|
Steve-
I
run an IO-550-B. The installation is FWF from an A-36 Bonanza and though I
didn't do the installation everything was reused that could be. The vent tubing
is aluminum with only short hose sections for coupling. It runs
upward from the filler tube, over the oil cooler and through the baffling before
it turns down and wanders over to the cowl flap. It appears to be above the
filler cap at the highest point. Someone could check me on this but I'd guess
that was the arrangement used by Beech, possibly to counter a problem like
yours. The engine has 2K total time, about 400 hrs since top overhaul, pressure
is 60#. I use 9 quarts (12 qt capacity) and apart from a slight mist
off the front seal it stays squeaky clean. Almost nothing comes out the
vent tube.
From your picture that doesn't seem to be an
option but would it be possible to gain height by going over the #2 intake or
upward aft of the baffle so that any oil might separate and drain back to
the filler? Does the bit of aluminum tape in the upper photo cover a
previous routing hole?
I had also been thinking that you might have
excessive pressure inside your lower cowling. I'm trying to explain the
manometer change at 120KT- perhaps the outlet size is adequate up to
that point but not enough to allow increased flow at higher speeds. Since
your vent tube terminates inside the cowling that might pressurize the
crankcase. I wouldn't expect it to cause oil to blow out the breather
though- it might come from somewhere else if that was the case.
You have checked for leakage extensively
although initially you were wondering whether there might be leakge from
the alternator etc. From that I guess you had oil all over the rear of the
engine? I notice the vent tube ends quite a bit above the bottom of the
firewall. Air currents inside the cowling can spread oil from even a small leak
all over the place and there's a long way for the vent oil to exit.
I'd suggest a temporay extension outside the
cowling to see what that might do. The whistle hole should also be closed off.
At the very least that'd eliminate lower cowling pressure as a factor and any
flow from the vent would go straight onto the belly so you'd have a chance to
see if there was leakage from anywhere else. Also, if there's any way
to have oil drain back into the filler it might help a lot.
How much time on the engine and who built
It?
My best guesses- Bill
Wade
|