Noisey fuel pump?
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john hughes
- Joined: Tue 10 Feb, 2015 20:52
- Posts: 1
Noisey fuel pump?
Hi I have just bought a very nice low mileage 43000 mls 2001 2.2 which I am very pleased with but I have never owned a convertible before an wondered if is normal to hear a noise like a motor coming from the back of the car could it be the fuel pump and if it is, is it normal to be able to hear it?
Re: Noisey fuel pump?
2.2 - good choice! Hope you're enjoying your new car 
Do you hear the noise constantly or is it motion related?
The fuel pump is located in the rear chassis panel behind the driver's seat. There's a seam in the carpet that can be pulled back to access the pump. I've not heard of reports of pumps making noise, but others have greater expertise and will likely jump in here! Not difficult to replace if it's broken.
Other things I've encountered: the diff can make noise - in which case I'd suggest a fluid check/change. Shock mounts rattle too. If there's vibration too, check the propshaft mount. Hope you get it sorted as a quick fix.
Enjoy the car. And post some pics!
Tom
Do you hear the noise constantly or is it motion related?
The fuel pump is located in the rear chassis panel behind the driver's seat. There's a seam in the carpet that can be pulled back to access the pump. I've not heard of reports of pumps making noise, but others have greater expertise and will likely jump in here! Not difficult to replace if it's broken.
Other things I've encountered: the diff can make noise - in which case I'd suggest a fluid check/change. Shock mounts rattle too. If there's vibration too, check the propshaft mount. Hope you get it sorted as a quick fix.
Enjoy the car. And post some pics!
Tom
2002 BMW Z3 2.2i 82k
1971(K) MGB GT - the 'other' car
1971(K) MGB GT - the 'other' car
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Southernboy
- Joined: Thu 07 Oct, 2010 12:39
- Posts: 6436
- Location: Johannesburg
Re: Noisey fuel pump?
Not ever heard the fuel pump.... I suggest it may well be a drive-line related sound. As stated above, the fuel pump is located directly behind the driver seat inside the fuel tank. It is covered over by the fitted carpet which in that area is probably about 50mm thick. I doubt you are hearing that.
Possibilities are the diff, which on the Z3 is literally to your left and slightly behind...in fact the diff is just ahead of the fuel tank, so it will be under the rear storage box as a direct line downwards. The cause of the diff "whine" was explained to me by a BMW mech here as being caused by "resonance" created in the axle carriers which extend left and right from the diff carrier area.
He told me that on M cars the axle carrier was filled with small metal shot to add extra weight to the rear axle so that it would reduce wheel spin with the M power. It also nullified the diff whine as a side effect. Because the axle carrier on all the cars have several holes in them they need to be plugged with rubber grommets and then use some expanding poly foam to fill it up on both sides. He suggested doing the foam insertion first, then trimming away any excess foam which will have escaped from the holes before fitting the rubber grommets.
One thing about the foam, you need to have a fine water spray bottle handy - the inside of the carrier - in this instance - needs to be finely "wetted"...this apparently ensures the foam doesn't clog before it has filled all the vacant spaces in the carrier. BMW here use this as a standard "cure" when customers come in complaining about the "diff whine".... Den Braven make excellent high density fast curing poly foams which is what he tells me they make use of. He tells me the application puts an end to the resonance / whine.
I went the "sound proofing route. I applied a layer of "builders flashing" to the entire boot area under the carpets. This had the effect of dampening the resonance of the boot volume which only adds to the whine. Builders flashing is essentially a roll of butyl with a very thin malleable layer of aluminium sheet / foil on one surface, and a release paper on the other surface. It'll stick extremely well and also adapts to the contours and shapes of the pressed metal body inside the boot. It's relatively light weight, and can be used inside the doors on the outer skin as well as the footwell voids behind the speakers. This reduces the "road noise" and improves the effectiveness of the sound system too. It's cheap and easily applied, cut to shape etc etc...
Another area worth investigating is the drive shaft (prop shaft)...it has a center bearing just aft of the gearbox. This bearing supports the shaft which is made in 2 sections. If that bearing rubber casement is worn or deteriorated, it will make some noise when driving.
