FAW J6P Thermostat & Water Pump: 30 Essential Parts for Flawless Thermal Control

Welcome to this expert deconstruction of the FAW J6P Thermostat and Water Pump assembly (Chapter 27). This is the complete “Thermal Management” module for the FAW Jiefang CA3250P66K2L1T1E 6×4 dump truck.

This is a complex “Logic Assembly” of 30 component types, engineered to perform one task: to maintain the engine’s perfect operating temperature (90-100°C) under all load conditions, from a cold start to a heavy uphill pull.

The “Dual-Circuit Logic” is the key to this FAW J6P Thermostat system. When the engine is cold, the ‘Wax-type thermostat assy’ (Comp 3) is *closed*. This “Bypass Logic” forces coolant to *bypass* the main radiator and circulate only within the engine block, allowing the engine to warm up rapidly. This reduces wear, improves emissions, and provides faster cab heat. Once the coolant reaches operating temperature (e.g., 85°C), the ‘Thermostat’ opens, “closing” the bypass and “opening” the main circuit, forcing 100% of the coolant to the radiator. This entire process is powered by the ‘Water pump assy’ (Comp 26), the “heart” of the system.

This expert guide is an essential resource for engine technicians, fleet managers, and parts specialists. We will deconstruct the entire 30-component group into its four primary “logic” systems: the “Thermal Regulation Logic” (the FAW J6P Thermostat and its housing), the “Fluid Circulation Logic” (the water pump and inlet pipes), the “Coolant Conditioning Logic” (the water filter and shut-off valves), and the critical “Sealing & Plumbing Logic” (all the gaskets, pipes, and O-rings) that connect the FAW J6P Thermostat system.

Core 1: The “Thermal Regulation” Logic (The FAW J6P Thermostat)

This group is the “brain” of the entire cooling system. Its logic is to intelligently direct the flow of coolant based on temperature.

1. Component: ‘Wax-type thermostat assy’ (1306010-29D)
This (Comp 3) is the core of the FAW J6P Thermostat assembly. The list calls for two (2) of them. This “Dual-Thermostat Logic” is a high-performance, fail-safe design. It provides a massive “flow-through” capacity (essential for a heavy-duty engine) and provides redundancy. If one thermostat fails in the “closed” position, the other can still provide enough flow to prevent an immediate, catastrophic overheat.

The “Wax Motor Logic” is how it works. This is a non-electric, self-contained unit. A small, brass “pellet” inside is filled with a special wax that is engineered to melt and expand at a precise temperature (e.g., 85°C). As this wax expands, it pushes a small piston, which overcomes a spring and opens the main valve. This is the “logic” that opens the path to the radiator. As the engine cools, the wax solidifies, and the spring forces the valve shut.

2. Components: ‘Thermostat body’ (1306021-863) & ‘Thermostat cover’ (1306013-70A)
This (Comp 5 & 2) is the “Housing Logic.” The ‘Body’ is the main cast-iron or aluminum manifold that bolts to the engine. It contains the “bypass” port. The two ‘Thermostats’ (Comp 3) sit inside this body. The ‘Cover’ (Comp 2) is the “cap” that bolts to the body, and it contains the main “outlet” port that leads to the radiator. The ‘Gasket-thermostat’ (Comp 4), of which there are two (2), provides the critical “static seal” that prevents coolant from leaking *around* the closed thermostat, which would defeat the “fast warm-up” logic. The entire FAW J6P Thermostat housing is a critical, high-flow junction.

Core 2: The “Fluid Circulation” Logic (The Water Pump)

This group represents the “heart” of the cooling system. While the FAW J6P Thermostat is the “brain,” this component is the “muscle.”

1. Component: ‘Water pump assy’ (1307010-36D)
This (Comp 26) is the “Centrifugal Flow Logic.” This is a belt-driven (from the FEAD system) pump. Its “logic” is to be a high-volume, relatively low-pressure pump. An internal, multi-bladed “impeller” spins at high speed. It doesn’t “suck” water in; it “slings” it outwards by centrifugal force, creating a low-pressure void at its center (the “inlet”) that draws coolant in, and a high-pressure zone at its edge (the “outlet”) that pushes coolant into the engine block.

The “Mechanical Seal Logic” is its most critical feature. The pump shaft (which holds the pulley on the outside and the impeller on the inside) must pass *through* the pump housing. A “mechanical seal” (a spring-loaded, carbon-and-ceramic ring) is what prevents high-pressure coolant from leaking out. This seal is “water-lubricated.” When this seal eventually wears out, coolant will drip from a “weep hole” in the bottom of the pump casting. This “Weep Logic” is a built-in “failsafe indicator,” telling the technician the pump must be replaced before the bearing fails completely.

