For the last week, I've been hearing a strong hiss coming from up front upon acceleration. It seems to coincide with the turbo spooling up. Today, I found that the hose which I believe to be the one going from the wastegate actuator over to the top of the turbo is severed and hanging there. Am I correct that this is the source of the noise?

Must I replace this hose immediately or is it okay until the next service (in a week or two)? Doesn't look like a big deal to change.
Is there a specific part that I need to pick up for this?
Thank you in advance!

That is probably the wastegate line that is leaking. By venting charge air to the outside, your wastegate is not functioning properly at high boost and you may be overboosting the engine.

Not good. Fix now.

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Never a dull moment at Berry Hill Farm.

my car does sort of the same thing...i hear the turbo spool up good under acceleration,but i hear kind of a whoosh sound,similar to that of a blow-off valve,when i let off the pedal....is that normal? i always guessed it was the wastegate relieving boost pressure from the heavy acceleration....and i know its not over boosting,since i have a boost gauge installed in the car,and it reads 11psi max at full load....my car has also made this hissing sound way before i upped the boost on it,too...even when it was at only 7psi of boost.....

but i do know its not good to have a leaking,or disconnected wastegate hose....since,(correct me if im wrong) thats what tells the wastegate when to cut off boost pressure...if that undone,it would make sense that your turbo is putting out wayy too much pressure....

the hissing,im curious about....

Is it true that you can hear the turbo "spool up". I've had my 300D since March and I swear I can't hear it do that. I'm sure it works because I can feel a real surge in power as the engine revs higher. Maybe I don't know what to listen for. Is it real subtle?

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DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012

yeah,its pretty subtle....i only heard mine really well because i was using an aftermarket air intake,which i recently took off because it was too loud for my liking...but with the stock air cleaner on there,its pretty tough to be able to hear it above the diesel engine

85drtysthbenz------Did you ever figure out what that sound was? Sounds just like what mine is doing.

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RT


1984 300D---Sold
1995 E420 - 106K - Brilliant Silver Metallic/Orion Gray --- Sold
1984 300SD - 151K Manganese Brown Metallic/Mostly Black --- Sold
1982 240D - 79K - Manila Beige/Palomino---Sold

RT,
i still dont know for sure what the sound is...my guess would be that its the wastegate relieving excess boost pressure when the car shifts gears...thats really the only time i hear the whoosh sound....it sounds as if theres a blow-off valve on it....i cant say for sure though

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1985 300SD 192,000miles...Astral silver/ Grey MbTex

1983 300D 194,000miles...White/Tan MbTex...my newest addiction

The wastegate doesn't relieve pressure -- it controls the amount of exhaust going through the turbine and "wastes" exhaust around it when boost pressure reaches the correct level. Much quieter than blowing the pressure off the intake side, to say nothing of saving the air filter.

Look closely at the intake to the turbo. I'd suspect the intake hose is loose and partially off -- you have an air recirc valve, I think -- a variation of the blow-off system -- that vents compressed air off the intake and back in front of the turbo. Two reasons for this -- used to help protect the trap oxidizer and it tends to keep the turbo up to speed longer, so there is less throttle lag at medium speeds in traffic. You normally don't hear it, but if the intake pipe is loose, you get a moan or whoosh when the valve opens. This happened on my bother's 300 SDL.

Ordinarily, you won't hear the turbo on a Benz. On my Volvo TD, it sounds as if there is a cop car about a block behind you.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

If it sounds like leaves blowing and only under acceleration, and then levels off/disappears when you maintain speed it is the overboost hose. Just had the same thing happen to mine. New hose = no more noise.

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1982 Mercedes-Benz 300CD
1982 Mercedes-Benz 240D - stick

You can really hear the turbo spool if you have the lower panel off (by blower fan) in the interior or even glove box apart. I was amazed by the difference, I never would have thought I was spooling or boosting going 60mph. I have my K&N on order right now, supposed to be in monday.

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Jeff M.
Mercedes W123 DIY pages are now located here.
1983 / 1984 300D Sold
2000 CLK430 Cabriolet ~58k Sold
2005 Avalanche 4x4 ~66k