- Fan operation can be checked by spinning the fan by hand.
- A noticeable wobble or any blade that is not in the same plane as the rest indicates that replacement is in order. The fan can also be checked by removing it and laying it on a flat surface. If it is straight, all the blades should touch the surface. Never attempt to straighten a damaged cooling fan. Bending it back into shape might seem easier (and cheaper) than replacing it, but doing so is risky. Whenever metal is bent, it is weakened.
- Fan clutches use a fluid-filled chamber (usually silicone) to turn the fan. Obviously, loss of the drive fluid will render the fan useless.
- One of the simplest checks is to visually inspect the fan clutch for signs of fluid loss.
- Oily streaks radiating outward from the hub shaft mean fluid has leaked out past the bearing seal.
- Most fan clutches offer a slight amount of resistance if turned by hand when the engine is cold. They offer drag when the engine is hot. If the fan freewheels easily hot or cold, replace the clutch.
- Another check that should be made is to push the tip of a fan blade in and out. Any visible looseness in the shaft bearing means the fan clutch should be replaced.
- Fan blades are balanced at the time of manufacture but can be bent if handled carelessly.
- Likewise, fan clutches are machined very accurately to run true. However, rough handling at the time of pump replacement causes nicks and dents on the mounting faces. This can cause the fan blade to be installed crookedly. Serious trouble might follow soon after the car is back in service.
- Therefore, handle fan clutches and blades with care and be sure to file away any nicks, burrs, or dents someone else might have caused. Obviously, if any fins have been broken off the fan clutch, it must be replaced.
Damaged fan shrouds can usually be repaired if the damage is not severe. Polyethylene and polypropylene plastics can be hot-air or airless welded. Fiberglass can be glued with epoxy. The important rule here is never leave a fan shroud off. The shroud is needed to help the fan work at peak efficiency and leaving it off will affect the fan's efficiency.