Comp 20) create a rigid “steel cage.” This “cage” bolts to the chassis frame and securely holds the “polymer” FAW J6P Expansion Tank (Comp 2), isolating it from the worst of the chassis “flex” and engine vibration.

2. The “Sealing” Logic (Components 4, 6, 13)
This is the “Leak-Proof Logic.” The ‘Banjo-type hose clamp B model’ (CQ67640B, CQ67622B) (Comp 4, 6) and ‘Hose clamp’ (1311077-61B) (Comp 13) are the most critical SSUs.

The “Banjo-type” (T-Bolt) clamps provide 360-degree, high-torque “clamping force” on the main hoses. A “worm-gear” clamp would loosen under vibration. A failure of a single clamp (e.g., Comp 6) means a “catastrophic coolant loss” and engine seizure.

3. The “Anti-Chafe” Logic (Components 9, 14, 17)
This is the “Routing Protection Logic.” This group includes ‘Dual pipe clamp assy’ (1311060-61B) (Comp 9), ‘Plastic zip tie’ (T67420376) (Comp 14), and ‘Single pipe clamp’ (1311071A377) (Comp 17).

The “logic” of these parts is to “anchor” the flexible degas hoses (Comp 7, 8, 15). The #1 killer of hoses is “chafing” (rubbing against a sharp metal bracket or hot engine part). The six ‘Plastic zip ties’ (Comp 14) are not a “fix”; they are “Deliberate Engineering Logic” to secure these lines, ensuring they never rub or vibrate, guaranteeing the integrity of the FAW J6P Expansion Tank‘s plumbing.

4. The “Fastener” Logic (Components 3, 10, 16)
The ‘Combination bolt’ (CQ1460825) is the “Hardware Logic.” These 11 bolts (5 + 4 + 2) are used to “secure” the brackets (Comp 11, 18, 20) to the truck’s chassis, completing the mounting system.

FAW J6P Expansion Tank Parts List

The following table provides the complete, detailed breakdown of all 20 component types in the FAW J6P Expansion Tank assembly (Chapter 38) for the FAW Jiefang CA3250P66K2L1T1E 6×4 dump truck.

Core Specifications

The specifications for the FAW J6P Expansion Tank system are defined by its dual function of managing coolant volume and actively degassing the engine.