Originally Posted by wmajinw
Guys, what in the gods name is this sound when shutting the engine off? It's driving me insane and I don't know if it's normal or if I should be concerned.
Ok, so it works like this. Starter has a one way sprag clutch. Whenever the engine turns backwards it will engage it and take the starter for a brief spin. Yes, on shutdowns, there will be one cylinder moving up into compression stroke. It can't quite make it and will rebound back causing a slight engine reversal, engaging the starter sprag. Perfectly normal on all starter clutches that are attached to the crank full time. This very brief period of time in reverse rotation will not cause problems with the cam chains as the tensioners are still under residual oil pressure so the chain system is still tight. Turning the engine over otherwise is not recommended in a reverse direction. The higher the mileage or lack of secondary shim amounts, the greater the risk of cam jumping timing due to uncontrolled chain slack.
Oh, once in a while you might not hear the starter sound. This is because the engine just happened to just hump over the compression stroke on that cyl, so no backward rotation has happened.