I have a 4 cylinder 96? T100 and recently I've noticed a moaning sound coming from the engine.

It seems to follow the rpms, but the noise is delayed or lags behind the rpms.

It only happens sometimes when I drive around. When it occurs, I can produce it in gear or in neutral.

It's a moan that sounds like those big rig trucks when they accelerate through their gears, a wooaaaannn type of sound.

Is this an aspiration issue or a sensor going bad? How else can I better describe the problem?

Thank you very much !!!

 

Sounds like it might be your radiator fan - factory fans have a clutch built in, it mooaaans when you first start, then dies after a few minutes - and when engine heats up enough, moans & lags behind your RPMs a bit - so it comes & goes. The idea is the clutch tightens up to spin the fan when it gets hot enough to need it, freewheels if it's not needed, saving a bit of engine power & fuel. When they're still quite cold, they tighten enough to make the noise.

Just a guess - but see if that seems to fit when you're getting the sounds.

 

tstockma -

I think you are dead on. This sounds to be exactly what it is.

I'll get my friend to rev the engine when it does it next and put an ear next to the radiator fan.

Thanks big!

 

YW - it does take some getting used to. Some people people prefer to replace them with electric fans with a thermo switch, like you might be more used to in modern cars, there's a theoretical boost in economy since they only switch on when truly needed, and even when free-wheeling, these hydraulic clutch fans drain some energy thru friction.

And I'm guessing the noise is kinda hard to "localize" that howl but your confirmation of those symptoms, make it real likely we've found it. Have fun!