Fan Clutch Installation

Having disassembled, inspected and repaired the fan clutch in a prior post, we install the clutch to the water pump (of which we discussed interchanges).

Torquing fan clutch to water pump bolts. Note use of aluminum tubing to stop rotation of fan assembly during torquing.

We were unable to easily locate the torque specifications for the fasteners. We referred to Alma Bolt Company & Prime Fasteners’ torque specifications for Grade 5 and Grade 8 bolts. Being that the fasteners on our powerplant were socket head (allen bolt), this is generally an indication of a Grade 8 fastener. According to Alma Bolt’s chart, a 3/8″ Grade 8 has a specified torque of 44 ft. lbs. for a plain bolt, and 33 ft. lbs. for a plated (or wet) bolt.

We set our torque wrench to 32 ft. lbs. and after applying Red Loctite to each fastener, evenly tightened down the fan clutch. After subsequent review, we note that TM 9-2320-280-20-2 specifies 45 lb-ft (page 3-135 Change 3 at c.1.). This is within the specifications provided in the Alma Bolt chart, as the TM does not specify use of loctite which lubricates the thread causing a lower torque reading to equal the same “tightness” as a higher torque with dry threads.

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