Approximatley one year ago I resolved a 912 push rod tube oil leak at the head-tube intersection with 3M Fire Barrier 2000+ silicone caulk.  The low pressure oil leak slowly got bad enough that I either had to remove the cylinder head and correct the problem or find a quick fix.  I flushed area with MEK from a syringe to remove all oil and grime residue and then applied the high temp silicone with an ear swab (difficult area to access).  There are still no signs of oil leakage after approx. 1 year.  I also corrected a small case leak immediately posterior to where the vacum pump mounts.  This particular grade of silicone has structural properties similar to RTV (some times labeled as Aquarium Cement).  Air Spruce is a supplier. Dave Weaver N912GR --- On Fri, 3/11/11, GRAHAM SINGLETON wrote: From: GRAHAM SINGLETON Subject: Re: RotaxEngines-List: 912 ULS oil leak To: rotaxengines-list@matronics.com Date: Friday, March 11, 2011, 6:02 AM Remi I think you will need to split the crankcase and check inside. We did this once and fitted new O rings which cured the leak (same symptoms as yours) Either a crack has developed in your  case or it has got O rings which have failed. Cause of failure is fretting of the crankcase joint. Just like Lycomings do. Graham From: Remi Guerner To: rotaxengines-list@matronics.com Sent: Friday, 11 March, 2011 10:30:10 Subject: RotaxEngines-List: 912 ULS oil leak --> RotaxEngines-List message posted by: "Remi Guerner" Hi all, My engine has developed an oil leak on cylinder 4 which has grown to the point where it must be fixed now. The leak is located at the junction between the cylinder barrel and the cylinder head. See attached picture. According to our Rotax distributor, the oil is coming from the crankcase, then it flows along the cylinder studs and escape between the barrel and the head. He does not know how to fix it. My crankcase P/N is 888364 and S/N 22031. The relevant drawing of this crankcase assy is page 5-2 of the May 2010 IPC. The drawing shows that there is no gasket nor o-ring to provide a positive seal between the studs of cylinder 4 and the crankcase. I have studied SI-912-019 R1 which talk about oil leakage in the cylinder area, but this SI affects crankcases from S/N 60010 only. The design of the crankcase has been changed extensively. Therefore this SI is not applicable to my crankcase version. My question:  has anyone experienced this sort of oil leak on the old crankcase version (crankcase S/N below 27811) ? How to fix it? Regards Remi Guerner Europa F-PGKL Read this topic online here: http://forums.matronics.com/viewtopic.php?p=333515#333515 Attachments: http://forums.matronics.com//files/p3090011a_177.jpg http://www.matronics.                     -Mats.com/contribution" target="_blank">http://www.matronics.com/contribution==============