You need to establish if the noise occurs when the car is in motion or if it also is heard at standstill. If it's detectable only whilst driving, you have a motion related cause - if it is heard whilst stationary, the possibility exists that you have a vibratory cause or indeed a faulty fuel pump. The underside of the central tunnel has several aluminium heat shields fitted. These are held to the underbody by small self tappers. It is common to have screws fall out, or the aluminium being bent by bottoming the car on a speed bump or even a large stone smacking one of them so it is in contact with the underbody. A thorough examination of these shields will eliminate that. Also check exhaust mounting brackets and rubber sling supports while you have the car raised.
I suspect your description of a noisy fuel pump means you are hearing what sounds like an electric motor - in which case, it's most likely the diff. Nothing to worry about, but annoyingly intrusive nonetheless.
Possibilities are the diff, which on the Z3 is literally to your left and slightly behind...in fact the diff is just ahead of the fuel tank, so it will be under the rear storage box as a direct line downwards. The cause of the diff "whine" was explained to me by a BMW mech here as being caused by "resonance" created in the axle carriers which extend left and right from the diff carrier area.
He told me that on M cars the axle carrier was filled with small metal shot to add extra weight to the rear axle so that it would reduce wheel spin with the M power. It also nullified the diff whine as a side effect. Because the axle carrier on all the cars have several holes in them they need to be plugged with rubber grommets and then use some expanding poly foam to fill it up on both sides. He suggested doing the foam insertion first, then trimming away any excess foam which will have escaped from the holes before fitting the rubber grommets.
One thing about the foam, you need to have a fine water spray bottle handy - the inside of the carrier - in this instance - needs to be finely "wetted"...this apparently ensures the foam doesn't clog before it has filled all the vacant spaces in the carrier. BMW here use this as a standard "cure" when customers come in complaining about the "diff whine".... Den Braven make excellent high density fast curing poly foams which is what he tells me they make use of. He tells me the application puts an end to the resonance / whine.
I went the "sound proofing route. I applied a layer of "builders flashing" to the entire boot area under the carpets. This had the effect of dampening the resonance of the boot volume which only adds to the whine. Builders flashing is essentially a roll of butyl with a very thin malleable layer of aluminium sheet / foil on one surface, and a release paper on the other surface. It'll stick extremely well and also adapts to the contours and shapes of the pressed metal body inside the boot. It's relatively light weight, and can be used inside the doors on the outer skin as well as the footwell voids behind the speakers. This reduces the "road noise" and improves the effectiveness of the sound system too. It's cheap and easily applied, cut to shape etc etc...
Another area worth investigating is the drive shaft (prop shaft)...it has a center bearing just aft of the gearbox. This bearing supports the shaft which is made in 2 sections. If that bearing rubber casement is worn or deteriorated, it will make some noise when driving.
You need to establish if the noise occurs when the car is in motion or if it also is heard at standstill. If it's detectable only whilst driving, you have a motion related cause - if it is heard whilst stationary, the possibility exists that you have a vibratory cause or indeed a faulty fuel pump. The underside of the central tunnel has several aluminium heat shields fitted. These are held to the underbody by small self tappers. It is common to have screws fall out, or the aluminium being bent by bottoming the car on a speed bump or even a large stone smacking one of them so it is in contact with the underbody. A thorough examination of these shields will eliminate that. Also check exhaust mounting brackets and rubber sling supports while you have the car raised.
I suspect your description of a noisy fuel pump means you are hearing what sounds like an electric motor - in which case, it's most likely the diff. Nothing to worry about, but annoyingly intrusive nonetheless.
Re: Noisey fuel pump?
Most new Z3 owners complain about the diff whine in the first few months.
Just like the wife --- you get used to it after a while.
Just like the wife --- you get used to it after a while.
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Southernboy
- Joined: Thu 07 Oct, 2010 12:39
- Posts: 6436
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- Location: Johannesburg
Re: Noisey fuel pump?
I can definitely hear my fuel pump, even when the car is idling. I had to change out the fuel pump since 14 years of fuel caused mine to stick and burn out when rebuilding the car. I bought a used one which also come from a car that had be lying for a good length of time, must keep an eye out for a spare/upgrade just in case.
