Nissan X Trail

[colin(bridgend)]

A reply in today's motoring section of the Daily Telegraph refers to the life of the turbo fitted to the X Trail. It was advised that when running hot for some time either by towing or by high speed that the car should be allowed to idle for 2 minutes to allow the turbo to cool. By doing this it apparantly extends the working life of the turbo. I have not heard this advice before and does it hold good for all turbo engined vehicles. I have owned a Daihatsu Fourtrack TDI for almost seven years and have never experienced any problem with the turbo and turn the engine off without the pause for cooling down the turbo. Here I go now, Col's Law (taken over from Sod) my turbo will now go.

Any advice/comments about this reply in the paper.

 

[S_374382905]

The short answer is no. The X Trail version concerned was prone to this problem.

I have had turbo diesel cars of various makes for years and have never had any problems at all. Indeed, if I had to pull up at a garage to fill it up but have to wait two minutes 'on idle' before I stopped the engine, I would be seriously 'miffed' - not to mention the other people queuing behind me!

I think the X Trail is a great car- but would only buy one of the models where this problem has been sorted out - e.g the latest one,

 

[jacky3]

hi,

i have an x-trail,not got the manual near at hand but i'm almost certain it advises this in the handbook,and yes it has been advised to me by other people.

 

[jacky3]

hi,

i have an x-trail,not got the manual near at hand but i'm almost certain it advises this in the handbook,and yes it has been advised to me by other people.

sorry i should have said for the turbo to actually slow down,you shouldnt turn the engine off immediately after a long run or strenuous activity like pulling a caravan,you supposed to let it slow right down

 

[xtrailman]

The consensus of opinion from the honest john web site, is to idle the turbo, petrol or diesel, especially after a long run.

apparently the latest VAG cars mention this in the manual.

The theory is to allow the oil to flow through the turbo bearings, so allowing the turbo to spool down under lubrication.

Its always been my practice with any engine after a long run especially, to idle the engine for a couple of minuets, with everything turned of, this allows engine lubrication, and provides a charge to the battery.

The xtrail from 2004-2006 had a few turbo failures, due mainly to faulty boost pressure sensors, also ECU's were sometimes given a remap.

My 2004 xtrail is now on 35k, with no turbo failure,(my son owns it now), all my car had was a new boost sensor fitted on recall.

 

[Gafferbill]

...... this advice has been recommended for many years for oiled cooled turbochargers.

However it only applies when the turbo is very hot after the engine has been pulling hard and the requirement arises to stop the engine.

In this situation a minute on idle will save the oil in the turbo from cooking and destroying the turbo's oil seals.

Best practice is to drive with sympathy to the engine just before you are about to stop it.

 

[ChrisUK]

My Mazda 6 diesel owners manual told me to do this, I now have the latest Xtrail (T31) and it doesn't, but I do anyway! The Nissan manual actually tells you to wait 30 sec before driving off when first starting to get the lubricants flowing. If after a run you turn the x trail off and listen very carefully you can hear a low buzzing sound from the engine which on the X trail forum was explained as a small electric coolent pump to cool the turbo down. Looking at the workshop manual I can see this is true.

going back to the question, think about coming off the motorway into a service area, you go from high load to switching off in only a few minutes, the turbo which is probably at over 1000 deg will then disapate this heat into the stationary oil in the bearings, which it won't like. So keep the engine running for at least 30 sec. This applies to all turbo cars including petrol.

I have seen on the forums where people have used devices to keep the oil flowing after the engine is switched off but this is going to far.

If I'm driving say around town and stop I don't bother, you just have to think about the state of the engine. So people won't buy a second hand turbo car incase the previous owner has'nt bothered.

 

[xtrailman]

Chris

Two questions.

1/ what xtrail forum do you use, the yahoo?

2/ where did you get the workshop manuel from?

I once went into my local electrical supplier and noticed a subaru impresser turbo, with the engine running, thinking the lad had forget to switch off i mentioned it to him, oh it does that, i've switched it off, but the engine management runs the engine to cool the turbo.

