purging of lubrication system
in 912 / 914 Technical Questions
14 years ago
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Re: purging of lubrication system
by Rob Seaton » 12 years ago
Some history: the reason for AD-2002-21-16 (now rescinded and replaced by AD-2005-01-14) is a certain influential but misguided person was telling customers and maintenance shops to blow out the oil cooler and oil lines with shop air and to rotate the prop backwards with the oil filter OFF every oil change!! (to pump all that dirty oil out of the engine)
He believed this was the best thing to do during an oil change. He was wrong and 3 inflight valve failures resulted. Basically the engines were experiencing a dry start every 50 hours.
The FAA demanded strong action to prevent this from happening again. The first AD did not allow the prop to be rotated backwards, even an inch! Also the purging had to be done every oil change!
Of course this is an over-reaction, normal turning of the prop backwards does not harm the engine and normal oil changes will not introduce enough air in the lifters to cause any harm.
So now with this knowledge we know that as long as you follow the Line maintenance Manual oil change procedure and do not introduce large amounts of air into the lifters you will be fine. We also know that the small amount of dirty oil left over after every oil change in not to be worried about, you will get it next time! (and if you oil is really that dirty you need to change it more often)
This is a very short version of all that took place back in 2002, we also had people starting engines for the first time without any purging, using anti-dispersant (AD) oil, diesel oil and silk thread on sealing surfaces so the general knowledge of the Rotax engines has greatly improved since then.
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Re: purging of lubrication system
by Przemysław Wiśniewski » 12 years ago
Hi.
How to make purging when I have thermostat installed before oil cooler?
It's closed when cold so oil can't fill cooler.
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Re: purging of lubrication system
by jan kerstens » 12 years ago
Hi,
I have also installed a thermostat myself and did an oil purge. There is always some leakage in the thermostat even when it is cold. It will take more time: rotating the prop. Very important is to check the tappets of each cylinder. They should be hard and if not you have to rotate the prop more: displacing more oil.
Jan
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Re: purging of lubrication system
by Przemysław Wiśniewski » 12 years ago
Do you replacing valve covers gaskets after checking?
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Re: purging of lubrication system
by jan kerstens » 12 years ago
No, I have inspected them and found that they were in good shape (note: the ROTAX912UL had only ca 150 hours).
Another remark. In view of the fact that the thermostat when cold has only a very small leak the temperature of the oil needs to be relatively high. Therefore purge the oil in a warm working place or in summer.
Good luck!
Jan
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