787 oil in crankcase (passes rotary pressure test)

[tingraham]

Morning folks,
working on a 787 this morning and was about to be pulling the engine to put a crank in because of oil filling up crankcase. I decided to run a pressure test before pulling the motor and the thing is holding 14 psi for like 30 minutes now. Has anyone seen the oil injection leak and cause this before?

 

[etemplet]

Where are you applying pressure. 14psi seems pretty high to me. I would not do more tha 5-7 pounds. I recently tested an engine and found a leak along the parting lines for the rotary valve. It would be better to remove as much of the oil as you can so that you are AIR testing the chamber. It will be a more accurate test. Good Luck !!

 

[mikidymac]

Only use 8 psi or you can blow the seals out.

You can still be leaking oil from the inner crank seals.

 

[AKnarrowback]

My 787 passed the leak down test but still had inner seals that let oil through.

Is there oil in both cylinders or just one?

My 787 had the mag cylinder only leaking, pto was dry.

If both are filling up the both inner seals could be leaking. But, like was shown with the bubbles, a case seal leak could be happening. It's rare but would be putting oil into both cylinders. Pull the RV cover, clean and dry things on the cases, let it sit overnight with oil in the RV chamber and see if there is a leak.

Either way you have to take the motor apart to fix it. If the motor has some miles on it I would do the crank regardless of the findings. Rotax RV motors are great units except for that five dollar seal built into that crank.

 

[tingraham]

Alright folks, thanks for the input. I’m aware the manual says 5psi for testing the rotary chamber, but that wasn’t budging so I thought I might as well push it a bit further just in case. Absolutely zero pressure loss. It is an SBT engine, only about 4 years old. I ended up pulling rotary valve cover and testing the check valves. The PTO check valve was definitely acting lazy (which is the cylinder that was full of oil). When applying pressure going into the check valve (not reverse) the mag check valve would hold a few psi before releasing. The PTO check valve would hold a little and then hang open and only hold maybe 1 psi if that. I compared it to a spare cover I had in which both acted like the mag side on the original. Got everything back together and got the oil cleared out. At this point all seems to be well. Time will tell if it is permanently fixed.