Bobby, I presume you are using the Teflon
coat silicon coolant “O” rings and not the stock Mazda ones. What
I have had happen to me after sitting for a long period (particularly in cool
weather) is that apparently these harder “O” rings tend to set up
or not seal as well as the softer stock “O” rings. As a
consequence, I have come out to find a drop of two of green coolant hanging off
my exhaust pipes. To make a long story short after pulling the engine through
a few times and then firing it up and running it up to 160F for about 2
minutes, the problem disappeared.
I have also found that if you do indeed
have a small leak (the quantity you mentioned suggest that) that firing up the
engine perhaps permits some combustion gases to enter the coolant galley –
this raises the pressure in the coolant galley which turns around and pushes on
the seal seating if for a secure seal.
Two things to watch for – if you do
have a serious leak into your coolant system, your coolant pressure gauge
should reflect this. After I had severely and totally cooked one of my O rings
due to a hasty rebuild that resulting in the triangular part of the apex seal
ending up between rotor and side housing – which created so much friction
it turn the iron housing blue for the area the size of a sliver dollar and shrunk
the O ring in that area down to little more than a tread in diameter, I still
flew from North Carolina to Mississippi. I did notice that my coolant pressure
increase approx 1 psi for each 45 minutes of flight. By the time I arrived at Mississippi, the coolant
pressure was up to 18 psi (temperature was still OK).
The system was still sealed. Around 1
hour after I landed I was at the aircraft cowl – off and while folks
watch I popped the safety release valve on the radiator cap and a stream of
greenish liquid shot about 3 feet into the air. So the combustion gases
actually kept the seal sealing (more or less) sufficient to make a long flight.
Good Luck, Bobby
Ed
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Bobby J. Hughes
Sent: Friday, May 21, 2010 4:45 PM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Rear Rotor
Coolant Leak
I have developed a small coolant leak in the #2 rotor of my renesis. It
seems to be limited to the engine sitting for long periods of time. I
discovered it when checking the plugs after the engine had not been started for
a couple of months while fitting the new supercharger. The leading plug was
wet. Pulling the prop through sprayed some coolant out of the leading plug
hole. I checked the fluid level and it was a little lower than I remember. I
added some water and marked the level on a stick for reference. The next day I
check the level and found no measurable drop. Since I had just installed the
larger supercharger I decided to do a few ground runs and check the coolant for
leaks and keep a close eye on the water pressure. I made several ground runs
and everything was normal. The plane was schedule for body work at a paint shop
as soon as I could make the 50 mile trip. I waited a few days and rechecked the
fluid level. Again no measurable drop. I then made three short flights around
the airport to check out the new supercharger and kept a close eye on water
pressure and temps. Everything was normal. After checking the coolant level the
next day I made the trip to the painters. The flight was normal but the pilot
was a little nervous.
The plane has not been started for six weeks and it sprayed maybe two
tablespoons of coolant when pulling the prop through. I did not have my
measuring stick but I could tell coolant level was a little lower then the last
time I had checked it.
I will most likely have to replace the o-ring. I overheated one time
last summer during a ¾ mile uphill taxi and OAT above 100F. The tarmac temps
could have been 115F. I shut the engine down when the coolant temps got to 225F
but they kept climbing. I think it took two gallons of water to refill the
system.
Since my water pressure is normal and does not leak down rapidly after
shutdown is it possible the engine heat is sealing the O-ring ? Maybe I just
need to re-torque the big bolts.
Bobby Hughes
RV10 Renesis