Hydraulic lock

by Robert Musgrave in 912 / 914 Technical Questions 14 years ago

A friend went to start his 912 ULS at weekend and found it would not turn over. Eventually we got it to, but oil ran out of the exhaust of No. 3 cyl. We removed the head and cyl. and measured the ring gaps. they are just under the specs. at about 80% wear. the engine has clocked about1500 to 1600 hrs. Has anybody had this problem?

Robert.

Re: Hydraulic lock

by Roger Lee » 14 years ago

Roger Lee

131 5.38k 5.44k

Hi Robert,

This is one reason to turn the prop over by hand first to check the oil. If you have a hydra lock you will know. It has happened in the past and it's one reason Rotax made a major change to its oil filter. Not everyone mounts the oil tank at the proper height in relation to the engine.
Excessive wear can cause this. Mounting the oil tank too high above the recommended can cause this. The new oil filter out by Rotax will help prevent this situation with it's now anti drain back valve and check valve.
If the rings are worn past the allowable limits it may be time to service the engine. Usually the rings and top end will make TBO if you use a good synthetic oil, don't use 100LL, change the oil when you are supposed to and "do the regular maint items listed in the "Line Maint" Manual on the engines 100 hr. inspections." Following th3e regular 100 hour maint inspections and recommended timed maint. can save big money down the line.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

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Re: Hydraulic lock

by Robert Musgrave » 14 years ago

Robert Musgrave

5 3 0

Thankyou for the answer, You have confirmed just what I was starting to suspect, namely the oil filter as I have now noticed that the oil is starting to syphon into the crankcase. I also noticed the engine is fitted with a non standard oil filter.
Regards, Robert.

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