SPINNING DOWN FAN NOISE AFTER SHUTOFF

[bsamot69]

Our m9540d is running normal. Recently, I have noticed when I shut tractor off, I hear what sounds like a fan spinning down when you take power away. I have isolated it to the area of the turbo.
This is a new sound and there is no apparent new noise when running tractor. Shut it off and you can hear the spinning as it winds down. Anybody have issues with the turbo? Should i prepare to replace it? or is there some other remedy. don't hear much about turbo issues. Any advice or insight is greatly appreciated

 

[Dave_eng]

Our m9540d is running normal. Recently, I have noticed when I shut tractor off, I hear what sounds like a fan spinning down when you take power away. I have isolated it to the area of the turbo.
This is a new sound and there is no apparent new noise when running tractor. Shut it off and you can hear the spinning as it winds down. Anybody have issues with the turbo? Should i prepare to replace it? or is there some other remedy. don't hear much about turbo issues. Any advice or insight is greatly appreciated

Tell me about your engine shutdown steps.

If the engine has been working do you give it a couple pf minutes to cool down and for the turbo,, which is spinning at up to 30 to 40,0000 rpms. or more to slow down before turning the key to OFF?

The turbo's two internal impellers, both locked together, one in the intake and one in the exhaust have no direct mechanical connection with the engines moving parts. When the engine stops the turbo can still have inertia which keeps it spinning for a little while.

In the early days of turbos, owners who abruptly shut their engines down often suffered turbo bearing issues because the continued spinning of the impellers in the absence of lubrication of their bearings from the engine oil system caused failures.

Designers of turbo's today utilize much better bearings but the inertia of the impellers means they will not stop immediately.

I believe what you are hearing to be normal. However, changes in sounds when the operating procedures are unchanged needs to be monitored.

Dave

 

[lugbolt]

normal

the turbocharger shaft, compressor and turbine wheels are all connected together, and at idle speed that shaft assembly with the two wheels is turning about 50,000 rpm. It has inertia. When you turn the engine off the inertia of the assembly keeps it spinning for a bit until it finally stops

most people don't hear it but it is audible if you listen for it

if it's kinda loud and unmistakeable, possibility exists for an exhaust or intake tubing leak, and for those I would look closely at the intake hoses for sure, as well as the little discharge hose that runs from the turbo to the intake manifold, seen a couple of those develop cracks and the usual complaint is abnormal noise. Look at the hoses closely from the turbocharger compressor inlet all the way to the air filter, and make sure everything's properly seated and all clamps are tight, and the air filter is in good condition. Beyond any leaks, without hearing it in person I couldnt' say whether the turbocharger is beginning to die or not, but that would be extremely rare...UNLESS it's ingested dirt or other foreign matter, OR it's lacking (or has lacked in the past) good clean pressurized oil. Generally when a turbo fails, it's obvious. One thing I usually do if it's even suspect is to pull the hose off of the compressor inlet and look inside at the compressor wheel with a flashlight. If the tips of the blades are worn off or otherwise damaged, a replacement is likely in order--and that may not solve the owner's problems, as generally if dust gets in there, the engine is also dusted and may or may not last long

both of my cars and my truck are all turbocharged, the little 4 cylinder in the car has 3" exhaust with no catalytic converter, and a really loud turbine side of the turbo so you can hear it a mile away (not by choice--it's just normal for that turbo), shut it off at idle and it's spinning up to 20 seconds after the engine is off (and audible). THe truck will keep spinning up to a minute, but you have to listen close to hear it (7.3, stock exhaust). Turbo's quite a bit bigger'n the one on the car which is tiny in comparison

 

[bsamot69]

Thank you for the things to look at and insight on turbos. As far as shutdown, after working out in the field, it is a leisure 10-15 minute drive to the equipment shed. Pull in and idle for half a minute then turn off.

 

[dvcochran]

FWIW, I hear the turbo on my M9000 much more when it is good and warmed up.