flyrotary@lancaironline.net Mailing List Archive

Mark,

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 -----

From: Mark R Steitle

To: Rotary motors in aircraft

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