Patrol 65 wrote:
Having owned an 84 Sportscoach with a 454 cid, I would bet the fan clutch is the problem. Mine was so loud when it engaged that it sounded like the transmission was slipping causing the engine to race. It would come on often and with the loud noise, it couldn't be missed. These engines use a viscous fluid type fan clutch which fails as they age. I would be concerned because you stated that it doesn't engage above idle when it should.
+1 ,Exactly how my coach fan operates. definitely Know when fan engages.