(85 300SD, 294k)
Vacuum whistle coming from vacuum line that goes into the turbo. Some sort of bypas diaphram. Only "whistles" at cruise. Accel or Decel = no whistle. Very loud at 60+ mph. I've stopped it by pluging that line. I've looked for a rebuild kit or a new diaphram but can't find one. Only started this after about 200k or so. I've been running with that line plugged ever since. Doesn't seem to effect performance that I can tell.

I've just found this site. (I go to one similar for my 96 GMC 6.5 diesel.) Has anyone had a similar situation? I'd rather get this fixed, but no one can find a part number for a replacement diaphram, (other than replace or rebuild the whole turbo).

Thanks...

unhook the line and plug the vacuum line and the whistlle will go away.

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Jim

In 1984-1985 Mercedes had an issue with the EGR valves wistling at only certain RPM ranges. There was a bullitin that was put out that showed how to drill a hole in the valve to get rid of the turbulence that was causing the whistling. Could your issue be related to this. My 84 300d does it and I have been told that it does not cause any issue. It only whistles at part throttle around 2000-2500 rpm.

DieselNation

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82 240D - 257k
84 300d - 86k

EGR Valve? I could try it.

All I know is that with the vacuum line to the turbo pluged, there's no whistle.

Where can I find out about that bulletin?

It does not hurt anything to whistle.

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Jim

Captaincrunch,

There was a service bulliten sent to the dealers from Mercedes. I would imagine that only the most experienced technicians would know about it.

Ducati,

From what I understand is the only reason that it was modified was for the people who bought a brand new $32,000 Mercedes and were complaining that it whistled. The single reason for the modification is to get rid of the noise.....no impact on performance. I kind of like to hear the whistle so I will keep mine the way it left the factory.

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82 240D - 257k
84 300d - 86k

Do I feel like a goof. I have the same noise at about 2000 to 2500 rpm, & I thought it was turbo whine.
D'oh...
It does not seem to be causing any problems, however as I have already demonstrated ignorance, perhaps I should ask - is that whistle indicative of a problem present, or trouble looming later?

No, no. This is an annoying whistle. Loud enough to hear inside. Can't ride with the sunroof open.

Anyway. Has anyone ever replaced that diaphram? All I know is that it didn't whistle, then it does. The only changeable component is the diaphram. I'd like to replace it.

I was told that the diaphram has something to do with turbo back-pressure or something.

Hello, thanks to all on this forum for making it what it is. I have saved immeasurable amounts in both money and time in the assistance you have all provided in your posts. One thing that has eluded me for the past year with no resolve until a few days ago was the darn clunking that seemingly came from the rear end whenever shifting up or down under light load. My car has 157k, is a 1985 300d turbo Californina model and i figured that all the stuff I replaced to chase down this clunking would benefit the car even if it didn't fix the clunks. The problem, just as many had already pointed out, was vacuum. My initial ignorance about Mercedes vacuum systems and poor troubleshooting strategy has tought me several things. First, the reason I bought this car was to save money and enjoy a first class car from a build standpoint. But, I feel obsessed with making everything work properly and even after I change the oil I almost feel an itch to change it again after a week, but resist until 2-3k (I bought DELO 400 from Walmart for 1.08 a qt). I learned most importantly that I need to troubleshoot by learning the system more thouroughly, i.e. - I need to buy the dang manuals and read them as opposed to doing everything from my supposed all-encompassing mechanical ability (I thought). I wound up learning backwards the entire vacuum system only to find the culprit being at the end of my learning journey. The Californina model I have has a diaphram in the turbo in addition to the wastegate that controls boost. The diaphram had developed a small leak and caused an intermittant vacuum problem affecting everything, but most significantly the shifting. While I have been unable to find a replaceable diaphram (anyone have any ideas?) I simply disconnected and plugged the vacuum hose leading to the offending part. The first clue for me shoule have been when I hooked the mighty vac up to the tube going to the tranny modulator and assessed the vacuum dropoff that occurred (most of the time) and gone backwards from there. The reason why i strayed is that the clunk seemed far too significat to be caused by vacuum, like it was eminating from the rear end, but happily it was not from there. I will stop writing there, as I, like all of you, can write novels about our adventures with hese cars when our wives are telling us diner is ready and we say, "just a minute" and come in only after we are threatened. Once again, thanks to all of you for your guidance. Adam Bush

My car has this 'whistle' also. I've asked about it before here but no one seem to know for sure what it is.

I've since come across this TSB that seems like it may be what we're all hearing.

Oh...and Adam, just a bit of advice. Posting in one BIG paragraph makes for an annoying read. Breaks up your thoughts my good man :p

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Chris
1985 300SD - 'Grace' (198K mi.)
2018 Honda Civic Sport
2018 Honda CRV LX
2010 Honda Fit Sport (RIP)
2013 Honda Accord Sport (Sold)
1996 Lexus LS400 (Retired)
1995 Ford Contour SE (Retired)
1976 Porsche 914 (Sold)
1972 Datsun 240Z (RIP)

Well what the heck!

My 85 300CD whistles too...in the lower vacuum transition between acc/deceleration...I have been hunting for the offending noise, but as yet unable to locate...to me is sounds like it originates somewhere under the car...any ideas about that? What's under there that COULD whistle?

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...a man's gotta understand
his limitations...

83 300D 360 K (Big Blue)
85 300CD 250 K (Little Blue)

Look at my post above and click the link to read the TSB. Not saying that this IS what you're hearing but it could be.

Chris

hi captaincrunch:
In nutshell, EGR is a Diesel engine killer. It will not hurt to completely bypass the EGR valve. This can be done by inserting a ball-bearing or a rubber plug into the rubber connector at the EGR valve. This will also improve the performance and mileage on the car.

The other valve is an Air-recitculating valve which sits on turbo unit. That too can be blocked esp for cars that have no cat converter or trap oxidizer. It does not affect the function of turbo but will give you a slightly enhanced performance and also a bit smoother shifts without clunck. This valve can be blocked the same way as EGR. This valve also is the culprit resulting in surges while the car is on cruise control.

A slight whistle is typical of all turbines or turbo. and that noise should not be confused with excessive whistling due to ARV.

Hope this helps.

MVK

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One penny saved is three penny earned.

1985 300D Turbo 179,000miles

My 85 200SD also has "the whistle". I first noticed it right after I bought the car 12 years ago. Guess it doesn't hurt anything.

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Current Vehicles:
1990 Mercedes 300SE (147,000)
1985 Mercedes 300SD (203,000)
1983 Mercedes 240D (167,000)

MKV,

I tried plugging (85 300CD)what I think is the EGR line...i.e. the tube that connects from the top of the valve cover to the top of the air breather/filter (large flat) assembly...the engine will not run with those lines pluged...stalls after only ten of fifteen seconds...I must be plugging the wrong line (yes I have unplugged it now)...can we post pictures with our questions in this news-group? That would sure make some of these discussions simpler...I have to get back to my Chilton's (which is poorly written)to try to identify the correct line.

Mike

__________________
...a man's gotta understand
his limitations...

83 300D 360 K (Big Blue)
85 300CD 250 K (Little Blue)