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Discussion Starter · #1 ·
Question 1. Sorry if I'm being a tad uneducated but this is my first diesel, after driving should I let it run for a short amount of time to allow the turbo to cool down?

Question 2. If yes and if not doing do can cause damage, is the stop start feature going cause that damage?

Thank you
 

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My last diesel (a Mazda) said in the user manual that you should run the engine for a short time at low revs after a period of fast driving. As my Kia is not a diesel I haven't looked to see if the instruction is the same. Question 2 is very interesting - see the "change gear indicator" vs DPF thread for another instance where too much fancy technology can be counterproductive.
 

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Discussion Starter · #3 ·
That is my thinking! If you are supposed to run for a short time at low revs, is the stop start causing long term damage?
 

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That depends on the turbo. A lot of modern turbos are water cooled which are not as fragile as the older purely oil cooled types as the water keeps on circulating even with the engine off.
 

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Well in every motor magazine I've read the U2 CRDI 1.6 really gets a talk up on how state of the art it is, so maybe. I always hear a humming coming from my engine after a drive, the shorter the drive (or more to the point how warm the engine got) varies the time I can hear it for. I was informed its most probably the ERG valve, but could be a water pump
 

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I don't think the water pump keeps running with the engine off, although it is sometimes done if a car has an electric water pump. The water pump is there to assist circulation but the hot water will circulate on its own, or thermosyphon as it is called. Many pre 1950's cars had no water pump at all.
 

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Discussion Starter · #8 ·
Surely it's a bad thing though. For example you've been on a decent run and hit a set of lights and it cuts out without waiting? Regardless of pumps etc. I've always been led to believe a turbo should be left a short while first before turning off?
 

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In the days of the early turbo's it was standard practice to allow the turbo to spool down and allow the oil to cool it down.
Shutting the engine down immediately after a high speed run would cause the oil in the bearing cavities to coke up and eventually the seals and bearings would fail.

The old Saabs were notorious for this.
Technology has since moved on with the advent of synthetic oils, improved bearings, seals & cooling.
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I still can't get away from a bit of engine TLC and for instance on a high speed motorway run, when pulling in to fuel up, I will put it in neutral at the 300 yard exit marker and coast in to the pumps.

If I had stop start I would only use it for town driving & switch it off the rest of the time.
I have been told by my dealer that at temperatures below 5ºC the system deactivates... is that true?
 

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Techno said:
The water pump is there to assist circulation but the hot water will circulate on its own, or thermosyphon as it is called. Many pre 1950's cars had no water pump at all.





cars with out water pumps had no pressure caps on the rad system and massive hoses along with massive amonts of water in the systems

no modern cars thermosyphon as you call it. When a engine stops then the water circulation stops but the pressure remains this pressure increases the boiling point of the water allowing cars to run at 110c with out boiling up and also deal with the increased hot spot cooling that happens in the block and cylinder head area



stop start is disabled until oil and coolent temps are reached

unless you rev the car up before switching it off then the turbo speed is low because most modern turbos are variable vane units and they will be a low pressure setting at idle as no boost is required
 

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I think we will have to agree to disagree on that point. I will agree that without the pump running they don't circulate particularly well but the water will circulate until it cools down enough to close the thermostat.
 

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It's an electrical water pump on the U2 1.6 CRDI is it not? It could run all day if the thermostats open.
 

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We have had them run for a minute or so with the fan after the engine is turned off. It prevents heat soak and makes the engine easier to restart. They actually draw quite a few amps so battery management is important.
 

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RichieD76 said:
It's an electrical water pump on the U2 1.6 CRDI is it not? It could run all day if the thermostats open.





No the waterpump is belt driven not electric part number is 1.6d engine 251002A200 or 1.7d 251002F000 put thease into google and it will show you the parts image.
 
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