Idle a Diesel engine to help protect turbo ? - Bycro
I have been made aware that if you idle a Diesel engine for a few seconds before turning the engine off, it will help protect and possibly add longevity to the life of this component.

Does anyone know if this is correct or a load of rubbish?
Idle a Diesel engine to help protect turbo ? - Cyd

Absolutely correct, 200%

It's even more critical with a petrol turbo where exhaust gas temperatures can reach 1100C compared to about 850C or so for a diesel.

After a good 'thrash' when my (petrol) turbo is glowing a bright orange I have been known to leave the car idling for 15 minutes with the bonnet up. In complete darkness I have noticed it takes up to 10 minutes for the glow to disappear completely.

You'll never get a diesel turbo glowing like that no matter how hard you drive it, but you should idle the motor for up to 2 or 3 minutes depending on how arduous the run was.

There's loads of advice on this subject on here. Have a look in the FAQ section.

Oh, and you should warm the turbo up too. Never drive off the instant an engine fires (any engine, turbo or not). Allow it to idle for at least 10 to 15 seconds before driving off and then do so gently and warm it up before extending power and revs. Idling before driving off allows the pump to get the oil moving, particularly around the cams and other areas which a splash lubricated (cam chain too).

Idle a Diesel engine to help protect turbo ? - unthrottled

Does anyone know if this is correct or a load of rubbish?

Load of rubbish. Diesels pump vast quantities of cold air through the engine on overrun so by the time you come off the motorway slip road and park up at (un)Welcome Break, the turbo and exhaust manifold are plenty cool enough to prevent oil coking in the bearing.

Petrols are a different matter, but the water cooled ones (most are these days) either use turbo timers or natural convection to cool down after switch off.

Idle a Diesel engine to help protect turbo ? - gordonbennet

Driven probably 3 million miles in turbo Diesels, only had one turbo failure and that was fairly recently on a fleet lorry driven by all sorts.

Have always looked after vehicles including warming up and cooling down sufficiently, it pays.

Be interesting to know how many old school lorry drivers, many of whom have owned turbo Diesel cars for years and would use similar care, have had turbo failure? a negligible number i would suggest.

Idle a Diesel engine to help protect turbo ? - RicardoB

Yes, especially if you have come to park up straight after a fast run, or very steep/hard working driving.

And definitely if you're towing a caravan or trailer.

HJ often makes similar recommendations. It's to do with the possibility of the turbo being red or white hot, and if you switch off the engine straight away, the oil in the turbo can carbonise, therefore eventually restricting its flow, eventually causing damage/failure.

Idle a Diesel engine to help protect turbo ? - unthrottled

It's to do with the possibility of the turbo being red or white hot, and if you switch off the engine straight away, the oil in the turbo can carbonise,

A problem that might theoretically occur if you were to switch off immediately after completing the Pike's Peak hill climb.

In reality, the only opportunity to do sustained high speed driving is motorways/dual carriageways. Under what circumstances would you imediately switch the engine off after cruising at 90+mph? Even 90mph cruising is a far cry from the full power dyno runs you see on youtube that cause orange red manifolds.

You see your exit sign, ease off the throttle, roll up the slip road, find a parking space and switch off. All the time your diesel engine is pumping thousands of litres of cold air straight through the exhaust system. You've already done your cool down. By all means sit there for an additional 30 seconds if it provides reassurance

Idle a Diesel engine to help protect turbo ? - unthrottled

a negligible number i would suggest

But would the figure be any different for people who don't have a cool down procedure? I doubt it. If oil coking was a serious problem in turbos then the warranty claims would be horrendous because most turbo diesels start life as company cars where the operators have no interest in the long term durabilty of the car.

Idle a Diesel engine to help protect turbo ? - gordonbennet

No sorry Unthrottled, my previous post was ambiguous, as usual.

I was also referring to the huge mileages old school lorry drivers have clocked up with never a whisper of trouble from their lorry turbos, modern fleet lorries driven by all sorts who don't look after their vehicles in quite the same way do suffer from more regular turbo failure, unheard of even 15 years ago...though i wonder if the move to starship mileage oil change intervals has some bearing (ho ho:-) on the problem, as i'm convinced it has with cars.

Idle a Diesel engine to help protect turbo ? - dieseldogg

A cousin of mine who worked to a quarry owning uncle in Austrailia back in the eighties, asked Uncle Alf why the trucks were left running during tea and lunch breaks.

