Roaring engine intake sound when in low speed

[rogerkiu]

Hi all! Recently I found that my X' engine had roaring sound when driving at low speed around 30Km/h or below sometimes. It only happens when the speed is low and in 1st gear and 2nd gear, like driving in car park or start off at green light. The sound turns normal after the speed climbs above 30Km/h. I can hear the roaring sound when I am in the car and close all the windows with A/C on. The sound just seems like diesel car does.

I also noticed that the engine RPM was normal (around 1000 to 2000 RPM) when the roaring sound appears and everything is normal, no power lose or decrease. The gearbox runs also normal. The problem is ony the sound.

Just want to know anyone here has the same experience and what is going wrong with my X? Thanks for help!!!

[nicolak]

Just a fan clutch staying locked longer (higher ambient temps, using A/C, worn clutch, etc). I would not be terrible concerned.

[rogerkiu]

I understand it, but this sound only comes when I press gas. It seems that the engine is taking very deep breath when in low speed. It seems the engine needs more fresh air for combustion. I don't think it is the fan sound. Could it be somewhere leaking air? However, no power lose or reduce when speeding up. My gearbox also work normal. Please give me some advice. Thanks a lot!

[lemans4.8]

yeah, i noticed the same in my '05 4.8.... It's hard to describe the sound but the growl's pitch goes "up-and-down" repeatedly, kind of like an older diesel engine at idle (but a little slower)

Are you running an aftermarket intake or air filter? I'm running a Greenfilter in the stock intake box and I just figured it was the excess air going into the engine....

[manonskisjr]

YES, my car just started doing the same thing 02' 4.4. Its exactly how you described it. I replaced my air filter and that didnt do crap. It sounds like a diesel semi sucking in way too much air.

Anyone else have any feedback? I'm stumped.

[tonycajjo]

Originally Posted by nicolak

Just a fan clutch staying locked longer (higher ambient temps, using A/C, worn clutch, etc). I would not be terrible concerned.

remove the fan and see if it goes away, but dont drive for long without one to avoid overheating. a worn / broken fan clutch will sound like that.

[rogerkiu]

Yesterday, I check the pressure of my tires and found that the presure were only 30 PSI, then I pumped the presure to 35 PSI. Today I drove my X to work and found that the roaring sound went away. I will try to drive her more to see if the sound goes back. Will update all of you.

[rogerkiu]

Originally Posted by tonycajjo

remove the fan and see if it goes away, but dont drive for long without one to avoid overheating. a worn / broken fan clutch will sound like that.

It not come from the fan, it comes from air intake system.

[rogerkiu]

Originally Posted by lemans4.8

yeah, i noticed the same in my '05 4.8.... It's hard to describe the sound but the growl's pitch goes "up-and-down" repeatedly, kind of like an older diesel engine at idle (but a little slower)

Are you running an aftermarket intake or air filter? I'm running a Greenfilter in the stock intake box and I just figured it was the excess air going into the engine....

Yes, about one month ago, I renewed air filter element with OE BMW part and the roaring sound came after the replacement. One week ago, I also renew the MAF sensor with OE BMW part, the sound still existed.

[rogerkiu]

Now I believe the roaring sound has gone. After I pump my tires to 35 psi, the roaring sound disappered. Now the engine sound backs to normal and feel very good. I cannot think out any linkage between roaring engine sound and tire presure, but it really works on my X. Anyone of you who encounters this problem may have a try.