 

[seth1]

Colin,wouldnt worry to much about turbo failure on the old faithfull the majority of them, infact all independants i.e

fitted with DL52,S had watercooled turbos as well as obviously being pressure fed with oil.

 

[ChrisUK]

Chris

Two questions.

1/ what xtrail forum do you use, the yahoo?

2/ where did you get the workshop manuel from?

I once went into my local electrical supplier and noticed a subaru impresser turbo, with the engine running, thinking the lad had forget to switch off i mentioned it to him, oh it does that, i've switched it off, but the engine management runs the engine to cool the turbo.

1 http://www.x-trail-uk.co.uk/index.php

and the aussie one

http://www.australianxtrail.com.au/ which is much more active.

2 e bay, no questions asked! But I think I also saw a link on one of the above forums. There's certainly one to the T30.

 

[colin(bridgend)]

I would have thought that by running the engine whilst stationary greater heat would have been given off as the draught from driving would have cooled the system down.

 

[WatsonJohnG]

When you stop the cooler oil is pumped to the hot turbo bearings hotspot

 

[seth1]

As RAY has pointed out,basically if the engine is turned off immedietly the oil pump becomes stationary thus no oil being pumped around the engine.usually no problems except where the engine is dressed with a turbocharger.After normal usage it takes about 60 seconds for both intake and exhaust impellors to slow down,but even on tickover the impellors still rotate.quite obviously shutting an engine down straight away leaving the impellors rotating at 25,000rpm is going to starve the impellor cross shaft of oil.Although it probably is a turbos biggest failing its not the only cause to turbo failure.

 

[cava55]

sorry i should have said for the turbo to actually slow down,you shouldnt turn the engine off immediately after a long run or strenuous activity like pulling a caravan,you supposed to let it slow right down

I have an 2007 X Trail it has had 2 new turbos fitted under warrantee and the dealer has not said that i need to let the turbo rest, he said that the turbos fitted were of poor quality !.

 

[otherclive]

I have an 04 Sorento and the handbook recommends a period of idle running after high speed or towing.

 

[RayS]

This idea of allowing the engine to idle and cool down is all very well, but how are you supposed to draw in from a motorway to refuel - sit at the pump with the engine idling for several minutes before opening the filler ? Similarly getting onto ferry, or being stopped by the law ?

 

[Morganic]

Well its a matter of choice whether you let the turbo cool down or not but don't complain if it fails on you prematurely. The theory is sound and shutting the engine down whilst the turbo is red hot will reduce its life.

Anyway a couple of minutes idling after a long run towing is good for engine and driver. I always let my car idle for a couple of minutes after a long run-whats a couple of minutes compared with the expense of a new turbo.

 

[WatsonJohnG]

This idea of allowing the engine to idle and cool down is all very well, but how are you supposed to draw in from a motorway to refuel - sit at the pump with the engine idling for several minutes before opening the filler ? Similarly getting onto ferry, or being stopped by the law ?

All the ferries I've been on haven't been boarded after a motorway stop.Its always been after a long sit in the waiting area so no turbo problem

 

[Gafferbill]

Ray S....It is all a question of degrees. Excuse the pun!!!

You only have to idle a turbocharged engine if it has been working very hard just before you stop it.

It will already have cooled considerably when decelerating in a motorway slip road and manoeuvring to a fuel pump. You can still idle for 30 seconds before switch off.

A turbocharger is a remarkable piece of engineering, looking at them in detail you would not think they would last five minutes.

An impeller is rotated at very high speed in very hot exhaust gases.

The hottest part of a running engine.

This impeller rotates in a bearing that is lubricated by engine oil.

The remarkable bit is the oil and pressure seal.

This has to allow the bearing to be lubricated and cooled by the oil, and at the same time, prevent the passage of hot exhaust gas under pressure from entering the bearing and oil ways.

It also has to prevent the oil from entering the impeller chamber and exhaust system

This seal relies on lubrication for survival under these very hot conditions.

