Fan knock

[Bob Sacchi]

Driving the other day I noticed a knock when advancing the spark, so before going on to more complicated things I thought I’d check the easy stuff, and the first thing was the fan.

Good news is the knock disappeared after taking it off, so after inspecting the fan pulley I noticed a slight bit of endplay. It’s one of those newer replacements that was available about 10 years ago when I put it in. The lower pulley is pretty loose, but since the knock was gone after I took the fan assembly out, I assumed that wasn’t where it was coming from.

The arrow shows where the endplay is happening. The arm is on as tight as it will go.




Are these things somehow adjustable or repairable, or is it time to replace it?

[TXGOAT2]

The bushing is probably worn. You might fix it with a washer, but a new one would be a better choice. It's possible the knock is the crankshaft pulley if it is the least bit loose on the shaft. It will get looser, probably sooner than later. Excess wear in any of the parts, including the fan mount, can cause noise.

[ThreePedalTapDancer]

It might be a loose lower fan belt pulley knocking/rocking which stopped when you removed the belt. Check that while you are it to rule it out.

[Jerry VanOoteghem]

Your fan hub is the ball bearing style. They're usually trouble free. The crankshaft pulley however is notorious for knocking when they're loose. Without the load of the fan and fan belt on it, the crank pulley would be somewhat expected to quiet down.

[Norman Kling]

When picking up speed, the fan will pull the pulley forward, and when slowing down it will move backward. This will cause no trouble UNTIL it gets so loose the fan hits the radiatorl Then very expensive to fix. So leave the fan off until it is repaired. Another thing which causes noises if the pin through the lower pulley. Sometimes it gets loose and at idle or slow speed will move from one end to the other. This can be fixed by bending it slightly in the center where it goes through the crankshaft. And if you have the original type crankshaft pulley, they do tend to get loose. Sometimes can be shimmed, best replaced.
Norm

[Humblej]

I second your crankshaft pulley is what is making the noise.

[Jerry VanOoteghem]

Why do you have lock washers stacked up between the hub and the fan blade?

[Dennis Prince]

I put a copper washer in as a spacer many years ago and no problem since.

[Bob Sacchi]

Thanks for the replies everyone. Crankshaft pully was as loose as a goose so off it came.

I looked through my pile o junk and I found a replacement split pulley. I must have bought one years ago and forgot about it. I still have the roll pin too but I can’t find the cap screw. Anyone know the specs on it so I can get another?

Edit: I found the screw too. Must be my lucky day

[Bob Sacchi]

Why do you have lock washers stacked up between the hub and the fan blade?

To tell you the truth, I don’t remember why. I did that over 10 years ago and I’m only now starting to get back into it. It probably had something to do with the fan sitting flush against the pulley face.

[Bob Sacchi]

Ok, so I got the split pulley on (yes Norm, getting that split pin in was a bit of a trial - I read an old post where you had mentioned that). Finally figured out the tension required and it’s humming just fine. Thanks for all the input guys