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582 cooling circuit pressure valve

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Renaud

Joined: 24 May 2007
Posts: 9
Location: France

Posted: Wed May 30, 2007 10:29 pm Post subject: 582 cooling circuit pressure valve

Maybe one of you have some experience about this: on my 582 (spak-plugs up, radiator at the bottom and expansion tank at the top), the excess pressure valve normaly integrated in the plug has been removed by the previous owner, apparently based on the recommendation of a "very experienced" guy (?!) As a result, the cooling circuit is never pressurized!?



This worked fine for about 75 hours, but I just discovered that now when applying full power, the water temperature suddenly drops very significantly, below the 140 °F limit. I don't remember this behavior when I started to use my plane last year.



 I checked the liquid and the circuit: very clean, no corrosion, no obstruction. I am suspecting the absence of pressure valve, but I still can't understand why the temperature suddenly drops when applying full power.



Does one of you know the reason for pressurizing the cooling circuit: avoiding cavitation in the pump, increasing the boiling temperature of water, etc? Is there any risk of damaging the water pump when running unpressurized? 



I forgot to mention that I have a cabin radiator in parrallel with the cooling radiator, but it is currently isolated with valve, so I don't think there is any impact.



Thanks for your help

_________________
Renaud

KitFox IV - 1200. Rotax 582.

Guy Buchanan

Joined: 16 Jul 2006
Posts: 1204
Location: Ramona, CA

Posted: Thu May 31, 2007 7:01 am Post subject: 582 cooling circuit pressure valve

At 11:29 PM 5/30/2007, you wrote:

 	  Quote: 	
		  Does one of you know the reason for pressurizing the cooling 

circuit: avoiding cavitation in the pump, increasing the boiling 

temperature of water, etc? Is there any risk of damaging the water 

pump when running unpressurized?


	


Renaud,

         You've got it right on both counts, though I seriously doubt 

you can damage the water pump running unpressurized. The reason the 

temperature usually drops below 140F is that the thermostat opens. I 

usually see a 5-10F drop when that happens during warm-up. Be 

careful, if your temperature is dropping rapidly from high to low due 

to the thermostat opening you could experience "cold seizure", or 

otherwise damage your pistons. If you're see a noticeable drop it may 

mean your thermostat is not opening until a higher temperature and 

then you're "quenching" the engine; not good.

         I would look for the drop at 140 every time you warm up. If 

you get a consistent rise past 150 I'd say your thermostat never 

opened and should be replaced.

Guy Buchanan

San Diego, CA

K-IV 1200 / 582-C / Warp / 100% done, thanks mostly to Bob Ducar.

_________________
Guy Buchanan
Deceased K-IV 1200
A glider pilot too.

Renaud

Joined: 24 May 2007
Posts: 9
Location: France

Posted: Thu May 31, 2007 12:47 pm Post subject: Re: 582 cooling circuit pressure valve

Guy,

Thanks for your quick reply! I have no thermostat!

I tried it today after manoeuvering the cabin radiator insulating valve and everything is fine now. No way to reproduce the problem... Maybe this valve was just stightly open and some cold water from the cabin radiator was pumped only with full RPM?!



However, I still don't understand the reason for having (or not having) a pressure valve  at the expansion tank plug.



Based on all I read about "cold seizing", I will definitely install a thermostat.



Anyway, thanks again for your reply. Happy flying with Kitfox!

_________________
Renaud

KitFox IV - 1200. Rotax 582.

Guy Buchanan

Joined: 16 Jul 2006
Posts: 1204
Location: Ramona, CA

Posted: Thu May 31, 2007 8:31 pm Post subject: 582 cooling circuit pressure valve

At 01:47 PM 5/31/2007, you wrote:

 	  Quote: 	
		  Maybe this valve was just stightly open and some cold water from the 

cabin radiator was pumped only with full RPM?!


	


Glad to hear it worked out.



 	  Quote: 	
		  However, I still don't understand the reason for having (or not 

having) a pressure valve  at the expansion tank plug.


	


I guess you're talking about a pressure cap on the expansion tank. 

The boiling point of the fluid increases with pressure. With a 15 psi 

cap, (standard,) the boiling point of pure water increases 120F. I 

don't know what the glycol mixture increases, but it might be the 

same. The increased vapor pressure will also inhibit cavitation. Now 

you might think that since we never go over 180F, who needs the 

pressure? The answer is that you can get local hot spots in the water 

jacket. If these boil the local heat transfer coefficient drops 

dramatically, (vapor has a much lower heat transfer coefficient than 

fluid,) and the hot spot can turn into a hole. (This was supposedly a 

problem with the 912 and the reason they went to the Evans coolant.)



 	  Quote: 	
		  Based on all I read about "cold seizing", I will definitely install 

a thermostat.

No, No! You've got it backwards! Cold seizure generally happens with 
	


a thermostat! If you don't have a thermostat it's harder to get "cold 

seizure" but you can run the engine too cold, with the concomitant 

poor performance.

Guy Buchanan

San Diego, CA

K-IV 1200 / 582-C / Warp / 100% done, thanks mostly to Bob Ducar.

_________________
Guy Buchanan
Deceased K-IV 1200
A glider pilot too.

Renaud

Joined: 24 May 2007
Posts: 9
Location: France

Posted: Fri Jun 01, 2007 2:07 pm Post subject: Re: 582 cooling circuit pressure valve

Understood for the pressurized circuit. Thanks.



