Magnetic clutch
Cross section of a magnetic fan clutch
1 - primary disk; 2 - hysteresis disk; 3 - secondary disk; 4 - permanent magnet; 5 - steel disk; 6 - ball bearing
1. With the engine stopped, rotate the fan by hand and check that it rotates evenly and silently.
2. Replace the fan clutch if it does not resist rotation or is noisy.
Viscous clutch
Cross section of a viscous fan clutch
1 - clutch housing (secondary part); 2 - drive disk (primary detail); 3 - shaft with flange; 4 - seal; 5 - needle bearing; 6 - cooling fins; 7 - oil scraper; 8 - spring; 9 - persistent finger; 10 - bimetallic plate; 11 - cover with a holder; 12 - intermediate washer; 13 - falling hole; 14 - valve lever; 15 - tank; 16 - working chamber
1. Warm up the engine to normal operating temperature and maintain engine speed between 4000 and 4500 rpm. Do not close the radiator, otherwise the clutch will not respond correctly to temperature changes.
2. Using a thermometer (temperature gauge) make sure that when the engine warms up to 90-95°C, the fan speed increases by about 1000 rpm. With a properly functioning clutch, this will be noticeable by ear. A defective clutch must be replaced.