After driving for a while, I hear a loud whistle coming from the engine of my '85 Econoline. 302 4 bbl. Sounds like it does when they overheat, but this one is not hot. . Temp gauge stays normal, doesn't lose any coolant and when I shut it off, it isn't hot. Could the radiator cap make that noise, but not be losing coolant? Doesn't seem to be hurting anything, but it's driving me crazy.

 

Have you tried to use a piece of hose with one end to your ear to pinpoint where the whistle is originating? I know you know how to do this , did you forget to use this trick?

 

Yep, sure did forget it.

 

Look at it this way, sometimes the ability to forget can be a blessing !

 

Still can not find the source of the noise. Since it runs rough, wondering if it could be an intake manifold leak? It really sounds like the whistle when an engine overheats, but this one is not overheating. The noise is not there until the engine gets warm.

 

Does the engine have an AIR pump on it? Possibly one of the check valves for that system are not sealing completely.