Today's Message Index:
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1. 08:01 AM - Re: 582 cooling circuit pressure valve (Guy Buchanan)
2. 01:48 PM - Re: 582 cooling circuit pressure valve (Renaud)
3. 09:31 PM - Re: Re: 582 cooling circuit pressure valve (Guy Buchanan)
Message 1
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| Subject: | Re: 582 cooling circuit pressure valve |
At 11:29 PM 5/30/2007, you wrote:
>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.
Message 2
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| 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.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=115823#115823
Message 3
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| Subject: | Re: 582 cooling circuit pressure valve |
At 01:47 PM 5/31/2007, you wrote:
>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.
>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.)
>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.
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