Hi Ed,
I haven’t paid real close attention to
my coolant pressures up to now. Not seeing anything “unusual”,
I typically focus on other stuff. Best I recall, my coolant pressure
starts at 0 and gradually increases. I have not noticed any quick rise immediately
following startup. But then, the coolant pressure sensor is locate at the
thermostat housing (no thermostat). So, I’m measuring coolant pressures
between the block and radiator. The highest pressure I recall seeing so
far is about 24psi after running for 20-30 minutes and temps are in the 212
degree range. I have to admit that I’ve been ignorant and
uninformed as to the need for a cup-o-air in my system and have to this date “filled
it to the brim”. I guess I need to add a cup-o-air the first chance
I get.
I don’t follow you on the potential
damage to the o-rings. The TES o-rings are supposed to be good to 500
degrees (I let you test that theory). They’re supposed to be good
for 100 degrees over the stock o-rings, so I should have a considerably higher
margin of safety here. I would be more concerned with blowing a radiator
hose, but I’m using aluminum tubing with Wiggins type couplings, so I don’t
think I’ll be blowing them apart anytime soon. I guess the weakest
link in my system is the heater hoses. While they’re top of the
line Gates hose, I plan on changing to silicone heater hose before first
flight.
Mark
(Happy to hear you got home safely)
From: Rotary motors in
aircraft [mailto:flyrotary@lancaironline.net] On
Behalf Of Ed Anderson
Sent: Monday, June 27, 2005 9:29
PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Coolant
Leak
The phenomena which started this thread was the immediate
rise in pressure during initial start up in some installations (mine for
instance) when all air has been removed from the coolant system. Once my engine
warms up the pressure runs around 8 psi and may climb as high as 10psi if temps
are higher than 200F. It is true that higher pressure delays the
temperature that water boils at - but, higher pressure may also work against
your waterpump seal and cause leaks (just a thought). I personally prefer
to run at lower coolant pressures since my radiator cap has a max of 21-24
psi. I suspect that while a higher PSI may indeed delay the onset of the
coolant boiling - if your engine is that hot - you will probably have cooked
something (like "O" rings {:>)).
----- Original Message -----
Sent: Monday, June 27,
2005 10:07 AM
Subject: [FlyRotary] Re:
Coolant Leak
Ed,
Not to stir the swirl pot, but I thought
that it was decided some time back that higher pressures were better than lower
pressures. The higher pressures are supposed provide more margin of
safety before a boil-over occurs, permitting a thinner ethylene-glycol solution
and enabling the engine to tolerate higher temps before experiencing
catastrophic boiling. So, I’m wondering where this leaves us.
Is it better to run at low (7-8 psi) pressures, or high (28-30psi)
pressures?
Mark S.
I agree, Al, inquiring minds at least like a plausible hypothesis and I think
the discussion has led to that. Perhaps I'll leave the "cup" of
air, just for peace of mind {:>)
Ed