My 81' 240d will make a whistle from about 2000rpm to about 3000rpm, you can't hear it at all with the windows up, but it's fairly loud from outside the car and with the windows down.

I can't figure out what it is, I haven't noticed any loose vacuum tubes, but it sounds like a vacuum leak.

Any ideas?

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'95 Geo Metro 3-cyl 5-speed
'97 Geo Metro 3-cyl 5-speed x2
'81 Mercedes 240D 4-speed manual RIP

Does it happen when the engine is fully warmed up? If so it could be a water pump bearing issue apart from the perceived vacuum issue.

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99 Gurkha with OM616 IDI turbo

2015 Gurkha with OM616 DI turbo

2014 Rexton W with OM612 VGT

Two months ago,I dreamed my intake and exhaust manifolds,and turbo fell of.To my amazement all my bolts needed a full turn.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran

Dose it make the same noise when the car is on the road and when the car is standing still and reved up?

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84 300D, 82 Volvo 244Gl Diesel

1. A whistle is almost always an intake ( of some sort ) leak.
2. use an oil squirter around the suspect areas... when it stops you have located the area of the leak.
3. start low and work high on things like the manifold so that gravity will not mislead you.
4. then clean up the mess you have made.

Air cleaner lid not on correctly? base of air cleaner not secure to intake?

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81 300CD (sold) 1972 280 SEL 4.5 (sold) 1966 250 S 4 spd (sold) 1974 450 SL (sold) 86 BMW 325ES (sold), 1973 280C (sold) 1988 300 SE.

my whistle was a big old exhaust leak.

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1996 E300 110,000
1985 300TD 212,000
1980 300D 238,000

So was mine - right around one of the bends. Jim

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Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

the last whistle i had to find on a diesel turned out to be the rear muffler causing the noise, there was something internal causing this, i was able to find it by having someone rev the engine while i listned at the muffler.

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1967 250 S
1967 280SE
1968 250S
1971 280 SE
1973 220
1974 280 S
1975 450 SEL
1976 220 D
1979 300SD
1983 300 SD
1985 230 TE euro
1986 280SL
1986 500 SEL euro
1986 190E 2.3
1990 300 SE
2003 C230 K
2004 C230 K
1987 560SEL
1987 300SDL now in canada
2005 C230
1998 C43 AMG Sold to DON
1993 190E 2.6
300TD Former daily driver Totaled
current:
R320 CDI
Ram 2500 Cummins

I don't think so, but it's hard to tell with no tach. It does seem less profound under lighter engine loads

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'95 Geo Metro 3-cyl 5-speed
'97 Geo Metro 3-cyl 5-speed x2
'81 Mercedes 240D 4-speed manual RIP

Mysterious whistle sound has been solved. Today I discovered that the whistle sound was coming out of the muffler exhaust tip. Been a problem for over a year. All this time I thought it might be the turbo wastegate hose or turbo related parts. Vacuum leak was my next guess. Whistle happens between 2k-3k RPM's. Will try to modify the tip. Whistle goes away when placing a rod across the tip.

I had a whistle on an 84 300D that turned out to be one of the EGR hoses. I had blocked off the EGR vacuum line at the EGR, but process of elimination still pointed to the system. Plugged off the EGR system where the vacuum line 'Y's into it near the oil filter canister and the noise went away.

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mjk

'84 300SD 119KMi (Liesl der Diesel)
'84 300D 326KMi when the oil left (former parts car)
'82 300SD 253KMi (new parts car)