[erik2282]

I'll be working on my truck this weekend changing valve covers and an o2 sensor. I have this annoying whistling noise coming from somewhere in the engine area. What can I check? or what is most likely the issue? Also is this common on these trucks. It has 200,00 miles. I changed t-belt at about 140K miles.
thank you

 

[LGL002]

Check vacuum lines/hoses for the noise. Cracks in those lines can leak and make those sounds. Items like power brake boosters are most often where the leak is.