Idle the turbo before turning off engine (1 Viewer)

Fulltiming Felines

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How long should I idle before turning off the engine to allow the turbo to cool off? For example, after a few hours motorway driving then stopping for fuel.

I have a 1991 Hymer 534 Fiat Ducato 280 1.9 Turbo Diesel but I'm imagine it applies to most turbos.
 

Geo

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The story goes like this
When the engine is switched off the oil feed to turbo is also cut off
if you switch of immediately your turbo could be spinning for 10 to 20 seconds without oil
instead it is suggested when stopping idle for 30 seconds to allow turbo to slow down then switch off
thereby lessening the amount of time the Turbo runs with less lubrication

You either Do or you Dont
 
Oct 29, 2016
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Totally agree with @Geo, oil starvation is the biggest cause of turbo bearing failure, easy to understand when you consider the RPM of turbo fan blades.
Leaving the engine to idle for a while before turning off, allowing the turbo to stop spooling can only be good advice, harder to remember to do it if that concept is new to you, but can only be a good practice in the long run.
Turbos are expensive items to replace on any vehicle petrol or diesel.
Les
 

Allanm

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I thought you only needed to allow the turbo to cool down after it’s been working hard, eg, climbing a hill or fast motorway speeds, a few minutes of normal driving after such events should cool it down enough to turn the engine off straight away. Letting it run for a short while will do no harm, I suppose you do what you feel comfortable with.
Turbo development has come a long way since I had a 1987 Mitsubishi Pajero, it was fitted with a Turbo Timer that ran the engine for a while after you turned the ignition off. It was fully automatic and the running time depended on how hard the turbo had been working before you shut the engine off.
It only ever ran on more than a few seconds once, after I had towed a forklift truck off a muddy field!

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Geo

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I thought you only needed to allow the turbo to cool down after it’s been working hard, eg, climbing a hill or fast motorway speeds, a few minutes of normal driving after such events should cool it down enough to turn the engine off straight away. Letting it run for a short while will do no harm, I suppose you do what you feel comfortable with.
Turbo development has come a long way since I had a 1987 Mitsubishi Pajero, it was fitted with a Turbo Timer that ran the engine for a while after you turned the ignition off. It was fully automatic and the running time depended on how hard the turbo had been working before you shut the engine off.
It only ever ran on more than a few seconds once, after I had towed a forklift truck off a muddy field!
Simply to preserve the oil supply to the bearings, temp has little to do with it
 
Oct 29, 2016
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Letting the engine Idle for while is a good belt & braces habit to get into. When you see how hot a turbo gets on a run,you can understand why the cooling fans run on for a few minutes, sometimes.
Lift the bonnet in the dark and you will probably see the whole turbo body glowing red with heat.
We just traded our much loved Audi Q3 4x4 diesel turbo, it was sometimes amazing how long the cooling fans would run after the engine was switched off, even on a fairly short round town drive.
So I will continue to let the engine idle for a short while after all types of run, as it can only be a good thing.
Les
 

Jim

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My handbook says

On E-Series vehicles, to prolong engine life (after extended high speed or maximum GVW operation), it is recommended that a hot engine be
idled for 7–10 minutes which will allow the turbocharged engine to cool down.
 
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Mine had stickers on the door card & sunshade .idle for 2 minutes before switching off.
That would be great when trying to fill up at a motorway services. :cool:

It is also recommended that when you are arriving at journeys end you drive the last few miles "off turbo" I.e. not actually using it so allowing it to cool.
My van hasn't a turbo but I never switch that off for at least 2 minutes & never if the engine fans are running until they have stopped.

It's very rare that whilst in the Uk I never had to queue for at least 5 minutes to fill up.
 

pappajohn

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Mine had stickers on the door card & sunshade .idle for 2 minutes before switching off.
And then they developed auto stop start for temporary holdups to reduce emissions.
So do you follow their advice or do you use their inbuilt technology.
They don't seem to know what to do.
'they' being the manufacturer.
 

Geo

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Not enough to worry about though or there would be cracked blocks and blown head gaskets in every street.
There are, ive seen a good few blow their stack after switching off after running ok
a sensible Mechanic wont stick his head in for a minuet or two
 
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A friend of mine had a Suzuki Cappuccino that was a turbo-charged motorcycle engined small sports car.

After switching off the ignition the engine would idle for a few minutes so as to cool down. Odd to see people's reactions as we walked away from it after locking up and the engine still running
 

ambulancekidd

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Ambulances are often abused in the very way that they shouldn't be. ie; Arriving on scene & switching off immediately. To this end all ambulances have a carousel system whereby a one touch button puts the engine to idle & turns on the rear interior lights etc.
You can manually turn on or off the blue lights etc for safety but, crucially the vehicle cannot be stolen as the crew will have the keys in their pocket & its even possible to activate the central locking to leave the vehicle safe & secure.


Arriving at a motorway service station isn't usually an issue for the turbo as the few minutes it takes to get to the car park or filling station allows the turbo to spool down anyway.
As has been stated here, its not heat that's the issue, its the turbo doing extremely high speed when the oil supply is suddenly shut off.
 
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That says the turbocharged ENGINE Jim, not the turbocharger.
Though why you would need to wait for the engine to cool is a mystery.
If there's NO heat source, IE: combustion, it will cool even faster

Can't believe that a mechanic has posted that!

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Fulltiming Felines

Fulltiming Felines

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Arriving at a motorway service station isn't usually an issue for the turbo as the few minutes it takes to get to the car park or filling station allows the turbo to spool down anyway.
Yes, usually, but sometimes there's a fuel station right off the motorway where you can go from 60 mph to zero in a minute. So I figure idling for 5 minutes would be worthwhile then.
 

Jim

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That says the turbocharged ENGINE Jim, not the turbocharger.
Though why you would need to wait for the engine to cool is a mystery.
If there's NO heat source, IE: combustion, it will cool even faster

Clearly they want the oil to circulate and cool it. Something it cant do when it's off.
 

mfw

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Engine temp can increase above normal temp especially in hot weather or traffic jam engine and cooling system working hard so probably better to let temp get back into normal area before turning off engine unless a cooling hose goes.

Normal circumstances the turbo probably gets an easy life especially in a motorhome

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Allanm

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Simply to preserve the oil supply to the bearings, temp has little to do with it
I think, and so do turbo manufactures, that temperature has all to do with it.
This is from HKS, they make turbos so should know what they are talking about

“The number one cause of turbo failure is oil "coking". Oil "coking" occurs when a turbocharger is not properly cooled down and the oil that normally lubricates the center cartridge heats up and forms solidified oil deposits."

My Pajero handbook said the turbo timer operates to allow the turbo to cool down after labouring. There would be no point letting the engine run on for a few minutes to preserve the oil supply because when ever you turn the engine off, the oil supply is cut.
I should imagine the turbo will spool down in a few seconds not minutes so letting the engine run for 5 minutes after stopping would achieve nothing.
 

Louis

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Yes, usually, but sometimes there's a fuel station right off the motorway where you can go from 60 mph to zero in a minute. So I figure idling for 5 minutes would be worthwhile then.
Not off a motorway there isn’t? Only off expressway or dual carriageway (y)
 

Chipster

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I will let a vehicle idle for a bit before turning off. What about stop/start systems now very prevalent in cars? Both our vehicles have it, both are turbo charged.. Although I do tend to disable it.

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