Hey all!

This isn't really "beneath the bonnet" but it's the closest category for this thread.

I've recently noticed a new noise and I was hoping someone would be able to help me trace its source. I'll describe it as best as I can:

- It sounds like a motor whirring (or a Dremel tool running at half speed). I'm guessing that it's some sort of motor because the pitch of the sound dips when I budge the steering wheel. I'm almost positive that it's not the power steering motor because I'm familiar with that sounds like and, furthermore, when I budge the steering wheel, which increases the pitch of the power steering motor, the pitch of the mysterious noise simultaneously drops as if the power steering motor is drawing current away from whatever's producing the noise.

- The noise emanates from the gas tank area. I removed the rear seat bench but I can't pinpoint the location of the noise because it's pretty much everywhere where there isn't sound-damping material -- it's equally loud over the center hump and over the two black metal circles in the seat basins.

- The noise isn't terribly loud but it's always there when the engine's running. It's most audible at standstill when engine or road noise doesn't mask the sound.

- The climate controls don't seem to affect the noise. Turning the fan, recirculator, a/c, or vents on and off doesn't change the noise.

Could it be the fuel pump? I couldn't tell from the realoem.com diagrams where the fuel pump is located. Are there any other electromechanical devices in the fuel tank area? Do I have a Cuisinart in my fuel tank?

I am stumped. What do all you MINI pathologists think?

 

You are probably hearing the fuel pump or a noisey syphon jet. Put your ear up to each side of the tank (from under the car) and try to ID which side it is from. Also see if you can hear it with engine off and the key in the start position. The pump will be on for about 15 seconds in this position.

 

Thanks, 002!

I didn't hear the noise with the engine off and the key in the start position but I was able to determine that, from the outside, it's louder on the driver's side... which is strange because, looking underneath the car, it appears that the ventiliation stuff is on the passenger (right) side. But I don't know what I'm talking about so...

What does it mean if the fuel pump or syphon jet is noisy? I presume neither should be so are they about to break down?

 

The fuel pump is on the left side. So that's where I'd start investigating. Bmw usually uses a syphon jet to get the fuel on the right side over to the left side. I have come across a few of these on bmw's that were noisy. I don't know if that means it is about to brake because we don't have time to find out at the shop. The noise went away and so did the car. The manual doesn't describe the system very well, so I can't say 100% that is uses this system. I will look more into this system and let you know what I find.

For the fuel pump, it could be going bad or the fuel filter could be clogged and causing extra strain on the pump. Do you hear it at all fuel levels or just
on empty?

How many miles? If you are in waranty, just take it in and they should do the rest. If it's on you, I would check fuel pressure and watch for driveability symptoms like hesitation when accelerating that gradually get worse over time. I'm not sure what your skill level/means are and that has a significant affect on the course of action.

 

What are you running for tires? I noticed, that when I remove my rear seats I had lots of noise directly related to road speed, not throttle; I worte it off as having low profile wider tires making the sound. Description of the sound matched yours exactly until you mentioned the noise at idle.

 

I would agree with the fuel pump as the most likely source of the noise.

As a general rule, a fuel pump should last for at least 100K miles. Sometimes, with age, the fuel pump will make more noise than it did when new. This increased noise can occur even though there is no obstruction of the fuel inlet/pickup point; it is just a manufacturing tolerance/whatever issue. If that is the circumstance (higher pump noise but no obstruction issues), you have to decide how badly you don't like the noise and is it worth the cost of replacing the fuel pump for just a noise issue? (And there is no guarantee that the new fuel pump won't develop a similar noise at some point after installation.)

 

In the AM turn your key to position 2 and then listen. You will hear the fuel pump start to do it's thing.