From: "Finn Lassen finn.lassen@verizon.net" <flyrotary@lancaironline.net>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: My RV-3B 13B cooling problem -- engine rebuild time?
Message-ID: <cec19b32-04dc-35f3-874f-31202d68e45b@verizon.net>
Date: Thu, 26 Nov 2020 10:06:35 -0500
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Over the last few years I've noticed more and more coolant (Evans) in 
the overflow tank.

This is an open non-pressurized system -- a header tank on top of the 
firewall -- 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 
somewhere so coolant was not being sucked back into the header tank and 
engine as the engine cooled down.

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

In a normal pressurized system, one should be able to look at the 
coolant pressure 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 
temporarily 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 
(than coolant o-ring) of what could cause coolant to accumulate in the 
overflow tank?

One more data point: on flight before last the water temp (sensor 
mounted near top of pump housing -- filler neck) dropped to 60F (same as 
with disconnected 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 lost coolant. Later I pulled the cowling and found 
about 1/3 more in overflow tank that what I'd seen last time the cowling 
was off.

Finn


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