My car is making air leaking noise - I think

Car : Mercury Sable 1998

It has some rust holes near the rear wheels. One fine day – it started making noise which is now crossing threshold of ear PAIN.

When the car is on Neutral … there is no noise … but once it crosses speed of 55 miles/ hr … the Noise increases. Beyond the speed of 75 miles/hr … the noise tend to become less.

The noise is coming from somewhere inside the hood… but I am not able to pinpoint the location.

Have you checked for a disconnected vacuum hose?

Thanks for the quick reply.

The noise started after I cleaned the engine … May be I must have disconnected something.

Can you tell me more about disconnected vacuum hose – where to look etc

Thank you again for help.

There tend to be a number of them under the hood, in various places. Just look around carefully for the smallest diameter hoses under the hood (similar in size to the little lines for the windshield washer fluid).

If you do this while the engine is running, the sucking noise from the disconnected hose will probably lead you to the correct area. Just be sure that you are not wearing a neck tie, scarf, loose sleeves, or anything else that could be snagged by the fan or by a belt, lest you be strangled or torn apart.

Could you describe the noise? Does it make the noise based on engine speed or car speed?