turbo wind down noise after engine stops on shut off

on our Mack E7 upon shutdown as soon as the engine totally stops, then there's an winddown noise that sounds exactly like a starter winding down from full speed to a stop. It takes several seconds for the noise to stop. We haven't had this truck very long and it's done it everytime on shutdown. For a while I was afraid maybe the starter was stuck engaged, but that would burn up the starter very quickly so it's not that. It has got to be the turbo winding down but i've never heard one this loud. On our 6NZ C15's, we notice no turbo wind down noise on them, so why is there on this E7? Is the turbo on it's way out? It's a non-wastegate turbo if that matters. We don't have a boost gauge on the truck, so no idea how much boost it's producing but the turbo does still work. You can hear it spool up when pulling a hill and accelerating.I'm just concerned about the wind down noise. Should I be concerned?

 

are you shutting down the engine as soon as you stop, or are you letting it idle down for a bit for the oil to continue to circulate thru the turbo bearings?

 

The only thing we have ever been taught is to idle 5 minutes to cool turbo. Then shut it off normally if that is the plan.

My hearing is not that good that high up so it will have to be in some real distress for me to hear it. otherwise I just run it normally. And yes I do resent the constant removal of relevant gauges from inside the big truck. Used to have dozens of them for every little thing.

 

By the time I get it backed into it's spot, then i have slowly moved it around the yard to dump the load, etc and once i park it, i sit for about 30 seconds at idle before shutting down. I'm just concerned as to how loud the turbo sounds as it's slowing down to a stop once the engine shuts down.

 

30 seconds idle down time, may not be enough. that turbo is still spinning fast.

i never gave my trucks less than 1-2 minutes of idle down time, in all my years, sometimes a bit more, as i did a quick line on the logbook, or get my bills.

 

it still makes the exact same noise if i dont shut it down and the idle timer shuts it down....

 

VGT turbos are noisy. I'll bet your making 6psi boost at idle.
But your engine is a Volvo so I do not know much.

My old 12.7 trout egr made 6psi at 900 idle.

 

It can be normal for some engines that a turbo will spin after shutdown for a moment.

 

It's a Mack engine (E7) and it isn't a VGT turbo. it's a plain jane, run of the mill normal turbo. there are no electrical connections anywhere on it and no wastegate.

 

Apologies I thought I read MP7.