1.5DCI - Squeal for 10 seconds when engine turned off.

Forum for Engine, Exhaust, Drivetrain, ECU
Deleted User 759

Post by Deleted User 759 »

but that's not a reference to the electric water pump..... and I have just realised I asked the wrong person! I do apologise! This is why I am in bed most nights at 9! It was Quacker who referenced it.

Don't forget that the manual may not be 100% factually correct as the handbook is based on multiple engines so will only be giving generic advice, Whilst yes they will all have oil flow which will aid cooling in addition to lubrication of the bearings, they may also have a separate water feed not mentioned in the handbook. Somebody needs to eyeball the turbo core, or check the mechanics manual to see if it has water feeds going into it really.

But I stand by my idle comment, its poor practice and you should take the last 1-2 minutes being gentle!

gvmdaddy
Posts: 2245
Joined: Thu Jun 19, 2014 11:28 pm

Post by gvmdaddy »

I agree with the above, but a little difficult to do if you're only doing a stop off on a motorway!
Deleted User 1571

Post by Deleted User 1571 »

Almost all car turbochargers for the last decade are water cooled. They are also oil cooled of course and it is the oil that will bake into a gloop and ruin the turbo if abused by the driver. Oil pressure is also critical to lubrication and stopping a hard worked engine under load, such as stalling, can also ruin a turbocharger.

I would be very surprised indeed if the K9K with variable nozzle turbo did not have a water cooling circuit, and indeed an electric water pump to circulate the water through the turbo after the engine has been stopped when the ECU deems it necessary.

A proportion of the exhaust gas, that which is recirculated back into the inlet manifold, is also water cooled.

Someone asked where the water came from. Think about that for a moment. Where would he think that cooling water would come from and the resulting stored heat radiated to atmosphere?
Last edited by Deleted User 1571 on Fri May 06, 2016 10:02 pm, edited 2 times in total.
Deleted User 1571

Post by Deleted User 1571 »

gvmdaddy wrote:I agree with the above, but a little difficult to do if you're only doing a stop off on a motorway!
Why? You come off into services at light load, find a place to park, park and take your safety belt off, by which time you have effectively idled the engine for a minute or two which is sufficient cooling and time for the turbo to spool down.

If towing or driving like a loon, extra time should be allowed for cooling before shutdown.

Stalling is very tough on hot engine components including the turbo. The button-start models actually automatically restart immediately but others should manually do so ASAP to avoid potential damage.

For these and more reasons I am very pleased that the auto-stop-start economy system doesn't often work on the Qashqai. I always make sure that the engine has cooled on all vehicles thus equipped, but I'm a bit fussy about my engines. I may drive them hard when warm but I do look after them.
gvmdaddy
Posts: 2245
Joined: Thu Jun 19, 2014 11:28 pm

Post by gvmdaddy »

Lots of 'if's and maybe's' above and not much fact. Yes, some offer 'best practise' such as driving slower under light load ffor a few minutes prior to stopping, but in the real world this is not aways possible or practical, so in these circumstances stationary idling must be better and the cocorrect option rather than cutting the ignition straight away.
brianthelian
Posts: 97
Joined: Tue Jul 14, 2015 3:03 pm

Post by brianthelian »

hi thteesixty i have been looking in the manual for j11 and page EM.34 on troubleshooting it asks if the customer ALLWAYS runs the vehicle in idle speed to cool engine oil down after driving. (under turbo trouble diagnosis) i saw the exploded view, the drawings are atrocious thumb nail and when made larger are illustrated as bad, but it does show a water feed. and also oil (for lubrication?) as the turbos run very hot i suppose the water needs to circulate or it could boil eh_? or perhaps its to cool the oil as well but if it is, why ask the customer if they run on to cool the engine oil when the engine has an oil cooler and a pump? the more i read the less sense it makes. if a picture paints a thousand words WHY explains a thousand pictures no?
brian
Deleted User 1571

Post by Deleted User 1571 »

It makes perfect sense to me, but I've grown up with diesel engines. The last petrol car I had was a Jaguar XK8 back in 1997/8.

On shut down the water, even if it is forced to circulate after shut down, will inevitably boil in many of the hottest areas even though the system is pressurised to raise the boiling point. Areas such as around the exhaust valves and in the turbo. Steam is a very efficient heat absorber. It takes the heat away quickly.

Oil pump stops as soon as engine shuts down, but you can correctly assume from what you have read that shut-down procedure is far more important than the owner's manual would have you believe. Yet it is far less of an issue with today's water-cooled turbos than it used to be. A well driven turbocharger should last the full life of a modern engine, so a quarter million miles is achievable. 150k very commonplace with no more than routine maintenance.
brianthelian
Posts: 97
Joined: Tue Jul 14, 2015 3:03 pm

Post by brianthelian »

thanks quaker, good info!
brian
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