hey. so i just got an '83 300 TD. I have a strange sound that I was wondering about. Some sort of road noise....almost like it woudl be coming from the tires or something...just a heavy humming. Gets louder and slightly higher in pitch as I accelerate and once and a while (not sure if its related) there is a very quiet whine that sounds just like a siren. If I'm going 60mph and hit the brakes to de-cellerate the humming stops while hte brake pedal is depressed. Any thoughts?

Could be a few things, but I'm thinking it's possibly a wheel bearing. Though the sound going away under braking is strange.

Can you provide any more details such as where you think the sound is coming from? Is it when you brake or also when you let off the accelerator?

The siren-like whine is probably the turbocharger. Not unusual or a problem.

Try having someone else come with you to sit in both the front and back seats to listen where the sound is coming from. It can be hard to isolate sounds from the driver's seat. Someone else, not driving, may also notice other patterns or attributes to the sound.

Also you say it's a hum. Are you sure 'hum' is the right word? Or is it a rubbing or mild grinding noise, maybe?

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

Are you running studded tires?

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

If the whine is coming from the rear of the car its the differential gears meshing and making noise due to age/mileage.

You might find a shop with a dynamo. They can put it on the thing and run the drive wheels to see if the sound is originating from them. Should cut your diagnostics in half.

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Codifex
1981 240D ChinaBlue (Got her running with a donor engine.)
1983 300DTurbo w/sunroof.
1984 300TD manual sunroof. (Electrical Gremlins)

sorry for the delay in response. yes the sound goes away when i brake hard..but only while the brakes are applied. the accelerator does not effect it. neither myself nor a passenger could locate it other than to say its coming from the front of the car. i'm not running studded tires but i assume its almost the sound that studded tires would make.

if there is anything i can do to try and troubleshoot it myself that would be great, but if i have to bring it to a shop to use the dynamo (as suggested) then i guess i'll do that.

thanks folks

I vote wheel bearing as well. When braking you "center" the bearing. That compensates
for wear for a bit. If I'm being stupid disregard.

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85 300TD FED-Daily
84 300SD-Wife's
86 XJS-Sunday
66 GMC-Work- Given to my stepson
83 BMW Airhead- Given to my stepson

X2
Jack each front wheel up & rotate by hand. You should be able to feel any wheel bearing problem.

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Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving

I had a bad rear wheel bearing and it made a very distinct "growl" from the back while driving down the road. Sometimes I could make it change by swerving from side to side to change the loading on the bearing. If it's a rear bearing, it will get louder and more annoying pretty steadily.

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1981 Mercedes 300TD, 1994 Honda Civic Del Sol
http://mefi.us/images/fuelly/smallsig-us/67195.pnghttp://mefi.us/images/fuelly/smallsig-us/103885.png

dragging brake caliper? Brake pads ok?

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1985 300d smoke silver/red int. (204k) <--Sadie the 80's Mercedes from Hades!
1985 300TD 587 cabernet red/155 Creme (143k)
2007 Ford Expedition EL (54k)

"Seems to me you bought a hobby... not a car" - My dad.