Hissing/squeaking when idling

[FlyingFatass]

There's a kind of hissing/squeaking noise coming from my engine whenever I start my truck and have it at idle or when I'm slowing down and downshifting. It's been happening for a while now. I recently replaced the alternator belt, and will probably replace the fan belt soon as well. But the sound isn't like that traditional obnoxious squeaking you get from a bad belt. I'm just having trouble pinpointing where the noise is coming from. Has anyone else had the same problem?

 

[feellnfroggy]

probly a vacuum line, have you used a stethoscope or screwdriver or somehting similar to try and pinpoint it>? Does it sound like its under the valve cover or out in hte open? Could it be alternator bearings? does your voltmeter fluctuate? have you checked your idler and tension pulleys for vibration or wobble?

 

[FlyingFatass]

probly a vacuum line, have you used a stethoscope or screwdriver or somehting similar to try and pinpoint it>? Does it sound like its under the valve cover or out in hte open? Could it be alternator bearings? does your voltmeter fluctuate? have you checked your idler and tension pulleys for vibration or wobble?

It sounds like its out in the open, near the back of the cylinder head where the intake is. Strangely enough, the noise can be heard much better inside of the cab rather than from the engine bay. I't doesn't sound like it would be bad bearings, nor is it coming from the alternator (the voltmeter reads steady). I haven't checked any of the pulleys for vibration, but still, it sounds like its coming from near the back of the engine.

 

[DirtRider031]

I had the same noise coming from the back left side and got underneath the truck and found out i have a blown head gasket. Does it get louder if you put it under some load?

 

[adsm08]

I think someone put one of those fake waste-gates on your truck to mess with you.