Product Introduction

• Structure: A wax-element type thermostat with a precision-machined metal housing and a rubber sealing ring. It features a temperature-sensitive wax pellet that expands to open a valve, allowing coolant to flow through the radiator.

• Performance: Opens at a calibrated temperature (typically around 82°C) to allow coolant circulation, and closes when the engine is cold to speed up warm-up. This ensures the engine operates within its optimal temperature range, improving fuel efficiency and reducing wear.

Core Function

1. Temperature Regulation: Controls the flow of coolant between the engine and radiator, maintaining the engine at its ideal operating temperature.

2. Fast Warm-Up: Remains closed when the engine is cold, forcing coolant to circulate only within the engine block to reduce warm-up time.

3. Overheat Protection: Opens fully to maximize coolant flow when the engine temperature exceeds the set point, preventing overheating and engine damage.

Thermostat 630-1306004 Yuchai – Precision Engine Temperature Control for Heavy-Duty Performance

Your engine’s cooling system lives or dies by one critical gatekeeper – the thermostat. The Thermostat 630-1306004 Yuchai is a wax-pellet type thermoregulator that senses coolant temperature in real time and modulates flow between the engine block and radiator. When this component performs flawlessly, your Yuchai diesel runs at peak thermal efficiency, burns fuel cleanly, and keeps wear to a minimum. When it fails, overheating, excessive fuel consumption, and premature component degradation follow within hours. METTLEAD Truck Parts delivers this thermostat with OEM-equivalent precision, manufactured under strict quality control and offered at factory-direct pricing that protects your procurement budget.

Key Functions and Business Benefits

What This Thermostat Does for Your Engine

• Rapid Warm-Up Regulation – The wax element begins to expand at approximately 82°C (±2°C), progressively opening the valve to allow coolant circulation toward the radiator. This eliminates cold-start fuel waste and reduces cylinder liner wear during warm-up phases.
• Stable Operating Temperature Maintenance – Once fully open (typically at 95°C), the thermostat sustains a consistent thermal window that optimizes combustion efficiency, NOx control, and lubricating oil viscosity.
• Overcooling Prevention – In cold ambient conditions or during light-load operation, the thermostat restricts flow to the radiator, preventing the engine from running too cool, which causes incomplete combustion and soot accumulation.
• Coolant System Protection – By managing thermal cycling precisely, the thermostat reduces stress on hoses, gaskets, and the water pump seal, extending overall cooling system service life.

Why Procurement Managers Choose This Part

• Cost Efficiency – Factory-direct sourcing from China eliminates distributor markups by 30–45% compared to regional aftermarket channels.
• Reduced Downtime Risk – OEM-spec wax formulation ensures accurate opening temperature, preventing costly roadside failures and unscheduled maintenance events.
• Inventory Consolidation – Compatible across multiple Yuchai YC6 engine variants, simplifying SKU management for fleet operators and parts distributors.
• Verified Fitment – Direct cross-reference to OEM part number 630-1306004 guarantees drop-in replacement without modification.

Technical Specifications

Application Scenario – Yuchai-Powered Heavy-Duty Trucks

The Thermostat 630-1306004 Yuchai is purpose-engineered for the Yuchai YC6 series diesel engines that power a wide range of Chinese heavy-duty commercial vehicles. Much like how the 3698310 connecting rod serves Cummins ISG/QSG/F-series engines by linking piston to crankshaft and converting reciprocating force into rotational power for FOTON Auman heavy trucks, this thermostat acts as the thermal command center for Yuchai-powered platforms. It regulates the critical junction between engine block circulation and radiator cooling across the following vehicle applications:

• DONGFENG Tianlong / Tianjin Series – Long-haul logistics tractors equipped with YC6L280-series engines operating across Southeast Asian and African corridors.
• FOTON Auman EST / GTL – Regional distribution and heavy-haul configurations running Yuchai YC6MK power units.
• SINOTRUK HOWO T-Series – Select Yuchai-configured models for export markets requiring non-Weichai powertrain options.
• JAC Gallop / K-Series – Construction and mining dump trucks utilizing Yuchai YC6A high-torque engines where thermal management is critical under sustained heavy loads.
• Bus and Coach Applications – Yutong, King Long, and Higer coaches powered by Yuchai YC6L/J engines for urban and intercity transit operations.

In every application, the thermostat ensures the engine reaches operating temperature quickly during morning cold starts, sustains that temperature through hours of continuous highway operation, and responds instantly to load changes during urban stop-and-go driving or steep gradient climbing.

OEM/ODM Capability

White-Label and Custom Packaging

METTLEAD Truck Parts understands that distributors and fleet operators often need parts that carry their own brand identity or meet specific market presentation standards. Our manufacturing and packaging capabilities include:

• White-Label Production – Thermostat units shipped with neutral packaging, ready for your brand labels and documentation.
• Custom Packaging – Full custom box design with your company logo, part number cross-reference, installation instructions, and multilingual content for target markets.
• Bulk and Kit Configurations – Available in individual boxes, master cartons of 50/100 units, or bundled with gaskets and O-rings as a thermostat service kit.
• Quality Documentation – Certificate of Conformity, material test reports, and dimensional inspection reports provided per shipment or per batch as required.

