diesel turbo cool-down period?

[m0lt3n]

i have been wondering...there is a lot of different opinions on how long your car must cool down(at idle) after being driven hard?
i am wondering who wil actually sit for a full minute in their car and let it idle in for example a parking lot?

does anyone have an idea how fast a turbo cools down...meaning should cooldown even be a thought when you will drive again in half an hours time?

i just go slow for the last few km to home,low revs, then the car will also be idling while i open my garage and so on.

some inputs would be appreciated,thanks!

 

[dvst8]

I do the same with both my cars, last few kms drive off boost and then give it about 30 seconds of idling before switching off.

 

[P1000]

Dude, turbos glow red sometimes and can take ten minutes of idling to cool down. So it is not a case of it will still be the same temp when you come out of the shop. The idea is to let it cool down enough so that the oil will not coke onto the shaft when it stops being circulated. Best is to drive like a granny the last 3minutes of your trip.

 

[Luis Malhou]

I do the same, just drive easily after a long drive, by the time I get home its should be ok. I am speaking on my Ranger 2.5TD and 335i. My ranger has 180000km on the clock and i sent it in for a full service, including injectors, pump service, clean diesel tank and check pressures etc. Turbo boost pressure was tested and is boosting less than a new one by 5%.. not bad for its age. The guys at the Bosch centre advised that it certainly does help to lengthen the life of the turbo.

 

[mo_s]

lol take the last few mins easy...wen u stop put on a nice fav song of urs...n after that shld be safe t switch off :rollsmile:

btw, u should also let the motor and turbo warm up before driving...wen cold

 

[petrivanzyl]

I heard it is actually bad to be idleling to let it cool down.

With stop/start the engine switches off so no cool down?

 

[Sabretooth tiger]

Dude, turbos glow red sometimes and can take ten minutes of idling to cool down. So it is not a case of it will still be the same temp when you come out of the shop. The idea is to let it cool down enough so that the oil will not coke onto the shaft when it stops being circulated. Best is to drive like a granny the last 3minutes of your trip.

+1

 

[JENICH]

I heard it is actually bad to be idleling to let it cool down.

With stop/start the engine switches off so no cool down?

The new technology of the engine switching off when standing still does not help the theory of letting the turbo cool off by idling.

Maybe cruise home after boosting

 

[SP33DYV]

I used to drive very slowly for the last 5km to home with the Hilux 3.0D4D and then let it idle for 30 secs before switching it of. The real problem arises when you driving on the highway and pull into a gas station to fill up and switch it off immediately. I used to make a point of letting it idle for a minute or two in this situation. I sold the Hilux in March so I don't have this issue anymore.:fencelook:

 

[herr bmw]

well on the navara,it doesnt get pushed hard but we still let it cool down for 1 to 2 minutes,and the navara is got 160 000km+ on the turbo.

did the same on the golf,but +/-44 000km on the turbo and the turbo was starting to squeal again.

the funny thing is i have got into habit with the navara and let the bm cool down for the same amount of time:rollsmile:

 

[dvst8]

I heard it is actually bad to be idleling to let it cool down.

With stop/start the engine switches off so no cool down?

Good point.

 

[m0lt3n]

stop start does show that bmw doesnt think much of turbo cooldown...

i do try to let turbo cool of where i can...but i dont think people realize how long a minute is...
and then of course, sometimes there is a reason for driving hard,being in a hurry. so now you hurry to wherever and then wait for the turbo to cooldown.

from there my question will the turbo cool down significantly in say ten minutes before you drive of again.


i once read something about a blow of valve removing the need for this kind of cooldown. that true?

 

[Ralf*]

the problem is not so much the actual turbo case but the bearing between the inlet and exhaust of the turbo, if this is left to soak in the high heat enviroment, the oil becomes burnt and brittle around the bearing, causing bearing failure.

allowing a turbo casing to cool down and normal engine oil to circulate the hot bearing will allow the bearing to remain lubricated with fresh oil, and prevents the oil from becoming stagnant and thus burning/becoming brittle thus extending the life of the turbo.