Alf lifted the bonnet of the next truck that pulled in, and according to cousin Allen, he could see the turbo glowing cherry red.

marcus

Idle a Diesel engine to help protect turbo ? - Sofa Spud

I'm aware that it's beneficial to let a turbocharged engine idle for a while (I leave it about half a minute) before turning off), but isn't good practice to do this with all engines?

Edited by Sofa Spud on 22/06/2013 at 18:59

Idle a Diesel engine to help protect turbo ? - unthrottled

I only allow extra idling time if I've stopped immediately after climbing a steep hill, the concern being that the hot manifold might overheat the cylinder head. I still think this is being over cautious though!

Quarry lorries are running at rated output whilst moving at 5mph, passenger cars don't!

Idle a Diesel engine to help protect turbo ? - Ernied

Going back to the 70's I can remember de-coking an even older 6 cyl petrol engined Bedford coach. Job finished, decent test run, back to the workshop and lifted the engine cowling (inside the bus) and in the semi darkness the exhaust manifold glowing red hot. It was getting late, so checked a few things, ign timing etc and called the main dealer next day.

Oh yeah - normal, they all do that. And that was after a leisurely unloaded test run.

Idle a Diesel engine to help protect turbo ? - unthrottled

Going back to the 70's I can remember de-coking an even older 6 cyl petrol engined Bedford coach.

That's why you don't see many petrols in buses and trucks! Rich burn gas engines usually need a water cooled exhaust manifold to protect the turbine. Or just use a diesel...

Idle a Diesel engine to help protect turbo ? - galileo

The company I worked for made turbo's for automotive diesels with watercooled bearing housings and for marine engines, watercooled turbine housings.

For some high duty marine applications, instead of watercooling the turbine housing an insulating jacket was fitted for better thermal efficiency.

Idle a Diesel engine to help protect turbo ? - 1litregolfeater

Somebody must have told the taxi drivers round here, they never turn their engines off.

It's an absolutely correct idea, but it just depends how hot it is, so most of the time, it doesn't matter.

There is a stress to a lot of expensive components every time you start a diesel engine. Starter motors don't last and batteries at £90 a pop deserve looking after.

Idle a Diesel engine to help protect turbo ? - brum

There is a stress to a lot of expensive components every time you start a diesel engine. Starter motors don't last and batteries at £90 a pop deserve looking after.

Hmmm......Most manufacturers are fitting automatic stop/start on their engines to reduce CO2 emissions

Idle a Diesel engine to help protect turbo ? - gordonbennet

Hmmm......Most manufacturers are fitting automatic stop/start on their engines to reduce CO2 emissions

Yes and it will be interesting to see how many owners of such once out of warranty start receiving 4 figure bills to replace starter motors and alternators, i suspect the few pounds saved by autostop over the years will pail into insignificance when the hardware bills arrive...i expect the stop start functions will be permanently disconnected at the same time.

Something else i won't be buying into.

Idle a Diesel engine to help protect turbo ? - Andy P

Depends on the design of the turbo. This is from Garrett's website:

Q. Should I run a Turbo Timer? A. A turbo timer enables the engine to run at idle for a specified time after the ignition has been turned off. The purpose is to allow the turbo to cool down thus avoiding "coking" ("coking" is burned oil that deposits on surfaces and can lead to blocked passages). The need for a turbo timer depends on how hard the turbo and engine is used. Running at full speed and full load then immediately shutting down (heat soak) can be extremely hard on a turbo. Water-cooling of the turbocharger's center housing has essentially eliminated the need for turbo timers or extended idling periods.
Idle a Diesel engine to help protect turbo ? - Bromptonaut

The handbook for my HDi 110 Xantia reccomends letting it idle after sustained high speed running. I'm not sure UK or even French Autoroute speeds (even at 85 it's under 3k/rpm) really meet that description. Less so by the time you've driven into services etc and stopped.

Climbing a mountain pass on the other hand......

Certainly let it idle for few minutes after going up Alpe d'Huez or similar.

Idle a Diesel engine to help protect turbo ? - Collos25

I had to let my heart idle when I rode the Alpe d´Huez last year.

Idle a Diesel engine to help protect turbo ? - Bromptonaut

I had to let my heart idle when I rode the Alpe d´Huez last year.

Chapeau!!

Idle a Diesel engine to help protect turbo ? - mike hannon
The handbook for our 2010 Honda Accord - our first (and maybe last) diesel car - recommends idling the engine for 10 seconds before switching off after hot running.
 

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