Unusuall noise

[aaronlittle]

Guys, lots of interesting posts and some great posts but haven't found an answer to this problem. A couple of people seem to have the same problem but there are not any good fixes. Car goes to dealer on Thursday, want to give them a steer as the first dealer I tried was useless (I am sure I know more about cars than them!)

XC90 R Design 2009. Drives fine, no other problems.

When you accelerate gently, as you hit 40mph there is a noise that can only be described as sounding like a blown exhaust / farting sound (yes laugh...). When the noise is there, it seems to correlate with engine speed / noise but is completely distinct from it. It is accompanied by a light vibration in the footwells / pedals. It sounds as if it is right behind the stereo.

As you continue to accelerate it goes, then returns around 70 mph...you can drive at a constant particular revs/speed around 60-70 and make it make the sound constantly but as you accelerate it goes away.

If the car is heavily loaded, the volume of the noise increases significantly...but you can accelerate through it again, by 80mph it goes away. I cannot get this volume increase simply by revving harder or going faster.

No noise in neutral or park when the car is revved.

I think it is starting to make the noise very quicetly at low speeds but difficult to distinguish.

Been to one dealer and had new software installed (is this code for "we parked it in the corner and had a cup of tea until you came back?").

My gut instinct is it is a transmission probelm but any thoughts welcome.

[ianu]

...does it lose power at all - or hesitate slightly ? Only a suggestion - check all the intake hoses - turbo, Air filter etc especially high pressure side if possible.
Can you hear any sign of exhaust leak either under the car or under the bonnet when it's ticking over ?
Does it smoke more than normal ?

That's my starter for 10 ???

Cheers
Ian.

[aaronlittle]

thanks for the thougts ian. no discenable loss of power, one of the additional reasons i think it might be something in the transmission rather than engine. will check round hoses, etc.

welcome any other suggestions

[keithmcc]

Is it at particular engine revs under load? If you use manual over-ride to select specific gear, does it come in at same engine speed in different gears? Or is it actually road speed?
Are all engine and exhaust mounts OK?

[keithmcc]

Is it at particular engine revs under load? If you use manual over-ride to select specific gear, does it come in at same engine speed in different gears under load? Or is it actually road speed?
Are all engine and exhaust mounts OK?

[aaronlittle]

thanks, it kicks in around 1800-2000 revs, this seems to be consistent. ive flipped it into manual and it does the same. i havent had the engine mounts checked and replaced yet, i am wondering having read other posts whether this would be a good starting point.

[Kaymos]

I have similar noise. Starts at 35/40mph... Louder with acceleration. When stationary, bonnet up & checking where it's coming from, press accelerator & omg is loud, top left of engine (forward of steering wheel).

[polar bear]

Has it got polestar on it, If so test on an incline stop start and on the change
from !st to 2nd is it more regular

[aaronlittle]

Just thought I would post update. Went into the garage and they installed new engine mounts and an upgraded propshaft mount (apparently this is a known problem) which cured it.

[the masked avenger]

Bingo, thanks for this the same noise has been troubling me for a while......was praying it was not something major!