Four Seasons 36999 Heavy Duty Thermal Fan Clutch

The Four Seasons 36999 is a heavy duty thermal fan clutch designed to optimize engine cooling system performance while improving fuel economy and reducing noise. This clutch automatically engages and disengages the cooling fan based on engine temperature, providing efficient cooling when needed and reducing parasitic drag when full cooling is not required.

Key Specifications:

• Clutch Type: Heavy Duty Thermal (Type C)
• Maximum Clutch Diameter: 7.2 inches
• Fan Bolt Circle: 3.25 inches (82.6mm)
• Bolt Pattern: 4-hole with 5/16-18 thread
• Distance from Clutch to Mounting Flange: 2.25 inches
• Construction: Raw aluminum housing
• Clutch Design: Non-electronic thermal operation

Performance Features:

• Thermal-responsive operation automatically adjusts fan speed based on underhood temperature
• Heavy duty design turns the fan at 70-90% of shaft speed when engaged for maximum cooling
• Reduces fan speed to 25-35% when disengaged to save power and reduce noise
• Bi-metal thermal spring senses temperature changes and controls engagement
• Allows faster engine warm-up by freewheeling at low temperatures
• Improves fuel economy by reducing unnecessary engine load

Quality and Testing:

• Manufactured by Four Seasons, part of the SMP Temperature Control Division
• Tested, validated and inspected before leaving the factory
• Meets or exceeds OEM specifications
• Compatible with multiple OEM part numbers for broad application coverage

This fan clutch is an essential component of the engine cooling system, mounting to the water pump shaft and controlling when the cooling fan operates at full capacity. The thermal design provides superior performance compared to non-thermal clutches by automatically responding to actual cooling demands rather than running continuously.