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Online Gérrard

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Boiling a Water Cooled Engine
« on: November 14, 2017, 01:23:11 pm »
Sometimes while riding in technical terrain the bikes engine will be hot, with the fan blowing. You find the need to stop and the fan is still on.

Does it matter to the engine that you switch the bike off, or should you let it idle until it has cooled and the fan switches off.
A F'ugly is a different sort of bike, the 1150 is boring and the 1100s makes me smile.

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Offline dirtyXT

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Re: Boiling a Water Cooled Engine
« Reply #1 on: November 14, 2017, 01:25:29 pm »
doesnt matter to the engine but im sure it matters to the radiator. i would think the fan cools the water in the radiator for a bit. no harm no foul.
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Re: Boiling a Water Cooled Engine
« Reply #2 on: November 14, 2017, 01:32:19 pm »
I'm thinking that while the fan is on it means you still have boiling water circulating through the engine being cooled. You switch the bike off, that boiling water just sits there going nowhere, under very high steam pressure.

And a super heated engine not cooling down fast enough as the fan would do and the way its designed. Lots of pressure on hoses, pump seals etc.

The bike was designed for operating temperature, so let it cool off first.
A F'ugly is a different sort of bike, the 1150 is boring and the 1100s makes me smile.

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Offline subie

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Re: Boiling a Water Cooled Engine
« Reply #3 on: November 14, 2017, 01:33:33 pm »
I would go with the idle until fan switches off. Even better if the area or terrain will allow for a cooling off
ride.
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Offline Andre E

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Re: Boiling a Water Cooled Engine
« Reply #4 on: November 14, 2017, 01:48:09 pm »
There is nothing sinister that can happen to your engine if you just switch it of, even if it ran near the top limit of operating temp.
Water in your cooling system can only boil if it was not full to capacity or sprung a leak.
A closed cooling system allows a certain build up of pressure, thereby raising the boiling point of the coolant.
When you switch off an engine, it stops making heat, immediately.
Hot spots will not form, heat is still conducted by the coolant even if it does not circulate.
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Offline Vintage_Mania

Re: Boiling a Water Cooled Engine
« Reply #5 on: November 14, 2017, 01:56:12 pm »
There is nothing sinister that can happen to your engine if you just switch it of, even if it ran near the top limit of operating temp.
Water in your cooling system can only boil if it was not full to capacity or sprung a leak.
A closed cooling system allows a certain build up of pressure, thereby raising the boiling point of the coolant.
When you switch off an engine, it stops making heat, immediately.
Hot spots will not form, heat is still conducted by the coolant even if it does not circulate.

^^^^This.

Sodra jy die motor afskakel, skakel jy ook die bron van die hitte af. Dit kan nie warmer word nie, net kouer. En soos tereg genoem, is die kookpunt van 'n geslote verkoelingsisteem hoër as teen normale lugdruk. Sodra die water/vloeistof begin kook, kan dit nie meer die hitte absorbeer van jou motor nie, en daarom is daar 'n kans dan dat dit dan kan skade lei, dit gebeur gewoonlik as dit nie vol genoeg is nie of as daar 'n lekasie in die stelsel is en dit nie druk kan opbou nie.
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Re: Boiling a Water Cooled Engine
« Reply #6 on: November 14, 2017, 02:00:32 pm »
Thanks. Dit maak sin.
A F'ugly is a different sort of bike, the 1150 is boring and the 1100s makes me smile.

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Offline TheBear

Re: Boiling a Water Cooled Engine
« Reply #7 on: November 14, 2017, 02:46:30 pm »
I'm thinking that while the fan is on it means you still have boiling water circulating through the engine being cooled. You switch the bike off, that boiling water just sits there going nowhere, under very high steam pressure.

And a super heated engine not cooling down fast enough as the fan would do and the way its designed. Lots of pressure on hoses, pump seals etc.

The bike was designed for operating temperature, so let it cool off first.

I have often wondered about that.  If the engine is not running, neither is the water pump, so very little, if any circulation.
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Offline m0lt3n

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Re: Boiling a Water Cooled Engine
« Reply #8 on: November 14, 2017, 02:58:01 pm »
So assuming Gerrard got his answer...
what about turbos? different setup and they should rather still run a few seconds to circulate oil? My understanding has always been that the oil can burn on these hot spots?
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Re: Boiling a Water Cooled Engine
« Reply #9 on: November 14, 2017, 03:00:14 pm »
So assuming Gerrard got his answer...
what about turbos? different setup and they should rather still run a few seconds to circulate oil? My understanding has always been that the oil can burn on these hot spots?
Most turbo engines do not switch off but idle till the turbo reaches cool tempreatures afaik?
 