I normally drive carefully for the last 2-3 mins and when I park, I unplug the Garmin Nuvi, it then starts a 30 second countdown due to loss of external power, thats how long I allow the car to idle before I turn it off.

 

[CamZo]

If you have motorplan who cares bmw dont give any recommendations or advice neither do other manufacturers lol but we love our cars... Best is to let it idle for 1 minute open your window then gather your stuff jump out of car.... Check if it is safe ( we do live in SA) put hand through window turn ignition off and close windows holding the lock ke. Lol thats more then a minute!

 

[Philip Foglar]

Okay a few things, mostly to add to what has already been said, but...

With my Isuzu bakkie I am gentle with it when cold, and after driving as I get close to my destination I do a granny style cool down by using gentle and low throttle inputs and allowing the engine to run under off throttle as much as possible since then it is just passing cool air through the turbo and engine. Once stopped I let the engine idle for at least a minute based on the overall ambient temperature and how effective the cool down drive was. Now, another issue to consider, the Isuzu has a normal viscous fan so when idling there is always some form or air flow over the engine and through the engine bay. With a modern diesels that make use of an electric fan that only runs when needed, you may find that idling can lead to a form of engine bay heat soak, so in this case I would say best is to adapt a style of driving that allows for a cool down period. The other thing to consider, it's also the turbo spinning at high RPM from being run boost, so driving gentle allows the turbo to return to a more calm speed/temperature, at least this has always been my way of seeing it.

On particularly hot days my garage gets very hot inside, so when coming home I will let the engine idle and often open the bonnet to help, maybe going a bit overboard, but I have sympathy for the turbo, and even with my non-turbo cars I often do the same thing - also good for the bonnet's paintwork... :thumbs:

 

[netercol]

having lately fiited a EGT guage + sensor to my 330d, i have noticed the following.

absolutely hammering the car for 30 seconds plus will see EXHAUST temps of about 700 celcius (or holding WOT for more than say 15 seconds) going back to normal driving sees temps fall quite quickly, with temp for normal driving rarely going over 200c .. open road driving can go as low as 100c..

taking into consideration that the temp in the turbo center housing does not (or should not) go much higher than about 120c, it would seem that coking will not be an issue with normal driving and modern oils..

if on the other hand you have really hammered the car, and i mean really , and then immediatly switch of the engine, there might be enough heat soaking back into the center of the turbo to coke the remaing oil.. but unless you do this on a fairly regular basis, or use a really inferior oil, i dont think coking is much of an issue on turbo diesels..

petrol turbo's on the other hand run much higher exhaust temps..

 

[mikecw]

My mate's Nissan HardBody 3litre turbo diesel has over 290 000km's.
Still on the original turbo, motor, injectors etc.
He always lets the motor warm up for a minute before driving off slowly and another 2 minutes idle before switching off at destination.

And is a strong believer of changing oil and filter every 7500km.

 

[Twinz]

I dont have a cool down period for my diesels. Only a warm up in the morning until the revs settle. No revving when the motor is cold. With the 335, I keep the car outside after a hot run to cool down before pulling it into the garage. I also use the Max Cool feature which is part of the tune on the car which cools the motor down rapidly. But thats about it...all in my stride.
:thumbs:

 

[P1000]

And is a strong believer of changing oil and filter every 7500km.

That is a waste if you use good oil.

BTW, my 530d is also on 290kkm with original injectors, turbo, engine etc, looking at the service history, some oil services were only done at 25kkm intervals (not that I would ever do that). The think is modern "synthetic"* oils last as long as the service interval, and you gain nothing by changing it more often, unless you use 500ppm diesel instead of 50ppm, or have a petrol and never travel on the highway for 20km+.



*they are mostly group III, except Mobil 1 and some Amsoil products, which are proper group IV Synthetics made from PAO

 

[m0lt3n]

i read an oil study on bimmerforums once where the conclusion was basically that your oil only starts functioning optimally at 7500km. but this was for petrol cars without turbo i think.

why would a diesel turbo run cooler than a petrol turbo?