Hi,



I have an '06 Mariner Luxury AWD, which I bought last November. About
two months ago, I started hearing hissing noise during
acceleration. I went to the dealer and he went on the road with
me, and he said that he didn't hear the noise, and that it's probably
just the intake. He checked for vacuum leaks, and said everything
was fine.



Since about almost a week ago, it has gotten worse. Now it sounds
like air trying to escape through a tiny opening. A good example
would be like a pressure cooker. And, I hear these noises only
when the car is in "drive." I tried accelerating with the car in "park"
and I did not hear the hissing.



I went to the dealer again yesterday, and I let him drive the car and
he agreed that he heard the noise and said that it may be a vacuum
leak. So he checked everything and said he didn't find anything. He
said that if something is wrong, it will get worse and therefore, will
be easier to find out exactly what's wrong.



Does anyone have any idea on what may be causing this noise? Any help would be appreciated.



Thanks

Just to add to my previous post, it starts out as a "hissing" sound but once the engine is warmed up, it turns into more of a "whistling" sound during acceleration.

I have not gone back to the dealer yet mainly because I want to be able to describe the problem accurately and not sound like a fool. I don't think it is anything alarming (although I was hoping it would get worse so they could finally find out what it is), but it is annoying because this a fairly new vehicle.

If anyone could help me identify what the problem is, I'd greatly appreciate it.

Thanks in advance.