ML 270 sounds like a police siren

[nhw]

The engine on my ML 270 makes a sound like a police siren. My local dealer thought the turbo might be cracked. I can't find a crack. Is this a common problem?

 

[rpe2]

The engine on my ML 270 makes a sound like a police siren. My local dealer thought the turbo might be cracked. I can't find a crack. Is this a common problem?

If you take it to your dealer or specialist they should be able to pinpoint the noise. I would wager a holed intercooler/ turbo hose (assuming that you are also experiencing a loss of power under load).

 

[Cosworth]

The large coolant radiator fan can cause this type of sound

 

[stumo]

My turbo (in 02 ML270) makes this noise too. In my case it is only when the engine is cold and only when spooling up/down, not at full power, it also goes away when engine is warmed up, so the diagnosis in my case is slightly worn turbo bearings.

When they get a bit worn, the cold engine oil in the turbo bearing clearnaces causes a police siren noise when it is spinning up/down (ie. releatively low turbo speeds). The bearings aren't ao badly worn that a rebuild is necessary, so it is a case of just living with it. It has gotten a tad quieter since a recent oil change to mobil1 0w-40.

Your case could be entirely different and a leak can cause a similar noise, but I just thought I'd throw this out there if you were trying to narrow it down a bit.