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Re: Boiling a Water Cooled Engine
« Reply #10 on: November 14, 2017, 03:02:27 pm »
The moment you switch off the engine with the temp near max. operating degrees, the coolant flow stops and a hotspot could form in the cylinder-head area.

This is not serious because, as someone has pointed out, the source of heat is gone, and coolant starts dropping in temp virtually straight-away.
 

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Re: Boiling a Water Cooled Engine
« Reply #11 on: November 14, 2017, 03:05:39 pm »
So assuming Gerrard got his answer...
what about turbos? different setup and they should rather still run a few seconds to circulate oil? My understanding has always been that the oil can burn on these hot spots?


The turbo gets it's lubrication from engine oil pump pressure, and if you switch off the engine the oil pressure drops very soon, and a high-spinning turbo could run on marginal lubrication.
 

Offline m0lt3n

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Re: Boiling a Water Cooled Engine
« Reply #12 on: November 14, 2017, 03:40:12 pm »
So assuming Gerrard got his answer...
what about turbos? different setup and they should rather still run a few seconds to circulate oil? My understanding has always been that the oil can burn on these hot spots?
Most turbo engines do not switch off but idle till the turbo reaches cool tempreatures afaik?

Very very few that actually does that, most I think is DIY mods actually.

But this makes me wonder what is the rationale behind the stop/start tech. My car could have worked pretty hard and it will still stop. So guessing it comes down to 2SD's explanation (although could =/= should). Or the car is capable of much higher temps before it will intervene.
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Offline TheBear

Re: Boiling a Water Cooled Engine
« Reply #13 on: November 14, 2017, 03:45:03 pm »
So assuming Gerrard got his answer...
what about turbos? different setup and they should rather still run a few seconds to circulate oil? My understanding has always been that the oil can burn on these hot spots?
Most turbo engines do not switch off but idle till the turbo reaches cool tempreatures afaik?

Not any that I am aware off these days.
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Re: Boiling a Water Cooled Engine
« Reply #14 on: November 14, 2017, 08:03:00 pm »
Anything, any time, no matter how hot, will always cool down when you remove the source of heat - do not think a motorbike engine works differently or is special in any way.

Cars do the same and we just get out and walk away, without even thinking about it.
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Re: Boiling a Water Cooled Engine
« Reply #15 on: November 14, 2017, 08:36:08 pm »
Your cooling fan is a good indicator whether your cooling system works well or not.

Your cooling system, pressurized slightly when hot, will boil at around 105degrees C.

Your thermo switch, or fan switch will start the fan at around, say 95degreesC., and switch the fan off again at around 85degreesC.

The above is rough estimates, and I used it to indicate that the fan will start long before the engine overheats, and by hearing the fan come on AND off, you know that your
cooling system is working between those guidelines.

 

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Re: Boiling a Water Cooled Engine
« Reply #16 on: November 15, 2017, 03:19:36 am »
Also remember that WATER in the cooling system can boil at around 105 degrees.

COOLANT in the cooling system raises that temp significantly. Never ride without antifreeze / coolant.

It also lubricates the system (pump) better than water, and it also helps prevent corrosion too.  :thumleft:
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Re: Boiling a Water Cooled Engine
« Reply #17 on: November 15, 2017, 08:48:54 am »
KTM 690 would actually just heat up more if idling.  In the early years when we were still trying the 15 min idle reset, mine would puke coolant before the 15 min runs out.  From about 8 minutes, the fan would run full blast and will not stop running until you switch off.
 

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Re: Boiling a Water Cooled Engine
« Reply #18 on: November 15, 2017, 09:03:28 am »
Thanks guys. Some informative responses that I think has answered some questions for all of us.

Now... does it matter what airfilter I use :imaposer:
A F'ugly is a different sort of bike, the 1150 is boring and the 1100s makes me smile.

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Re: Boiling a Water Cooled Engine
« Reply #19 on: November 15, 2017, 09:58:03 am »
Thanks guys. Some informative responses that I think has answered some questions for all of us.

Now... does it matter what airfilter I use :imaposer:
Use a K&N.  As your compression drops due to all the dust and sand the engine digests, it will run cooler.   :pot:
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