Engine seals

Category: 912 / 914 Technical Questions 5 weeks ago

I have oil blowing out the    the gear box and the firewall area  of an overhauled engine from a well known company with 30 to 40 hours on it. It started with minor leaking from the front gear box then started in the rear of the engine. Any Idea what could be causing it to blow throught the seals? The engine was stored for a few years have the overhaul . Maybe 6 or more the shop won't tell me the history.

When it was instaledl the oil system was modified with an extra oil cooler. Does anyone know what happens to the engine if it isnt purged and air got into the system?

I am having the seals replaced but what could be causing it?

  • Re: Engine seals

    by » 5 weeks ago


    If air gets into your oil system, your lifters can go flat which may result in the hammering of the valvetrain and damage to the lifter, camshaft, etc.

    Your crankcase pressure might be too high due to restrictions on the return side of your oil system. Excessive crankcase pressure can cause the oil to blow past your seals, OR you can have dried out cracked seals that are leaking? This can be difficult to diagnose without looking at your aircraft and engine installation. 

    In the attachment is the manual reference for the entire oil system. This section will show you how to check your crankcase pressure and see if your oil system is properly designed and as per the Rotax installation manuals. 

    27482_2_Oil System IM912_REV1.pdf (You do not have access to download this file.)

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