I have a bit of a noise going on in the motor compartment. Let's see if I can discribe it. First off it's a 300 Turbo bet that will help.

Sounds like valve train noise or maybe a pinging. I noticed it at around 65 MPH (2400 to 2800 RPM) with no load. What I mean by no load is that I'm on the flats. If I decellerate or accellerate the noice goes away. I can only hear it with the windows rolled up. It's almost sub-audible. Kinda like a high RPM nailing. Almost like playing cards in the spokes of a bicycle (Now I'm really showing my age).

Any ideas?

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1984 280SEL, 62,000 miles
Euro model in the USA
1983 300D (Totaled out 10/2004)
New Factory Mint Green paint
Palomino int
1982 240D (Steak dinner for two)

This is probably a bad guess, and I have no idea what a valve train noise sounds like. Nor a high RPM nailing. But the cards in the spokes I do know what it sounds like. (we ain't that old, and how much you wanna bet, kids still do it today?).

Anyways, just had a situation with my car recently, sounded like a loose screw in the shifter area. I looked around like crazy for that, and had a magnetic thing to see if one had fallen down in there. Finally posted it up on the forum, people told me it was the shifter bushing underneath the car. Sure enough, that's what it was. $1 part. I posted something on the DIY instructions if you need it. Other people's have sounded different, depending on how bad their bushing got. But basically, it can be rattling when you drive.

Just a thought. A maybe a wrong one, but trying to help.

Jeff 1991 300d, 102k

In my limited capacity and fly by the seat technology it maybe the turbo over boosting. I have checked for vacuum and pressure at the wastegate diaphragm and it's leaking. The over boost protection switch may also be bad. I have not checked boost pressure yet but with a bad wastegate diaphragm it's has to be too high.

Anyone ever:
Replace the wastegate diaphragm with the turbo still in place?
Any nice places to place a boost pressure gauge?
Any part numbers or sources for the diapragm?

Good thing my hearing and ass sence toll me to back out of it before I scattered it

__________________
1984 280SEL, 62,000 miles
Euro model in the USA
1983 300D (Totaled out 10/2004)
New Factory Mint Green paint
Palomino int
1982 240D (Steak dinner for two)

I've seen a nice mounting in one of the center dash vents.

__________________
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

You may have an exhaust leak causing the sound. Depending on which turbo you have (KKK or garret) it may be easier to just pull the turbo. Before you do that check the wastegate hose and put in a boost gauge. Here is where I have mine:

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine