I have an 04 Ranger 3.0L regular fuel with AC. I have a chirp that will not go away. I've exhausted all options. Ive replaced the alternator, tensioner, idler, harmonic balancer, an put a $40 belt in it. I've used a stethoscope and listened and dont hear and of the pulleys making a chirp. Its driving me crazy can anyone shed some light on what I could be missing?

 

probably the cam synchronizer, put your scope on that and see if that is the noise. If that is it then you better replace it right away because that little guy drives the oil pump

 

this would be my guess as well. I went through the same process with my 03 Mazda 3.0

 

Yup, been there twice with my truck. Buy the Motorcraft one if possible, they're more reliable than the ones from the parts store.

 

Simpler test to start off with is to wait until engine is STONE cold, i.e. sat overnight

Remove fan belt from crank
Start engine, battery light will stay on, no alternator
Listen for any noise, engine bay will be VERY quiet with no fan
If you hear a 'squeak' then yes most likely Cam Synchronizer

If no 'squeak' then shut off the engine and spin pulleys manually one will feel "bad"

You can ONLY run the engine for 2 minutes with NO water pump, 2 minutes is plenty of time to ID a noise