For a while now I have a whistling noise from the front of the engine. Very noticeable. Pitch changes with engine RPM. Thought it might be a vacuum hose - checked that and can find no bad or unhooked ones. Sound appears to be coming from under the alternator and A/C compressor area. Had the dealer change a bad plenum gasket at 99k miles - the truck now has 127k on it. There appears to be no oil leakage from anywhere on the engine. I do have pinging on the highway, and lose about 3/4 quart of oil in 3k miles (change it every 3k with Mobil 1). Does this sound like a bad plenum gasket again??
Anyone know about how much it would cost me to have a shop take this thing apart and replace it with an APS plenum kit if I supply the kit?
There used to be a thread here with pics and such on how to R&R the plenum gasket. I can only find a diy sticky with the links to hughes and aps on here now? Don't know if I want to attempt changing it myself - don't know how to "depressurize" the fuel rails to take that stuff apart and such.

 

Make sure your air cleaner is all the way on, and there are no cracks in it. Also, check the back of the cleaner to make sure the tabs are there still. They break off and the only way I've found to keep it closed is with cable ties.

 

It's not the air cleaner. Does it with it completely off or on. Doesn't matter. And I know what you mean on the broken tabs. I have a large hose clamp around one side of mine....

 

Does it stop once the truck warms up?

Ok, now I remember you! You wrote that diy on the steering box I think. Welcome back!

I wrote up a FAQ in the FAQ section that includes a parts list and an explanation to the plenum gasket. As for replacing it, I will be working on a new DIY this spring. The one in the DIY section is very old and the pictures have expired. From the reading in my Haynes and Factory manuals, the plenum repair looks pretty easy. I even think the APS kit comes with instructions.

Depressurizing the fuel rail: Take the cap off. Put a towel around the area of the shrader valve. Stick a small screwdriver in the valve and let the system depressurize (like you would do for a tire). Clean up the spilled fuel.

 

i have the same exact problem...i thought it ws my water pump, but its brand new. and has no play.

i just replaced ALL my vac. lines so i know its not that.

im thinkin idler pulley. is that where is comming from for you?

 

I'm gonna make a video this weekend, to show this, and have an explanation.

 

Bearings going bad in the alt.

 

in my case its not the alt. being a mechanic ive learned tricks on how to listen if the bearings are bad. and they arent...

but for the OP maybe

 

maybe radiator cap blowing off steam ?

 

Yeah - it's me again. I wrote up several "sticky DIY'S" but it seems they are all gone now... I have been working mega hours at work and am an addict on a Nova forum - so I haven't been on here much.
Doesn't matter if warm or cold.
Thanks on the fuel rail explanation! I think I can do the thing myself - just gotta get some warmer weather as my truck won't fit all the way in the garage and still have room to work on it.

Replaced water pump a while back. Sprayed lubricant on idler pulley. No difference.

If it were the bearings in the alt - it would have seized up by now. I've had this for quite a while. It isn't the radiator either. More of a "sucking, whistling sound". 99.9% sure it is an air leak. Just kinda blows my mind how and where I could have an air leak from in that location and not have an oil leak???