3629205 Is A Coolant Thermostat For Cummins Heavy-duty Diesel Engine, An Original Factory Part, Commonly Used in Models Such As NT855/K19/K38/K50

3629205 is a coolant thermostat for Cummins heavy-duty diesel engines (85℃/185°F), an original factory part, commonly used in models such as NT855/K19/K38/K50, etc. It controls the large circulation of the cooling system and stabilizes the working water temperature.

I. Basic Information
Part Number: 3629205 (also marked as 3629205-20)
Type: Wax-type thermostat (coolant / water thermostat)
Opening Temperature: 85℃ (185°F); Fully Open at approximately 95℃
Brand: Cummins Original (Chongqing Cummins / Chongkang)
Applicable Models: NT855, N14, K19, K38, K50, VTA28, etc. of heavy-duty diesel engines
Application Scenarios: Generator sets, mining machinery, ships, construction machinery, oilfield equipment.

II. Technical Specifications
Dimensions: Diameter approximately 70 mm, Height approximately 75 mm
Material: Brass shell, stainless steel spring, high-quality temperature-sensitive wax core
Working Temperature: -40℃ to +120℃
Sealing: Temperature-resistant and aging-resistant rubber sealing ring
Weight: Approximately 0.22 kg

III. Core Functions
Temperature Control: Closed below 85℃, coolant flows in a small circulation (only within the engine, not through the water tank), rapid warm-up; reaches 85℃ and starts to open, 95℃ fully open, coolant flows in a large circulation (through the water tank for cooling), preventing high temperatures.
Stable Water Temperature: Controls the working temperature within 85–95℃, avoiding undercooling / overheating, improving combustion efficiency, reducing wear, and lowering fuel consumption.
Protecting the Engine: Prevents low-temperature wear, engine oil dilution, carbon deposits; avoids high-temperature cylinder pulling, bearing warping.

IV. Interchangeable Models
Cummins: 3017360, 3629205CQ
Freigaga / Others: No fully universal model. It is recommended to use original factory parts.

V. Installation and Replacement Tips
Location: Installed in the water outlet of the cylinder head / thermostat seat, pay attention to the installation direction (copper head towards the engine, flange facing outward).
Replacement Cycle: Every 2000–3000 hours or 2 years (whichever comes first); Check and replace immediately if water temperature is unstable, warm-up is slow, high temperature alarm occurs.
Installation Attention: Clean the seat surface, replace with a new sealing ring; Apply uniform tightening force to avoid leakage; Drain air from the cooling system after replacement.

VI. Common Faults
Always Open: Low water temperature, slow warm-up, high fuel consumption, engine oil dilution.
Always Closed: High water temperature, boiling, power loss, prone to cylinder pulling.
Leakage: Aging of the sealing ring or improper installation.

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