Quality Control Process

1. Incoming raw material inspection (wax element melting point verification, brass alloy composition testing)
2. In-process dimensional checks at each machining stage
3. 100% functional testing – every thermostat is validated for opening temperature accuracy in a controlled water bath
4. Seal integrity test under 150 kPa pressure differential
5. Final visual inspection and packaging verification

Customer Case Study – East African Fleet Distributor

A Kenyan truck parts distributor managing aftermarket supply for 1,200+ Yuchai-powered DONGFENG and FOTON trucks across East Africa was experiencing a 12% return rate on thermostats sourced from unverified suppliers. Failed units were opening at incorrect temperatures (some as low as 70°C, others refusing to open until 98°C), causing chronic overheating complaints and warranty claims from fleet operators.

After switching their Thermostat 630-1306004 Yuchai supply to METTLEAD Truck Parts, the distributor received batch-tested units with certified opening temperature documentation. Over 8 months and 3,500 units shipped, their return rate dropped to 0.3% – a 97% reduction. The precise thermal response of each thermostat eliminated overheating incidents and rebuilt trust with their fleet operator clients. Additionally, METTLEAD’s custom packaging with bilingual English/Swahili installation guides reduced installer errors at the workshop level.

“We tested five suppliers for the 630-1306004 thermostat before settling on METTLEAD. Their consistency is unmatched – every single unit opens within spec. Our warranty claims disappeared almost overnight.” – Procurement Director, Nairobi-based parts distributor

Frequently Asked Questions – Thermostat 630-1306004 Yuchai

What symptoms indicate the Thermostat 630-1306004 Yuchai has failed?

A failing thermostat typically presents as engine overheating (stuck closed) or engine running cold with poor fuel economy and heater output (stuck open). If your Yuchai engine takes unusually long to reach operating temperature or climbs above 100°C under normal load, the 630-1306004 thermostat should be inspected immediately. Coolant temperature gauge fluctuations during steady-state driving also indicate a thermostat that is partially stuck or opening erratically.

Can the Thermostat 630-1306004 Yuchai be tested before installation?

Yes. Submerge the thermostat in water and gradually heat it while monitoring with a thermometer. The valve should begin opening at 82°C (±2°C) and reach full lift by 95°C. If it opens early, late, or not at all, the unit is defective. METTLEAD performs this test on 100% of production units before shipment.

What is the recommended replacement interval for the 630-1306004 thermostat?

Under normal operating conditions, the Thermostat 630-1306004 Yuchai should be replaced every 100,000 km or every 2 years, whichever comes first. Trucks operating in extreme heat environments (ambient above 45°C) or using poor-quality coolant should inspect at 60,000 km intervals. Preventive replacement during major service intervals is significantly cheaper than emergency roadside repairs.

Is this thermostat compatible with all Yuchai engine models?

The 630-1306004 is designed for Yuchai YC6L, YC6J, YC6A, and YC6MK series engines. It is not interchangeable with Yuchai YC4-series or YC6G-series engines, which use different thermostat housings and temperature ratings. Always verify the OEM part number against your engine’s parts catalog before ordering.

Does coolant type affect Thermostat 630-1306004 Yuchai lifespan?

Absolutely. Low-quality or incompatible coolant causes corrosion deposits on the wax element and valve seat, leading to sticking or inaccurate opening behavior. Always use an ethylene glycol-based antifreeze meeting Yuchai’s specification (typically equivalent to ASTM D3306 or GB 29743). Mixing coolant types or using plain water accelerates thermostat degradation significantly.

How does the Thermostat 630-1306004 Yuchai differ from universal aftermarket thermostats?

Universal thermostats use generic wax formulations calibrated to approximate opening temperatures. The 630-1306004 uses a Yuchai-specific wax compound tuned precisely to 82°C, matched to the engine’s ECU coolant temperature mapping and fan engagement logic. Installing a universal thermostat with a different opening point can trigger fault codes, degrade emissions performance, and void powertrain warranty coverage.

Ready to Secure Your Supply of Thermostat 630-1306004 Yuchai?

Every day your trucks run with aging or substandard thermostats, you lose fuel efficiency, accelerate engine wear, and risk costly breakdown events. METTLEAD Truck Parts delivers batch-tested, OEM-spec Thermostat 630-1306004 Yuchai units at factory-direct pricing with flexible MOQ and reliable international shipping.

Take the next step:

• Request a quotation with your volume requirements and delivery timeline
• Ask about custom packaging or white-label options for your distribution network
• Inquire about bundle pricing with related Yuchai cooling system components

👉 Contact our team now to get a competitive quote within 24 hours. Our Yuchai parts specialists are ready to support your procurement process from sample validation through bulk shipment.

Browse our complete range of Yuchai engine components – water pumps, coolant hoses, temperature sensors, and more – in our Yuchai Engine Parts catalog.