99 740i high-pitched electronic hum

Hi folks,

I am experiencing an annoying bug in my 99 740i which happens after the car gets up to operating temperature: when I step on the brakes (even if slightly), a high-pitched hum can be heard even from within the cabin, windows up. When I step outside, the hum is even more pronounced. This hum persists for about 30 seconds, then begins to fade away.

However, when I'm in stop-go traffic, the hum (or drone) is incessant, because I have to brake frequently.

I leased the car, BMW certified, from a BMW dealership and it is under warranty. The car has 28K miles.

I would appreciate hearing from other similar-vintage BMW drivers who have experienced this problem. Any ideas or thoughts are welcome.

Thanks in advance,

Scarab
[email protected]

Possibly the fuel pumps? I have a 1990 and had a similar problem with a hum until I replaced mine. Just a suggestion.

wlerner:

Thanks for your response. The service manager at BMW heard the hum/drone/whine, and explained that on hot days, the fuel pressure builds up and creates the noise. He says it is normal.

I've consulted with other forum members, who suggested the fuel pump is going bad.

Did your hum/whine get progressively worse until it failed??

Thanks for your input again, Scarab