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Discussion Starter · #1 · (Edited)
Lately, I've noticed a buzzing noise coming from the engine when it's turning at about 2500 to 3000 RPM. The noise is most prominent under load in 2nd and 3rd; but it's audible in other gears and in neutral, but not as distinctive.

The engine itself appears to be operating normally - no changes in output or performance.

At first, I thought it was heat shield hitting the frame somewhere, but I've jacked her up and crawled underneath several times and I can't find ANYTHING that looks like a source of the noise.

Now I am worried that it might be engine internals (water pump? fuel pump?)

Anyone have any ideas? I've searched archives on the board but can't find any previous posts that describe something similar.

Thanks
Jeff :cheers:
 

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x703jko said:
Lately, I've noticed a buzzing noise coming from the engine when it's turning at about 2500 to 3000 RPM. The noise is most prominent under load in 2nd and 3rd; but it's audible in other gears and in neutral, but not as distinctive.

The engine itself appears to be operating normally - no changes in output or performance.

At first, I thought it was heat shield hitting the frame somewhere, but I've jacked her up and crawled underneath several times and I can't find ANYTHING that looks like a source of the noise.

Now I am worried that it might be engine internals (water pump? fuel pump?)

Anyone have any ideas? I've searched archives on the board but can't find any previous posts that describe something similar.

Thanks
Jeff :cheers:
Still under warranty? Have the dealer check it out.
 

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I had similar noise with accompanying vibration, came on at particular rpm but can't remember exactly where. It turned out to be the alternator going bad. Replaced under warranty.
 

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Discussion Starter · #4 ·
Chuckc said:
Still under warranty? Have the dealer check it out.
Expired and they have checked - suspected a cat. Replaced that (under 8/80)...no joy.

Jeff cherrsagai
 

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Discussion Starter · #5 ·
LBPDNNM5 said:
I had similar noise with accompanying vibration, came on at particular rpm but can't remember exactly where. It turned out to be the alternator going bad. Replaced under warranty.
Sounds plausible. Thanks for the input.

Any other ideas?

Jeff :cheers:
 

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Jeff,

How's it going? Are we going to see you again at a M5DE? (E60?) The noise you are hearing, if it's metallic could be a loose alternator mount or heat shield.


John
 

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If it is audible in neutral, buy a mechanics stethoscope (will cost you US$ 10 or so) and listen around until you have localized the source.

You can also put another person in the car to change the revs. And you can do that with the car lifted so you can access it from benieth.

David
 

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Discussion Starter · #8 ·
DavidS said:
If it is audible in neutral, buy a mechanics stethoscope (will cost you US$ 10 or so) and listen around until you have localized the source.

You can also put another person in the car to change the revs. And you can do that with the car lifted so you can access it from benieth.

David
David. I'll give that a shot if my tech can't scope it out. Jeff cherrsagai
 

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Jeff,

Did you ever solve this problem? I have an E39 M5 with a similar vibration issue and I'm looking for solutions.

Thanks.

Roland.
 

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Roland, has this vibration been present since the car was new or is it a new vibration.
 

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Mike, I bought the car recently with 75,000 kms on the clock (approx 45,000miles), so I don't know when the vibration first arose. It's a 2000 model. I'm sure the vibration cannot have been there from new because it's pretty intrusive and would not have been tolerated in a new car.

The vibration can be felt with the car stationary by just running the engine up through its rev range and it's also very noticeable when the car is moving. You can feel is under your feet in floor in front of the driver's seat, through the clutch rest and through the gear stick. It does not depend on engine load; you can feel it even when the car is cruising. It appears to be a function of engine speed rather than road speed.

I have ben advised that it is most likely caused by engine mounts that are in need of replacement. I understand that they are fluid-filled and can collapse after a number of years. Any other advice will be greatly appreciated.

Roland.
 

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do you know if the clutch is original? I had a vibration arrise from an incorrectly installed clutch.
 

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Mike, the clutch is not original. When the dealer inspected the vehicle as part of their pre-sale preparation they found the clutch was slipping and agreed to replace it. I did not drive the car before the clutch was replaced, so it';s quite possible that this is the cause of the issue. However I have been told that it's nearly impossible to install a BMW clutch incorrectly and that they are always in balance.

Can you explain how it is possible to install the clutch incorrectly? Do you know the detail of what was wrong with your vehicle?

Roland.
 

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There are a number of ways to screw up a clutch install.

For example: The guide dowels for the gearbox to bellhousing connection, and the dowels for the bellhousing to engine block are easy to damage causing a misalignment of the shafts.

Then it is easy to grease the splines in which the clutch pressure plate slides in the wrong way, making the clutch movement sticky.

Clutch break-in procedure is very important, but most of the time the SA does not tell the customer how to do it properly.

Often, the propeller shaft is left hanging down unsupported from the mid support bearing forward. This is extremely bad for the universal joint, and could be the source of the vibration.

Also, if the propeller shaft at reinstall is rotated relative to its previous orientation to the gearbox output shaft, it could affect balance adversely.

The most common vibration problem comes from the exhaust. Grab the tail-pipes when cold and shake vigourusly in all directions. Any noise? Then the exhaust is not seated properly. If so, slack and retighten all the mounts. Then retest.

David
 

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David,

OK - thanks for the advice. The dealership has previously "re-hung" the exhaust to ensure that was not the problem - it did not help. I don't think the problem is related to the universal joint in the tailshaft because it is present event when the vehicle is not moving if one simply revs the engine. The whole car sounds and feels rather "agricultural" or "tractor-like" as one friend put it. Not like a BMW at all. I have ordered new engine mounts which are being air-freighted in from Germany. I'll let you know how I get on. Thanks again,

Roland.
 

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x703jko said:
Lately, I've noticed a buzzing noise coming from the engine when it's turning at about 2500 to 3000 RPM. The noise is most prominent under load in 2nd and 3rd; but it's audible in other gears and in neutral, but not as distinctive.

The engine itself appears to be operating normally - no changes in output or performance.

At first, I thought it was heat shield hitting the frame somewhere, but I've jacked her up and crawled underneath several times and I can't find ANYTHING that looks like a source of the noise.

Now I am worried that it might be engine internals (water pump? fuel pump?)

Anyone have any ideas? I've searched archives on the board but can't find any previous posts that describe something similar.

Thanks
Jeff :cheers:
I had a similar sounding problem on a previous vehicle (non-BMW).
Turned out to be a large stone lodged between the exhaust manifold & car body. Clearances are small.
Also, the stock exhaust downpipes are "two-ply". Is the inner pipe possibly rusting & rattling at a certain resonant frequency?
You never know...

Good luck.
Salty.
 
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