Just bought a used 2005 Grand Caravan with 3.8L engine. I have noticed a low pitched hum type noise (frequency similar to a ships foghorn except not loud) when driving approx 35-50 MPH on level or beginning a slight uphill. The sound only occurs during slight aceleration. I suspect it is air intake related to engine vacuum but not sure where to investigate since it only occurs during driving conditions. Any hints or suggestions would be appreciated.

 

Hi,

My father had the same type of problem with his van, it turned out not to be a vacuum leak. If it is a vacuum leak, the van could idle low and rough. Depending on where it is, you could also loose you interior air vents.

This is what his ended up being, he complained to me about a hiss when accelerating. It was the air intake hose,or breather hose. I found a small crack in his and replaced it. His is a 3.3L, but your 3.8 will have the same hose.




Good luck!

 

I checked the vent hose to the front valve cover and it fits tightly at both ends. I removed the airfilter box and large connecting hose to the air intake at the throttle valve and everything appears to fit properly and in good condition. The noise is directly related to the throttle position when running under a very slight load on the engine. Let off the gas peddle and the noise goes away, slight pressure on gas peddle and noise occurs, more pressure on gas peddle and noise goes away. Problem is that I always try to drive without using a lead foot so I hear the noise a lot.

 

Hey I was wondering if you ever figured this out? I was told it might be power steering related or fuel pump related but im really not sure. What did it end up being for you?