From: "Jeff Whaley jwhaley@datacast.com" <flyrotary@lancaironline.net>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] My RV-3B 13B cooling problem -- engine rebuild time?
Thread-Topic: [FlyRotary] My RV-3B 13B cooling problem -- engine rebuild time?
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Date: Thu, 26 Nov 2020 19:53:51 +0000
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I don't understand "Open Non-Pressurized" system ... if you pull negative G=
's coolant can spill out somewhere??
Regardless, if you have coolant O-ring problems you will likely see coolant=
 in your exhaust ports if your remove the pipes and roll engine over by han=
d.
Jeff

Over the last few years I've noticed more and more coolant (Evans) in the o=
verflow tank.

This is an open non-pressurized system -- a header tank on top of the firew=
all -- bottom outlet goes to the pump inlet, and near top to the thermostat=
 (cap) filler neck.

I though the problem was that there was a small leak in the system somewher=
e so coolant was not being sucked back into the header tank and engine as t=
he engine cooled down.

Now I'm beginning to think that it could be blown (or weak) o-rings allowin=
g compression/exhaust gasses to escape into the cooling passages, forcing o=
ut the coolant.

In a normal pressurized system, one should be able to look at the coolant p=
ressure gauge (I don't have that -- no sensor) and see pressure increase as=
 RPM is increased if there were blowby, I guess.

But how do I do it in a non-pressurized system? Add a pressure gauge and te=
mporarily block the hose to the overflow tank and run the engine for a few =
seconds?

I'd rather not do an engine rebuild if I don't have to. Any other ideas (th=
an coolant o-ring) of what could cause coolant to accumulate in the overflo=
w tank?

One more data point: on flight before last the water temp (sensor mounted n=
ear top of pump housing -- filler neck) dropped to 60F (same as with discon=
nected sensor), went back to land, and during and after landing temp showed=
 185F. I figured it must have been a bad connector, but was worried about l=
ost coolant. Later I pulled the cowling and found about 1/3 more in overflo=
w tank that what I'd seen last time the cowling was off.

Finn