Regarding the thermostat, as I don't particularly need to improve the performance, I understand I don't need it. All I want is to avoid any kind of seizure. However, I am still a bit concerned about temperature falling below 140°F during descent or long approach. No risk of damage or seizure in these conditions?

_________________
Renaud

KitFox IV - 1200. Rotax 582.

Guy Buchanan

Joined: 16 Jul 2006
Posts: 1204
Location: Ramona, CA

Posted: Fri Jun 01, 2007 4:22 pm Post subject: 582 cooling circuit pressure valve

At 03:07 PM 6/1/2007, you wrote:

 	  Quote: 	
		  However, I am still a bit concerned about 

temperature falling below 140°F during descent 

or long approach. No risk of damage or seizure in these conditions?


	


Of course you can run the engine down to -20F and 

it will run. After all, snowmobiles start from 

this condition all the time. The problem comes 

from doing any temperature change too fast. 

Cooling is especially tricky, as the sleeves are 

shrinking faster than the pistons, which can 

ultimately cause damage. What's the max rate of 

change? I have no idea! Maybe someone else can help.

Guy Buchanan

San Diego, CA

K-IV 1200 / 582-C / Warp / 100% done, thanks mostly to Bob Ducar.

_________________
Guy Buchanan
Deceased K-IV 1200
A glider pilot too.

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Mon Jun 04, 2007 4:04 am Post subject: 582 cooling circuit pressure valve

Don't forget the higher up you go the lower the  boiling point of water, or any liquid for that matter.  That is why you  can't get a boiled egg in the highest mountains...Don't even think of making a  "good" cup of tea!! Without the pressure cap you will find the same  thing that happens without it in a car.  The engine will work pretty well  until enough of the fluid boils off then the temperature will sky rocket!   When I first got my 'Fox with the 582 the builder had plumbed it with the surge  tank Teed into the return line to the engine.  This of course vented  the the cooling system to ambient pressure.  Needless to say flights were  very short before the coolant needed replenishment and you don't do that on a  warm engine.  The cooling system was re-plumbed with the surge tank on the  low pressure side of the filler cap and now it works real  well!

 

[img]cid:306105911(at)04062007-16A7[/img]  

 Noel Loveys, RPP, AME intern

 Campbellton, Newfoundland, 

 Canada

 Kitfox Mod III-A, 582, B box, Ivo IFA

 Aerocet 1100s

 noelloveys(at)yahoo.ca (noelloveys(at)yahoo.ca)

 

 

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Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Mon Jun 04, 2007 6:35 am Post subject: Re: 582 cooling circuit pressure valve

Hi Renaud,



If you want a little higher temp and a more stable temp. Replace your coolant with some Evans NPG+. They claim you can run a no pressure cap, but Rotax recomends you still use the pressure cap. Evans is a waterless coolant that a lot of Rotax 912 owners use. Evans is used in lots of other applications like other planes, cars, motorcycles, ect... I have used it for 5 years and I'm happy with it. No water, no corrosion. It will raise the boiling point of your coolant from approx. 275F to 375F before it boils. It won't hurt anything. Try it and if you don't like it then go back to the 50/50 coolant. It's just something different. Some people like it and others have mixed opinions.

_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

rparigor(at)suffolk.lib.n
Guest

Posted: Mon Jun 04, 2007 9:52 am Post subject: 582 cooling circuit pressure valve

"Evans NPG+. They claim you can run a no pressure cap"



This may be stated by Evans, but they expect you have the pressure cap on

the suction side of pump. I am not familiar with 582 system, but a 914 has

cap on high pressure side. On 914 will be running .9bar



Ron P.

Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Mon Jun 04, 2007 1:06 pm Post subject: Re: 582 cooling circuit pressure valve

Rotax still wants a pressure cap. 13 psi or .9 bar works well.

_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

Renaud

Joined: 24 May 2007
Posts: 9
Location: France

Posted: Tue Jun 05, 2007 1:27 pm Post subject: Re: 582 cooling circuit pressure valve

Guys,

Thanks for your support. As soon as I can, I will make a test with a pressure cap from a friend. I just hope my rotary pump seal will not leak with pressure  in the cooling circuit. Maybe the reason the previous owner removed it?



I was also thinking about adding a simple flap in front of the radiator to adjust the temperature during flight and limit cooling during descent. But the more complex system, the more risk of failure, mistake, etc... so I will probbaly give up this idea.

_________________
Renaud

KitFox IV - 1200. Rotax 582.

Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Tue Jun 05, 2007 1:44 pm Post subject: Re: 582 cooling circuit pressure valve

Hi Renaud,



I don't think I would worry that much about your temp. It is not 140F all the time. It won't hurt anything.

_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

Guy Buchanan

Joined: 16 Jul 2006
Posts: 1204
Location: Ramona, CA

Posted: Wed Jun 06, 2007 6:44 am Post subject: 582 cooling circuit pressure valve

At 02:27 PM 6/5/2007, you wrote:

 	  Quote: 	
		  I was also thinking about adding a simple flap in front of the 

radiator to adjust the temperature during flight and limit cooling 

during descent. But the more complex system, the more risk of 

failure, mistake, etc... so I will probbaly give up this idea.


	


         You may have already heard this. Go look at the radiator 

louvers sold by HighwingLLC. They work and should the cable brake, fail open.

Guy Buchanan

San Diego, CA

K-IV 1200 / 582-C / Warp / 100% done, thanks mostly to Bob Ducar.

_________________
Guy Buchanan
Deceased K-IV 1200
A glider pilot too.

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