Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help

Go Back   PeachParts Mercedes-Benz Forum > Mercedes-Benz Tech Information and Support > Tech Help

LinkBack Thread Tools Display Modes
Old 12-02-2004, 08:28 PM
Registered User
Join Date: Nov 2004
Posts: 119
humming sound from rear or 300E

I have a 1990 300E and its a 4matic. There is a humming or whining sound coming from the rear. It kinda comes and goes as I push and release the accelerator. My 1999 4matic never made this sound. It has 90,000 miles which is pretty low for a 90'. Could this be the normal sound of the fuel pump? Or is my rear end about to blow up. Its not super load or anything, but it is noticeable. Thanks guys. Its the 3.0 motor. solid but ohh so sloooowwwww
Reply With Quote
Old 12-02-2004, 08:38 PM
Gilly's Avatar
Registered User
Join Date: Mar 2001
Location: Evansville WI
Posts: 9,616
If it's doing it in neutral or park, I'd assume fuel pump or exhaust system. If it's in drive (car moving) I'd guess differential.
If this car is really really slow, make sure the throttle valve cable is connected (under the air cleaner).
Reply With Quote
Old 12-03-2004, 02:22 AM
Gunawan's Avatar
Registered User
Join Date: Sep 2002
Location: Jakarta, Indonesia
Posts: 23
Hi guys,
my car 1988 300e is doing the same. I noticed that when the fuel is running low, the humming is louder. But if I fill the tank up, the humming dissappears. I think it has something to do with the fuel pump intake or fuel backflow inside the tank. Because it didn't harm the performance, I don't do anything about that. I hope milhan's problem is the same. By the way, for your information. I changed one of the two fuel pumps before.
Reply With Quote
Old 12-03-2004, 04:22 AM
Posts: n/a
The diesel version of these 124's also have been known to make the same or similar sounds including my 87 300D. Diesel 124's have no fuel pump in the fuel tank or anywhere back from the engine.

At approx 50 mph, I can begin to hear a hum that will rise or fall depending on how much I push the accelerator. The more throttle, the louder. Let off the throttle, the hum softens to quiet. After reaching 55 mph, the hum sound dissipaits to no sound at all. The hum is only there between 50 and approx 57 mph.

Sound familiar?

Possible causes may be worn wheel bearing, or worn or loose differential ring bearing.

I have driven 30K with the hum and it has not changed at all, and I'm not worried about it. If the sound gets louder, or spread over a wider range, I'll pay it more attention. BB
Reply With Quote
Old 12-03-2004, 11:06 AM
haasman's Avatar
Registered User
Join Date: Jun 2001
Location: San Francisco, CA
Posts: 3,097
[IMG]Both the 190e and the 300e have differential whine that is only noticeable on the highway, they both have over 230k miles on them. The telltale is the lifting of the gas pedal and applying it.

I started using 90w-140 differential oil in the 190e and it seemed to quiet it down a bit.

I read also on this site where someone recommended Redline's synthetic diff oil. I haven't tried it though.

Attached Thumbnails
humming sound from rear or 300E-300e-1-small-.jpg  
'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)
Reply With Quote
Old 12-03-2004, 11:17 AM
Posts: n/a
I forgot to mention that I have changed out the diff oil with Moble 1 synthetic diff oil, (sae 75-90 I think) and no changes but there is a little leakage, not bad, but I do keep an eye on that! BB
Reply With Quote
Old 12-05-2004, 06:48 PM
Registered User
Join Date: May 1999
Location: Sacramento, CA
Posts: 1,472
This happens on my 87 300E from time to time. In my car, it also gets louder when you step on the gas, and then seems to quiet down when you release it, although sometimes it can get very loud without any pedal movement, and I've had it show up when the engine is off (!) too.

I discovered a little while ago that if I stop the car, walk around to the rear, and crack open the gas tank cap for a second, it seems to depressurize the fuel tank and the whining stops. I don't know what this means, or why it does that, but thought that it might be helpful.
2000 C 2 3 0 Sport :: 180k
Reply With Quote
Old 12-05-2004, 07:34 PM
Registered User
Join Date: Nov 2004
Posts: 119
Interesting, I will try that. It sure is annoying.
Reply With Quote


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On

All times are GMT -4. The time now is 06:11 PM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page