John,
Don't laugh, but I've heard that you can use flour to help locate the source of a leak.  You put flour on the suspect area, run it a little bit, and see where the flour has fresh oil on it.  I guess that the theory is that the flour soaks it up, and keeps it from spreading around.
 
The only down side would be that be fan in the back, blowing the flour away.
 
Just a thought.
 
Steve Brooks
 
 

    -----Original Message-----
    *From:* Rotary motors in aircraft
    [mailto:flyrotary@lancaironline.net]*On Behalf Of *John Slade
    *Sent:* Wednesday, February 09, 2005 1:20 PM
    *To:* Rotary motors in aircraft
    *Subject:* [FlyRotary] Oil leak

    Hi Guys,
    I've been chasing an oil leak for a while now. It only happens
    when the engine is running. When I get back from a 20 minute
    flight the cowl has oil streaks down the outside, everything under
    the cowl has an oil film on it, and the turbo is seriously
    smokin'. I could probably make a similar mess by spraying about
    1/2 cup of oil at the cowl and engine.
         Today I took the plane up and down the runway a couple of times
    and did a couple of runups with the cowl off. I seem to be a
    little down on power - (3950 instead of 4050 on static). When I
    got back the mount plate below the turbo had fresh oil on it and I
    could see air bubbling through this oil at the joint of the mount
    plate and the engine, just by the turbo. See attached picture with
    arrow. In fact the entire join between the engine and the plate on
    the right (turbo) side seems wet with oil and there's another pool
    at the front which I don't think migrated from the back.
         I get the feeling that this "bubbling" might become a fine jet of
    oil which points directly at the turbo when the engine's running,
    otherwise I don't see how oil could get up into the turbo housing
    and smoke like it does.  I'm trying to understand why there might
    be pressure here. The breather is definitely not blocked, and in
    fact, on this particular run, I'd even left the dipstick out.
    Could the bubbling air be a compression leak from the join between
    the rotor hosing and the backplate?  My oil level is maybe 1/4 -
    1/2 inch below the level of the mount plate and the plane was on a
    slight grade making the back lower. The bubbling stopped after a
    few minutes and did not return when we turned the prop.
         I'm resigned to pulling the lower cowl, sump and sump plate and
    redoing the RTV join (again), but I'm wondering - should there be
    pressure here? Is there some other problem causing this. Am I
    overfull with oil?  Could the turbo oil return be "landing" on the
    mount plate, then running back along the join? I'm planning a
    compression test next time I go down to the hangar.
         Any other thoughts or suggestions?
         Regards,
    John (13.9 hrs and holding)