Now the coolest part of a running engine is the intake air impeller that forces air into the engine.

The intake and exhaust impeller chambers sit next to each other and share the same oil supply.

So if you idle a very hot engine for at least a minute the very hot side of the turbocharger will cool very rapidly to a level that will preserve the seals when the engine is stopped.

 

[JTQ]

The major cause of damage with abruptly shutting down turbo diesel engines is heat sink from the turbo's hot end to its shaft with consequent carbonising of just a mear trace of the oil on the shaft, not oil starvation.

Do this a few times and the delicate balance required when rotating later on under load at possibly well over a 100,000 rpm progressively wreaks the turbo. There is no way to undo such damage and this is why some particular owners have a habit of needing new turbos.

Using the very best synthetic oil is helpful rather than keeping to the makers minimum recommendation. But by far the most important thing is to ease off the load a couple of minutes before pulling off the road and definitely to idle the turbo for about 15 seconds or whatever longer time the maker suggests, before turning the stop key.

And towing makes the situation very very much worse as the turbo is pushed and sustained at much higher levels of load than running solo.

 

[Bryan_374360331]

OK - so you should idle a turbocharged engine before switch-off. But what happens when you've driven your petrol-engined car (plus caravan) up an alpine pass and start to descend the other side? The throttle closes (it's petrol remember, and on the overrun the throttle closes completely) so there's no cooling gas for the turbo. Coasting in neutral with the engine ticking over is probably not a safe option!

Does the turbo cook?

Bry

 

[Gafferbill]

Bryan.. your turbo petrol engine is still turning on the descent and the revolutions will rise if you use it for engine braking.

This will maintain the oil supply to the turbocharger, which is turning much slower and is rapidly cooling down.

There will also be much cooler exhaust gases passing through the turbocharger as no petrol is being burnt.

It is a false assumption to think there are no exhaust gases, however the volume is less and they are much cooler.

 

[JTQ]

Unfortunately the turbo with a conventional petrol engine is a far less satisfactory marriage than the turbo with diesel.

At all times the air petrol mixture has to be stoichiometric [whew!] A limited fixed percentage petrol to air.

Thus at idle the air flow is a small fraction of what it is at power, but the burn temperature is still high; thus little turbo cooling relative to what is seen with diesels.

So the turbo in a petrol engine is doomed to a shorter life as it cant be cooled as well before being switched off.

However the best of a bad job is to idle because it still will be quite a bit cooler than if you dont.

This is the case for conventional petrol engines; direct into combustion chamber engines are different and I suspect are kinder to their turbos. My background in this area is only with diesels so others might be more helpful re petrol.

 

[Bryan_374360331]

Bryan.. your turbo petrol engine is still turning on the descent and the revolutions will rise if you use it for engine braking.

This will maintain the oil supply to the turbocharger, which is turning much slower and is rapidly cooling down.

There will also be much cooler exhaust gases passing through the turbocharger as no petrol is being burnt.

It is a false assumption to think there are no exhaust gases, however the volume is less and they are much cooler.

Ah - so it's the oil that has to be kept flowing, rather than a cooler gas stream through the turbo. That explains my alpine worry nicely - thanks.

Bry

 

[Guest]

I think most of what I want to say has already been said by various posters but I thought I would add my thoughts anyway

The concept of allowing the engine to idle before shutting down is well-established practice with all turbo engines. It ensure that the turbo bearings have a supply of cool and lubricating oil while it spools down and cools. However, modern turbos are less affected by this but none the less, it is really only important if the engine has been under heavy load by running at high RPM (going fast) or heavy load (towing). When driving at normal town speeds the turbo doesn't get so hot and isn't spooling so fast.

BTW the 2 mins at idle is a long time IMO but if you have been driving at motorway speeds, or towing, then I would still let the engine idle for a while before turning off to allow the turbo to slow with an oil supply, but it should only need 30 secs or so. That 30 sec wait is well worth it and will help any turbo engine. If you have anything of a slow-speed drive from the motorway to the service station then that is probably enough to allow the turbo to slow.