One thing I noticed right away about our XE was that after shutting off the engine I could hear a small pump running. Presumably, the pump is circulating either oil or coolant to the turbo - never checked to see what it does. I realized the other day after shutting the car off that I did not hear the pump running. I checked again a couple of times and, even after longer trips, still no pump noise emanating from under the hood. Our weather is now much cooler in PA, so not sure if the after cooler function is connected to outside air temp or what the scoop is. Anyone?

 

My 35T hums quietly to its self, as did my previous MB, for about 10 mins after shutdown. (The dealer said its 10 mins+-, I never waited to find out) It's the cooling fan for the computer/infotainment system. I don't recall it being affected by the outside temperature though.

 

Thank you for the reply, but I am fairly certain that this noise is an electric pump running under the hood and not in the dash. I do hear a low hum from the dash area and that must be the fan for the electronics.

 

I think what you are hearing is the electric fan for the radiator, which is controlled by a thermostat.

 

Hmm. Easy enough to check that, but the noise is a low and steady drone rather than the whir of a fan.

 

Our temperatures came up a bit in our region and the noise of a pump running has now returned upon shutdown.