Should I hear the turbo spool down at shutdown

[Boreal]

I have a CAT 252b3 with the turbo 3.4. In the warmer months I hear the turbo spool down when shutting down but now in the colder temps I don't hear it.

My shutdown procedure is pretty consistent. I let it idle for a few minutes then shut her off. And I don't notice any lack of power so I assume the turbos working. But I do miss the cool turbo sound when climbing out of the cab. Just wondering if that's normal.

 

[Nige]

Are you sure that the noise you can hear when shutting down isn’t the fan.? It’s demand driven so in summer it will be spinning pretty fast and in winter hardly turning at all.

 

[Boreal]

Are you sure that the noise you can hear when shutting down isn’t the fan.? It’s demand driven so in summer it will be spinning pretty fast and in winter hardly turning at all.

I guess I'm not sure. I always just assumed it was the turbo because of the spooling sound. The fan would make more sense but that would be an impressive fan noise.

 

[Nige]

The fan would make more sense but that would be an impressive fan noise.

When you think about noise consider the diameter of the fan assembly compared to the diameter of the guts of the turbo. On this type of hydraulically-driven fan most of the noise is actually the drive motor spooling down. Stand next to the back of the machine with the door open and have someone switch off the engine.