How to test a viscous fan

[Pedro_The_Swift]

This from BorgWarner
was the original a BW unit?

Peter


http://www.fanclutch.com/picsdocs/borgwarner_viscous_fan_drive_test_procedure_(bi-metal_drives_only).pdf

[DiscoKym]

"How do I know if my fan clutch needs to be replaced?"

From daviescraig (http://www.daviescraig.com.au/Fan_Clutches-b-content.aspx)

These are the most common symptoms of a failed fan clutch:

Engine overheating – with engine hot and ignition off, spin fan 1-11/2 revolutions indicates a worn clutch.

Excessive Fan Clutch play – push the tip of the fan blade in and out. Any visible looseness in the clutch shaft means the bearing is worn.

Greasy build up – Oily streaks radiating outward from the hub shaft or fluid leaking at centre of thermostat spring.

Bad bearing - Seized, turns rough or has excessive play (more than 1/4" at fan tip).

Freezing up – If the fan blade cannot be rotated by hand, or if hand rotation causes a harsh rumbling, the fan clutch bearing has failed.

Shaft vibration – The fan clutch is mounted on the water pump between the water pump shaft and the fan. Any vibration can mean a worn bearing in the water pump o fan clutch. Since the fan clutch and water pump have about the same life span, it makes sense to replace both at the same time.

Worn thermal spring - Spring is loose.

Some fan clutches will show no visible indication of a problem yet may still be faulty. The following may also indicate a faulty fan clutch:

Fan spins excessively - Three or more times when hot engine is shut off.

Poor air conditioning - At low speedor excessive high side pressures.

Doesn't engage - Fan speed does not increase or "lock up" when the engine is hot.

Does not disengage - Fan clutch won't slow down when the engine is cold.

Note; The fan clutch should be checked for possible replacement when a replacement water pump is being installed.