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Today I had the oil pressure drop considerably along with the smell
of hot oil while I was in flight. Fortunately I was still within about 3 miles
of the airport after take off. Had I been farther away I'd have ended up
in the swamp. I reduced power to reduce oil pressure and returned to the airport as quickly
as possible. There was about 3/4 to 1 qt still in the engine when I
drained it. I pulled the cooler and stood it up with the intakes up and
filled it with oil. I noticed a seepage around one rear corner. I use an
adjustable rear bypass valve like the racing guys use. I adjust it so that
I get a cruise pressure of 40 to 50 at 170 to 180 degrees. On takeoff it will
typically show "99" on the EIS 2000 ... so I don't know what it really is. That's
the max reading on that instrument. I always wait for 100 deg Oil Temp
before takeoff so I'm not going with cold oil. The cooler is the Jegs part
number 130-70265 recommended by Sonex.

Any ideas on how to avoid a reocurrence? Is there a better cooler that
will withstand more pressure? I can back off the valve a little but will likely
see OP's in the 30s at cruise with hot oil.

Another option would be to do what I did on my previous Sonex and
install an oil temp bypass valve that doesn't put the cooler in the
circuit until the oil temp reaches 180. I didn't do that on this one
to save weight .. but it's an option.

RT

floridasonex wrote: I adjust it so thatI get a cruise pressure of 40 to 50 at 170 to 180 degrees. On takeoff it will
typically show "99" on the EIS 2000 ... so I don't know what it really is. That's
the max reading on that instrument. I always wait for 100 deg Oil Temp
before takeoff so I'm not going with cold oil. The cooler is the Jegs part
number 130-70265 recommended by Sonex.

Hi Roger,

That's scary stuff! Great job on keeping calm!

I don't really know what the answer to your question is but on the Corvair I wait until the oil temp is at 150ºF before going to full throttle. Don't remember what's recommended for the Aerovee for oil temp before full power application. I have a cold oil pressure of 42-45 PSI and usually see 37-42 PSI in cruise flight which is where it's regulated to run. Hot idle is at 26 PSI. I thought to suggest that you check the bore for the oil pressure control valve but I know you are smart enough to have already done that.

I'm curious as to what you find. Perhaps a call to Kerry is in your near future ...

Dale
N319WF

I would check the engine with a mechanical oil pressure gage as a first step. The electric vdo senders are notoriously inaccurate. Youight have the pressure set too high and not even know it.

Keith

Let me start with been there done that and bought the t-shirt( and I should have bought 100 acres of beans). At around 50 hours I started up on a beautiful 50 to 60 degree day. I taxied out and did a run up with all normal and took off. 5 miles from the airport the engine quit and without being able to get a restart I landed in a bean field. Landing was uneventful and the only damage was a wheel pant. Back at the airport I found a leak in the oil cooler on the right rear corner that had drained all the oil from the engine. I also found a large patch of aerosoled oil on the ground. On tear down I found the second from the rear crank journal badly burned and the rod bearing melted and oozed out of the journal. A complete overhaul was done (only $900.00 including crankshaft...try that with a Lycoming/continental/jabiru). During tear down i found the rear oil pressure relief valve stuck in the closed position. I had to use a screw driver to wiggle it loose to remove it. I then smoothed the edges of the valve follower and made sure it didn't catch in the valve path. I replaced the oil cooler with the same part number from JEGGS and haven't had a problem since. However it should be noted that I now look back at my start up point for evidence of oil on the tarmac, and I added a mechanical oil pressure gauge as a crosscheck to the VDO sender that feeds my Enigma. I also use the adjustable pressure valve , but have not adjusted it for a year. If it was me with what i know now I would first suspect the rear oil pressure relief valve and make sure it does not stick.

Thanks guys for the input. I know it's happened to others. Draining the remaining qt or so of
oil and checking the oil cooler was about all I got done. I was driving down to Miami for
the weekend so I had to get going. I have checking/cleaning the bores on the pressure relief valves on my to do list. I have a mechanical gauge and I checked that against the EIS / VDO setup early on but
I'll do that again when I run it to check for leaks.

I'm going to go ahead and plumb the cooler bypass valve in since I have one on hand. I used that on
my Titan Tornado and added one to my previous Sonex (I didn't build it). My motivation for that was
I was in Nebraska and it was hard to get the oil to warm up in the winter .. but an added benefit is
keeping oil from the cooler until it's hot and pressure has stabilized.

I'm glad I wasn't too far from the airport and got down before all the oil was gone. At least I
had some oil pressure until shut down.

RT

What viscosity oil are you running?

VR-1 20W-50 like called out in the service bulletin on oil

Here's the change I made after the oil cooler failure. I added an oil bypass thermostat that I had
gotten and didn't install. I have used it on two other experimentals .. one a Sonex/Aerovee and
the other a Jab 2200 on a Titan Tornado.
I test flew it after ground running to check for leaks. Right after start up I was seeing oil pressure
in the upper 40s and at cruise and 190 deg oil temp I was seeing around 36lbs. I'm sure the difference
from the very high I had before is the extra hose I'm pushing the oil through. Today I added a shim
under the rear control valve spring .. hopefully I can pick up a few pounds with that. I didn't put
the adjuster back in the rear control port .. so I can put that back on too.

In looking at the oil system diagrams I don't see how the oil relief valve that's meant to bypass
the cooler when the oil is cold (OP high) is doing that in the Aerovee configuration where the
cooler is hooked straight to the pump. It seems like to use this function you'd have to connect
the hoses to the ports on top where the top mounted cooler normally connects. Am I seeing
this right?

RT

Robbie posted my pics in the link below. Thanks.

edited to try to fix the links


http://sonexbuildersandpilotsfoundation.zenfolio.com/p417988071/e302F0AD9

Robbie Culver
Sonex 1517
Chicagoland
Tails and Wings complete - finishing fuselage.
N1517S reserved