I have a 94 F150 that has a whistling sound that is loud at start up and then comes and goes after the truck has warmed up. I was told that it could be the PCV valve making this noise. IS this true? Also I have tried checking vaccum lines but I can't seem to distinguish the difference between vaccum lines and heater hoses. How can you tell the difference. Also the noise comes from the rear of the engine. Any advice??

 

Which engine ? Usually whistling noises are indictative of a vacuum & or intake leak . Any problems with the idle speed ? Check the Pcv hose esp where it connects to the intake , If its cracked or broken then you will hear it making a noise .

 

Thanks for the info. Its a 94 302 V8..and how would I replace this hose or pcv valve..it looks complicated compared to my old 81 f100 w/ I-6 300

 

First make sure thats where the noise is coming from . The Pcv Valve is located at the back of the right hand valve cover . It has a short curved rubber hose that attaches to the intake . Wiggle it around when the engine is idling to see if thats where the noise is coming from .

 

My motor has this big aluminum thing on top of it. Someone told me it was a mass air flow??? Anyways there is a tube going into the top of it and it looks like it's bolted on. It sounds as if the sound is coming from that. BTY..how often do you need to change the PCV valve?

 

The big aluminum thing is the intake , It should have two rubber hoses running from the air filter housing ( Black box mounted in the left engine bay area ) to the throttle body / intake . If thats where the noise is coming from check those hoses for cracks , leaks etc . I believe the maintenance specs call for replacing the pcv valve every 60K miles . Check your owners manual , it may be 30K miles for severe use . Your engine does not have A Mass Air Flow Sensor .