weird noise....mechanical fan?

So I'm getting a weird noise. It's sort of rattling/rumbling noise that seems to get faster and slower with engine revs. It was pretty bad this morning so I popped the hood and it sounds like it might be coming from the mechanical fan. Question one, should I be able to turn the blades by hand while the serpentine belt is installed? Question two, the belt needs to be replaced, could this be causing a noise as well?

S

Question one - yes you should be able to, the OEM mechanical fan clutch contains a viscous silicone fluid that thickens when heated so that the fan spins more when the engine is warm.

Question two - maybe but unlikely. The belt would more likely cause a rather painful squealing noise especially when wet or cold.

EDIT: as for the actual source of the sound - have you checked your exhaust system? Other than that, maybe an off-balance crankshaft or some bad bearings?

Thanks! I feel better knowing the fan isn't the issue...

Yeah, the exhaust is a possible cuplrit. I know it needs to be replaced, could the sound come and go if it was an exhaust problem?

It wasn't bad at all when I left the house this morning, and it suddenly got real bad when I got to work, then seemed to die down after that....other weird thing, seem to hear it better sitting inside the vehicle than when outside of it.

S

I'd bet on exhaust then. Though it also could be shot transmission/engine mount bushings - if those are worn through you'll get a lot more engine noise conducted through the frame to the body and will hear it inside the cab. Let it cool down for an hour or so, then fire it back up and before it has a chance to get painfully hot, use your hands to feel along the exhaust system for leaks. You should feel exhaust puffing out wherever there is one; if this doesn't work you can also just wait for a cold day (ha) and watch for steam coming out of strange places.

If it's your engine/tranny mounts, you should be able to see the problem when you inspect them. Just hope it isn't a crankshaft/bearing issue because those get pretty annoying/expensive.

If you haven't already, make sure it's not the fan hitting the fan shroud. It's a pretty common problem and it has these same symptoms. Good luck.

AL BUNDY said:

If you haven't already, make sure it's not the fan hitting the fan shroud. It's a pretty common problem and it has these same symptoms. Good luck.

Click to expand...

X2...I'd be looking at that first. Mine split along the corner, just barely contacting the fan. Couildn't see it unless you moved it.

P.S. BE CAREFUL OF THAT FAN BLADE