noise after turning off E320cdi

My yr 2000 E320cdi continues to sound like a jet engine after I turn it off. This goes on for quite a time i.e. several minutes.
It is not as loud as an rb211 jet (obviously) but has the same kind of
spectrum.
I should be more analytical but it seems to happen more after short journeys than long journeys where the car is really warmed up. It also starts loudest and then gets a bit quieter.
I have no idea what the noise is.
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nihil ha scritto:

Most probably the cooling system is still on, when you switch engine off. First, I'd check carefully the level of coolant. Not only in the plastic bowl, but also in the radiator: sometimes the cap of the radiator stops opening correctly.
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When I had an E320CDI I thought the heater water circulation pump would be running a while after the engine was switched off but it isn't. If this noise s something similar, more continuous than from the cooling system or AC, I believe it is one vacuum controlled flap that keeps going until vacuum is lost. An MB workshop expert explained me where this noise comes from but I really cannot remember the exact part any more. Totally harmless if it is the same.
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Anonymous wrote:

a 12 mile journey (there is no radiator cap). At the end of it I turned the engine off and there was no noise.
However, when I returned home a few house later and when it was significantly colder, the noise continued after turning the engine off. The noise comes from the front right hand side of the engine bay (same side as the turbo). I don't know if this is where the heater water pump is situated.
The difference between the two journeys was the outside temperature. Is it possible that the catalytic water heater was activated on the colder return journey but not on the warmer outward journey and that the noise, as you say, is the heater water circulation pump? It stopped after about 4 minutes.
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Replace that coolant safety cap.
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After switching on the engine, the fuel pressure in the fuel rail (across the fuel injectors) should normally still stay high. If either the pressure regulator valve or a check in the pump system is not shutting off completely, it could give such type of noise (decreasing as pressure slowly drops).
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Of course I mean off...
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Jens wrote:

flap by the ashtray) the noise doesn't happen.
If it is cold even after a long journey this heater is activated. It is supposed to turn off when the engine reaches operating temperature. However there is a fault in either the thermostat or the temperature sensor such that the recorded temperature is never more than about 65 degrees Centigrade. The low reading is probably causing the heater to remain on.
Now I now I just switch it off when the engine has warmed up.
I do not know whether to spend 40 to replace the thermostat and temperature sensor (which are all in one unit). I have heard reports that these cdi engines run cold anyway and that the temperature sensor under-reads.
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I have a C270CDI and it does the same, a rumbling/rotating noise for a few minutes after shut-down from somewhere in behind the trubo area, and runs cool per its own temp gauge. I'll try switching off the heater as you suggest to see if it makes any difference.
John in Ireland

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