Frequently Asked Questions About Kenworth W900B/W900L Fan Blades & Shrouds

What are the key differences between fan blades for W900B and W900L models?

While W900B and W900L models share many components, their fan blade requirements can differ based on the engine configuration and model year. W900B models (manufactured 1980-1989) typically use 24-inch to 28-inch fan blades with specific bolt patterns for Caterpillar 3406B engines. W900L models (1989-present) often require different mounting configurations, especially for newer emissions-compliant engines. Always verify your engine model and serial number before ordering, as the same truck model year can have different engine options requiring different fan specifications.

How do I determine the correct fan shroud size and mounting style for my truck?

Fan shroud selection depends on three critical measurements: radiator core size, fan blade diameter, and engine-to-radiator spacing. Most W900B/L models use either a two-piece or three-piece shroud design. Measure from the radiator mounting brackets to determine width (typically 34", 38", or 42"), and check your fan blade clearance - you need 1-2 inches between the blade tips and shroud opening. Steel shrouds are standard, but fiberglass options are available for weight savings. Check for cracked mounting tabs or warped edges on your existing shroud to ensure proper fitment of replacement parts.

What are the most common installation challenges when replacing fan blades and shrouds?

The primary installation challenges include aligning the fan clutch with the water pump hub, ensuring proper blade pitch for your cooling requirements, and achieving correct shroud-to-blade clearance. Many installers struggle with seized fan clutch bolts - use penetrating oil and proper hub pullers to avoid damage. Shroud installation often requires removing the upper radiator hose and sometimes the CAC pipes on newer models. Plan for 2-4 hours of labor, and always check fan tracking with the engine running to prevent blade contact with the shroud.

Which fan blade materials and styles work best for different driving conditions?

Nylon composite fan blades are ideal for most over-the-road applications, offering quieter operation and better fuel efficiency. Steel blades provide maximum durability for severe-duty applications like logging or heavy haul but create more noise and parasitic drag. Blade count affects cooling efficiency - 9-blade fans move more air but consume more horsepower, while 7-blade designs balance cooling with fuel economy. For hot climate operation or frequent mountain grades, consider upgrading to a larger diameter fan or temperature-controlled viscous clutch system.

How can I troubleshoot cooling issues related to fan blades and shrouds?

Start by checking fan blade condition - look for cracks, bent blades, or uneven wear that causes vibration. Ensure the shroud seals properly around the radiator with no gaps allowing air bypass. Verify your fan clutch engagement by checking if it locks up when cold and freewheels when warm. Missing or damaged shroud seals are a common cause of overheating at low speeds. If your fan constantly runs at full speed, the clutch may be stuck engaged, reducing fuel economy. For trucks with aftermarket engines, confirm the fan rotation direction matches your water pump - reversed fans provide minimal cooling.