I have a 2008 Ford F-250 super duty put new fan clutch in and it won't Engadge
They freewheel to allow the engine to turn without resistance, they warm up and engage based on higher ambient temps, higher engine temps, and airflowing thru the radiator, you can notice their sound change during extended idle periods. they increase noticeably in stages to couple up to their impeller within. if they freewheel under those conditions, they have failed, if they leak silicone fluid, they have failed, if you can feel roughness in them or wiggle them in and out and feel them rock over center they are failing. leaving them lying down is not recommended when they were installed but you are servicing parts on front of the engine. if you take the propeller off, leave it standing against something. If years of operation pass, they lose some rpm capability each year, measurably, till they constantly freewheel hot, and or can catch and cause a roaring condition. OEM parts are the best and last.
This means, to test yours by operation, you would listen to it run, park it where conditions are warmest, leave it for extended idle, and wait, busy yourself, listen, soon you should notice a change in the sound and even a second stage after further increase in temperatures. there would be some resistance noted trying to turn a new one. by hand
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