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I have a 2002 F150, FX4. It has the 5.4 motor. It has developed a very high pitched whine or high frequency noise in the engine, on the drivers side. When I turn off the engine, I can hear it go down and gone after the engine stops, so I am pretty sure it’s not a bearing, but maybe a vacuum leak. I also have another problem that I think is vacuum related, with the AC on, when the engine is under load, the air flow seems to be moved to the defrost vents. Am I right in thinking it’s a leak in the vacuum system?
thanks in advance, for any suggestions.
because there is no attachment in the posts.
and yes, what you are describing sound exactly like a small vacuum leak.
default setting for the HVAC system is defrost. so when you loose vacuum all air comes out of the defroster vents no matter where the vent selector is set.
Thanks Tom,
I guess I just have to try and blow myself up, and try the brake clean, or starter fluid spray test to find it.
Thank again for confirming my thought!
i could not really tell anything for it.
if the 150 is anything like the 250, there really is not much for vacuum lines.
on my 2000, the leak was in the back of the intake plenum where the lines plugged in. one of the lines was split and would only leak under full throttle when the engine shifted.
i want to say the line came from the intake to the canister on passenger side fender. then a line goes to the throttle body area, one goes to the blend door on the ac/heat box, and one goes into the cab at the ac/heater box.
plus the large line that goes to the brake power booster.
the line inside the cab has a connection rite at the top of floor mat and it can get kicked and disconnected on the 250 also.
Still can’t locate the whine and I don’t have any cheese or crackers to go with it. It is really getting frustrating. I have gone through a couple cans of brake clean trying to localize it. It is a constant whine and when I turn off the motor, it winds down after the motor stops.
i have tried to attach a short clip again, Hope this works.
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