fbpx

 

Hello Rotax-Owner forum members,

On my last flight I noticed burned oil smell after engine shutdown. I removed the cowling to find quite a bit of oil in the bottom aft part of the engine. The water pump was soaked in oil, migrated forward to the lower oil drain banjo fitting and dripped on the muffler, some was found around the flywheel area and exiting the LH vent hole. The bottom of the ring mount was soaked in oil. Even some made it to the bottom of cylinders 1 and 3. 

I could not pinpoint the exact source of the oil leak although I did see some streak at the bottom of the housing that has the aft crankshaft oil seal (looking with a mirror through the flywheel holes). So my suspicion is the oil seal but don't want to jump to conclusions. I also have to admit that besides the streak of oil on the boss where the oil seal is located I can't see that much oil aft of the seal or in the flywheel area to cause such a large mess. The coils in this area are mostly dry and I would think they would be much wetter if so much oil came out from the aft seal.

So I cleaned all the oil, checked to make sure the oil tank was properly vented and ran the engine today for half hour or so. I did not see any oil leaking. I am going to run it a little more and try to get my borescope in the flywheel area to see if I can see more oil. 

How do you go about finding the source of a leak like this?

Best Regards,

Chris

 

  • Re: Oil leak aft section

    by » 5 months ago


    Wise, IMO, to check for crankcase cracks as specified in AD 2010-20-23. Also wise to check venting. A twist for this time of year was an separator on a vent line for my old O-200 Citabria which would ice itself closed when running in freezing weather, pressurizing the case and blowing oil "everywhere".


  • Re: Oil leak aft section

    by » 5 months ago


    Thanks for the feedback Jeff. I read the SB and it doesn't apply to my engine (mine is newer). But regardless, I walked out and checked the areas in the crankcase and could not see any cracks or evidence of oil seeping out on those areas.

    I have been told by a few people to ensure that there was not a possibility of crankcase overpressure. I checked the tank's vent line and it's clear. I am here in Florida so I would think that icing on the vent tube would not be an issue even in this time of the year. I also checked the oil return line to the tank and has no kinks.

    My indicated oil pressure is 60 psi at start and drops down to around 45 a few minutes after start. The engine has 100hrs since rebuilt by an iRMT Repair Centre (complete teardown but no crankshaft replacement). Engine was first placed in service March last year.

    Right now, I have not seen any more oil leaking (ground runs only). I will continue to run the engine on the ground to see if I find any oil. If not I will have to take it up for a flight within reach of the airport and see if an oil leaks.

    Best Regards,

    Chris


  • Re: Oil leak aft section

    by » 5 months ago


    Chris - as a veteran of several aircraft engine oil leaks, here's my 2 cents:  You obviously know it doesn't take much oil at all to look like a lot or make a mess.  But first, I would completely clean off the oil from everywhere, using something like 409 or that orange stuff.  Then I would burp and fill oil to mid flat part of stick - ensuring you didn't overfill.  I would add the yellow dye from the local auto store/blacklight/yellow glasses.

    You also know in flight with plenum pressures, oil can go in streaky directions, and left and right and up and down.  So I would stick with ground runs, and lower rpms.  If there is a way to prevent prop blast going into the engine area, blowing oil, you could look at that as well, but that isn't 100% important.

    Anyway, add the dye, and run the engine for 5-10 min keeping an eye on temps.  Then shut the engine off, close the hangar door and snoop around with the blacklight.  You should immediately see where the oil is coming from.

     

    Bert


  • Re: Oil leak aft section

    by » 5 months ago


    Thanks for the feedback Bert,

    Good advice and I concur with what you say. I am aware of migrating oil (as an A&P had to deal with that and had a few interesting experiences in my 40 years of flying). A couple of things do stand out in your comment:

    1.- My oil is to the top of the flat section of the dipstick. Could that cause a problem like this in this engine?

    2.- Is the use of a dye in the oil safe?

    3.- On my last oil change I used the Tempest oil filter. Have people found having any issues with it?

    4.- I just had an issue where coolant got into the oil. I fixed the issue, drained and changed the oil. I wonder if any leftover coolant in the oil could cause an issue like this (such as clogging in the oil filter or blockage)? Oil pressure readings have been normal so I didn't figure all is OK.

    Best Regards,

    Chris


  • Re: Oil leak aft section

    by » 5 months ago


    Hang on... your oil is at the top of the flat section after you lost a bunch of oil??  

    Sounds to me like you might have had an overfull condition and now you no longer do, because the excess oil blew out of the oil tank vent.

    One way this can happen is if you forget to burp the engine before performing an oil change.


You do not have permissions to reply to this topic.