Fan noise? 4.0 98 ranger

[redtruck]

I have a 98 Ranger 4.0 with 84,000. On hot summer days, when the engine is warm I will get a loud humming type noise. The motor never comes even close to overheating, the temp guage stays dead center of normal. The cooling fan is always running, so I don't think it has anything to do with that. The a/c on or off, it still makes the same noise. I did a little looking around online could the idle air control valve be causeing this noise? It is a loud kind of annoying noise but does not seem to hurt anything.

 

[Explorin94]

Does it stay at that constant hum all the time? With the engine off try and move the cooling fan with your hand. See if it is easy to move or tough. If it is tough your clutch for the fan is bad. Another thing to do is take the fan off , if you can. This takes a special tool for removal. If you can get it off, take it off and then start it up to see if the noise went away.

 

[shadetree]

IAC hum is fairly common, not only on Ford vehicles, but others as well. It doesn't cost anything to clean it other than a can of cleaner. I would do that first, then see if it goes away. shady

 

[Wicked_Sludge]

he says it only happens on hot days...so his fan clutch is probably working just fine. if it was locked up, it would make the noise all the time.

your fan is spinning all the time, but its speed changes depending on how much airflow your engine needs. its normal for it to be louder (much louder) on hot days at low speeds.

provided thats what your hearing

 

[redtruck]

Everything with the fan seems ok. It only seems to do this on hot days, when the temp is in the 90's or higher. It almost sounds like something additional is coming on, by that I mean it is not a "normal" noise that just gets louder. But a whole new noise entirely. Other then sounding really odd, and being annoying it does not seem to harm anything. All the guages stay in the normal, no warning lights come on. I am going to let it idle in the driveway a while and see if it will do it while it is cooler. Thanks to all who have read and replied.

 

[plainsranger]

does the noise change pitch or go away all together when you rev it up?

 

[redtruck]

no, does not change pitch or go away when you rev engine. It just will eventually stop after driving down the road, then come back when sitting at a red light, or driving at a slow speed for a while.

 

[Wicked_Sludge]

i dont think you have a problem. what your describing is perfectly normal fan clutch operation.

 

[plainsranger]

my guess is that he has the airbox vibration that is causing the hum

 

[redtruck]

I let it idle in the driveway today and it eventually made the noise. Humm actually is not the best description, fog horn is more like it. The temp outside today here is 60. Thanks for all that have replied I really do appreciate it!

 

[Wicked_Sludge]

do you have a video camera? i think a video of it making this noise is the only way we'll ever know for sure what it is.

 

[redtruck]

I'll see if I can borrow a video camera.