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xQx xQx is offline
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Default steam escape incident after stopping - small problem, big problem or just stupidity? - 04-13-2017, 12:46 AM

So, I live on a long straight residential street with speedhumps, which on the way home from work generally means multiple second-gear pulls right before getting home and turning the car off.

Last night I did the usual thing, and had the JB4 on so I know what the temps were when stopping: Oil 110C, Coolant: 100C, IAT: 15C above ambient (Absolute about 45C)

All was good and normal until about 2 minutes after turning the car off, when the car started bellowing steam out of the left hand side - which (on inspection with the hood open) appeared to be coming either from the coolant overflow line back to the reservoir or somewhere at the top of the radiator. The car didn't sound like it was boiling (I've boiled older cars before, you can hear the radiator hose bubbling like a kettle) - it seemed more like the coolant system in an N54 is kept under considerable pressure, and it sprung a leak. 100C is boiling point for pure water, but well below boiling point for engine coolant solution - of course, turning the car off stopped the water from circulating, so it's entirely possible some sections were well above boiling.

I've waited for the car to cool, and it took 2.5 litres of water to bring it back to full. Idling the car seems to be normal now, water temps rise as normal proportionally to the oil temp, and there's no sign of leaks, splits or loose clamps.

I've removed the factory air diverter from the front grille to the DCI (or factory airbox), because the leak was below that. I was planning on taking the car for another drive to get it up to temperature and hopefully replicate the issue and (while trying not to burn myself) see exactly where it's blowing steam from.

But I thought I'd ask here first - any common problems with the N54 I should know about?

Or was I just an idiot and should I be idling the car down to a reasonable temperature before turning it off (like the old days with a turbo timer)?
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Weehe Weehe is offline
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Default 04-13-2017, 06:27 AM

Probably cracked the expansion tank and it steamed/leaked out.
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Default 04-13-2017, 08:40 AM

Don't rip on your car multiple times back to back before you shut it off. Your neighbors will probably like you better too.
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treehouse treehouse is offline
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Default 04-13-2017, 09:23 AM

Quote:
Originally Posted by Vorsprung_CJB
Don't rip on your car multiple times back to back before you shut it off. Your neighbors will probably like you better too.
+1

That is terrible on the car. At least let it idle for 5-10 min before shutting off.
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Default 04-13-2017, 12:19 PM

Quote:
Originally Posted by Vorsprung_CJB
Don't rip on your car multiple times back to back before you shut it off. Your neighbors will probably like you better too.
Quote:
Originally Posted by treehouse
+1

That is terrible on the car. At least let it idle for 5-10 min before shutting off.
Can you explain exactly what you say that, please ...


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Default 04-13-2017, 02:37 PM

You want to give the turbos time to cool down after a hard pull, I.E letting the car idle, or low throttle driving.


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xQx xQx is offline
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Default 04-18-2017, 07:55 PM

Hey Everyone,

Thanks very much for your advice above. I'll give the car time to cool down while running/driving in future. It'll be nice if this was just a warning...

I had heard you no longer needed to worry about the health of the turbos after hard driving because they'd redesigned the cooling system in the late 90's (thus negating the need for turbo timers) - but this sort of thing highlights:
a) Just because you can drive modern cars without warming them up or cooling them down (don't worry, I warm up the car) - doesn't mean you should.
b) My 'enthusiastic driving' is probably what normal people (and OEM warranty departments) would call "abuse".

Anyway, I was reading through @chadillac2000's build thread and he mentioned a particular hose failed in his previous car. I went for a short gentle drive over Easter to (carefully) get the car up to 'pressure', and found this hose had split:



Upon removal I found it was severely degraded - so hopefully the failure was due to the physical pressure of the OEM cold-air intake which is no longer supported by the OEM airbox due to my DCI, rather than by excess coolant pressure.

Time will tell.
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audiophool audiophool is offline
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Default 04-18-2017, 08:40 PM

That same length of plastic hose shattered when I removed it during a recent repair. Seems to be an issue from manufacturing, or incorrect specification of the material itself.


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Default 04-19-2017, 06:54 AM

I had mine do the exact same thing a couple weeks ago, look on the bottom side of that smaller line where it is attached with the clips to the radiatior. That's were mine broke, I just cut the whole little tube out and replaced it with a 3/8" section of heaterhose, not sure why they made that line so small right there. It's just asking for trouble


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Default 04-19-2017, 08:47 AM

N54's has an electric water pump that will dissipate the residual heat from the turbochargers and thus prevent from overheating even after the engine has been switched off
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Default 04-19-2017, 09:17 AM

The pump still only runs a limited time, and it doesn't circulate oil. Plus sitting still, either idling or shut off, is not the same as proper airflow through the radiator and engine bay. When it sits like that you can get hot spots in the engine, turbo and cooling system. If you have a garage you could open the hood and/or set up a fan in front of the car for a few minutes after you shut it off, if the temps are high. This engine runs hot as it is, plus it is a very confined space, especially in E8x.

Best of course is to just drive easy for a few blocks before you get home.
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