Weird whistle

[Red_Diesel]

Lately my truck has had a very high pitch whistle sound when it idles. It is coming from the front were the engine is. what could the problem be? Could it be a blown head gasket?

[bigcountrysg]

I would check the water pump and belt tension pulley.

Other then the normal kind of whistle from a possible boost leak the common place on a 6.0 to develop a weird whistle is the overflow jug cap. If its been over heated or the headgaskets are starting to go and put pressure in the jug it can distort and cause a whistle. Most of the time you can get it to stop by putting a new cap on but that just covers it up till that cap goes bad. Just a possibility.