Truck: 1979 F250 Ranger CS 2WD Reg Cab, From California so it has smog pump, Factory AC, PS.

I just started getting an intermittant rattling noise that appears to originate from the fan/pulley area. I notice that I have a fan clutch that I hadn't noticed prior. (Just got the truck in Sept. from Original Owner.) The noise changes with RPM's but sometimes isn't there at all. I can't find anything loose by hand, It sounds like a bearing go out.

2 Questions: 1) what is the item that the fan is attached to and how does it work? 2) any suggestions on finding the rattles origin?



Top view from Radiator Cap. What is the grey item with fins?

 

The finned device is part of the fan clutch. The clutch lets the fan run slow when temps are low and tightens up to turn it faster as temps increase. It has a bearing inside. With time and miles the bearing goes bad and can get noisy. Usually when that happens you can feel or see a little slop... the fan and/or clutch can move around a little bit relative to the pulley it is bolted to.

The whole assembly, including the pulley, bolts to the water pump which also has a bearing inside that can go bad with time and miles.

If the noise is coming from the fan area, it could be loose bolts or a bad bearing in the fan clutch or water pump.

With the engine off you should be able to turn the fan by hand with light to moderate resitance. That would help find an issue in the clutch bearing. With belt and pulley off, you can turn the water pump by hand to feel for any roughness in its bearing. Those would be my first steps.

 

Thanks Blue & White, The fan spins freely when the motor is not running. And there is a some slight slop in the fan when I go to wiggle it. Not a great deal, but it will wiggle to the touch.

 

In case the fan clutch seems bad, I have had best luck with Hayden brand replacements from NAPA. Not so much with AZ "torq flow" on a later DD. For the water pump, I have had good luck with NAPA brand new replacement pumps... others may be good but NAPA worked for me.

 

I'd just check to ensure that the fan/clutch bolts are tight. If they are and there is still some wiggle I'd say replace the clutch...my guess is you'll be replacing it soon.