When I'm at a complete stop and have all accessories turned off there is a loud whining noise coming from the middle of the dash. I'm guessing that it is actually coming from the engine compartment. Has anyone experienced this on their truck? It's a 98 4x4 with the 4.6. Could I have a vaccume leak somewhere and thats what the noise is?? If I put the engine in park is seems to go away but then it comes back when in drive and not moving. When the engine is under load. Any ideas??
If so - The 98 Vacuum lines plug-in is visible and easy to get at under the dash. if you look in the right spot . Sitting in the driving position about 4" above your right ankle to right is a plug-in with 4 or 5 different colored lines. Check that for leaks.
My 97 had pinhole in the lines that run from the engine to just behind the battery. I found them by keeping the engine running and spraying the lined with a squart bottle. When the sound stopped for a second and returned I looked in that area.