Piper Flyer Association - Technical Know-how, Serious Fun read more

Topic-icon Oil coming out of exhaust: Navajo

  • rjrengel
  • rjrengel's Avatar Topic Author
  • Offline
  • Subscriber
  • Subscriber
1 year 7 months ago #976

I am new to Flyers and have a maintenance question for a 1975 PA31 Navajo.
Bad news, I know, but I have oil coming out of the exhaust on the left engine along with a grey smoke. Seems most noticeable during taxi and shutdown. There is oil splatter on the underside of the cowling and the left landing gear. It is about 300 hours shy of TBO on an already overhauled engine. I understand there is probably a cylinder/piston with 'blow-by' where the oil moves up into the combustion chamber. My Engine Monitor shows normal EGT CHT readings across all cylinders.
Possibly related is a lack of manifold pressure on the same engine. It is typically fine at sea-level, but MP slowly decreases with altitude.
I 'baby' the engine by running it cool (typically 400 CHT on the hottest cylinder #4) and 65% power. I know my she is getting old and tired. These are my questions:

1. how do I diagnose which cylinder? or is this a total top end overhaul (there are already 3 replaced cylinders). or is it time to buy a rebuild (this engine doesn't look like it can be overhauled again).
2. it is burning about 1 quart/2 hours, I keep it regularly topped off. Is this a 'dangerous' condition? I commute with the plane, I won't put-off the maintenance, but I have about 8 hours of flights planned before a convenient maintenance shutdown.
3. is the manifold pressure drop related to the cylinder/oil issue?


Please Log in to join the conversation.

1 year 7 months ago #978

Hi RJRengel,
Sorry for the delay in response. We were just swamped at AirVenture - figuratively signing up new members, not literally as we were a couple of years ago.
Let me check with our resident experts and I'll get back to you.

The following user(s) said Thank You: rjrengel

Please Log in to join the conversation.

1 year 7 months ago #979

I am actually more suspicious of the turbo. If the turbo bearing is bad, that could be your oil leak. In my experience, the exhaust stacks from the cylinders run so hot that any oil will have burned off before getting out of the exhaust. If the turbo is going bad, that would explain the manifold pressure drop.

I would ask you mechanic to inspect the turbo for bearing play.

The following user(s) said Thank You: Jen D

Please Log in to join the conversation.

Time to create page: 0.287 seconds