2. Component: ‘Water pump inlet pipe assy’ (1307050-29D)
This (Comp 14) is the “Main Suction Logic.” This is the large-diameter pipe that connects the ‘Water pump assy’ (Comp 26) to the “outlet” (bottom) of the radiator, completing the main cooling circuit. It’s a critical-flow component, securely bolted on (Comp 15) to prevent any air from being sucked into the system.

Core 3: The “Coolant Conditioning & Service” Logic

This group’s “logic” is to “filter” and “chemically treat” the coolant, a feature unique to heavy-duty systems and vital for protecting the FAW J6P Thermostat and engine.

1. Component: ‘Water filter assy’ (1307020-29D)
This (Comp 17) is the “Conditioning Logic.” This is not just a particle filter. Its “logic” is to be a “Bypass Filter” that contains “Supplemental Coolant Additives” (SCAs). A small “bleed” of coolant constantly flows through this filter.

The “SCA Logic” is to slowly release chemicals (like nitrites and molybdates) into the coolant. These chemicals are essential. They “plate” the inside of the “wet” cylinder liners, preventing “cavitation”—a process where tiny, imploding steam bubbles (caused by diesel vibration) act like microscopic jackhammers, eating holes *through* the cylinder liners. This filter’s “logic” is to *prevent* this, making it a critical component for a long engine life.

2. Component: ‘Water filter shut-off valve’ (1307017-29D)
This (Comp 24) is the “Serviceability Logic.” The ‘Water filter’ (Comp 17) is a regular service item. This “shut-off valve” (a ball or gate valve) is installed *before* the filter. Its “logic” is to allow a technician to *stop* the flow of coolant *to the filter*, allowing it to be spun off and replaced *without* draining the entire 30-40L cooling system. This is a massive time- and cost-saving feature.

3. Component: ‘Heater water drain switch assy’ (1311060-50A)
This (Comp 6) is another “Service Logic.” It is a small drain valve located in the “heater core” circuit (the plumbing that provides heat to the truck’s cab). Its “logic” is to allow a technician to drain just the heater core circuit for service, or to help bleed air from that circuit.

Core 4: The “Plumbing & Sealing” Logic (All Others)

This final group’s “logic” is to connect all the components of the FAW J6P Thermostat and water pump system with a 100% leak-proof, high-temperature seal.

1. The “Bypass Pipe” Logic (Component 9)
The ‘Water pump bypass pipe’ (Comp 9) is the “Cold Engine Circuit.” When the FAW J6P Thermostat (Comp 3) is *closed*, this is the pipe that re-routes the “hot” coolant from the engine block *directly* back to the “suction” side of the ‘Water pump’ (Comp 26). This “Bypass Logic” is what allows the coolant to circulate (and the cab heater to work) *before* the engine is at operating temperature.

2. The “Interface” Logic (Components 18, 20)
The ‘Intermediate connecting pipe’ (Comp 18) and ‘Single-pipe intermediate connecting pipe’ (Comp 20) are the “Interface Logic” components. These are rigid, pre-formed pipes that connect the ‘Thermostat body’ (Comp 5) to the cylinder head or other parts of the block. They are used in tight spaces where a flexible rubber hose would kink, melt, or rub through.

3. The “Sealing” Logic (Gaskets & O-Rings)
This system uses three types of seals. The ‘Gaskets’ (Comp 4, 8) are “Static Seals” for flat, non-moving surfaces (like the FAW J6P Thermostat cover). The ‘O-rings’ (Comp 10, 19, 25) are “Dynamic Seals” used to seal the ends of the slip-fit “intermediate pipes” (Comp 9, 18, 20), allowing them to expand and contract with heat. Finally, the ‘Copper gaskets’ (Comp 12) are “Crush Washers” for the ‘Hollow bolts’ (Comp 13), creating a high-pressure, metal-on-metal seal.

FAW J6P Thermostat & Water Pump Parts List

The following table provides the complete, detailed breakdown of all 30 component types in the FAW J6P Thermostat and Water Pump assembly for the FAW Jiefang CA3250P66K2L1T1E 6×4 dump truck.

Core Specifications

The specifications for the FAW J6P Thermostat and Water Pump assembly are defined by its function as the complete thermal management system for the engine.