As stated in the title, it sounds like I have a pressure air or vaccum leak on my '06 5.9 CTD. The sound appears to come from the driver's side. Is there a valve, hose, or filter that may be dry rotted causing a leak like that or something? I haven't noticed a lack of power, but the sound worries me. Any ideas? Thanks, Shima

 

Check the clamps on the air to air tubing boots and make sure they are tight. Also look for tears in them. I am betting a loose clamp.

 

I bet the noise is coming from the power steering / power brake fluid lines.

 

Does it change when you step on the brakes?

If it does, its a bad hose on the hydro boost pump. replace them to cure the issue.

 

^^^what he said...I had a hissing noise from the area you re talking about...it was one of the hoses from the hydro boost.

 

No change when I put the brakes on. It seems to only be when I have my foot on the accelerator pedal. I hear it most at around 1500 RPMs when the engine isnt running as loud. And as I said, when I take my foot off the pedal, the noise goes away. Thanks for the inputs.

 

An update on my noise. It sounded like a ticking as a leak would sound and I found it was a loose clamp on the #4 fuel injector line. It was vibrating in the loose clamp. Once I tightened the clamp, the ticking sound went away. who would've thunk it?

 

Common problem.

 

Good catch, it is a common problem and normally isn't noticed until the line ruptures.

 

Glad you found it before it ruptured and left you stranded somewhere! I check all those clamps every oil change.