Purge after cleaning out oil tank?

by key dismukes in 912 / 914 Technical Questions 7 years ago

When i clean the sludge out of the oil tank do i need to purge the oil system afterwards? (I will leave the tank in place and remove the top and filter to get to the bottom of the tank.)

thanks,

Key

Re: Purge after cleaning out oil tank?

by Roger Lee » 7 years ago

Roger Lee

125 5.12k 4.53k

Hi Key,

I might catch some flack here so let's see.
You can answer your own question. Let's examine what happens during a normal oil change and or a tank cleaning. Some have to always take their tanks off just to do a standard oil change because of the engine/plane configuration.

So here we go.
During a normal oil change you burp the engine, drain the oil tank and change the filter. You never turned the prop during this process until oil was back in the tank and the filter was on. When you drained the tank all the oil came out and that included right up into the top two in and out fittings.
If you removed the tank for a cleaning and unscrewed these two fittings oil would not come pouring out. So if I took that disconnected fitting and either held it up high or placed a rubber plug in the end then I have lost no more oil whether it is a normal standard oil change or I was removing the tank. Now you pull the tank and clean it. Then replace both fittings. Since you have lost no more oil than during a normal oil change you could now fill the oil tank and vent the system. That means after the oil is in and you rotate the prop to make sure you prefill the oil filter and or any oil vacancies and you're good to go.

If you think this is in error then next time you do a normal oil change pull each fitting off and you might lose 1-2 drops of oil.

Here is the but part. If you lower these hoses and the ends are open and you allow all the oil to vacate these hoses then a purge should be done. The key is to not lose any oil over a normal everyday oil change.

Now some might disagree and that's okay and maybe they want to purge. Personal preference may come into play, but I would need some actual proof that you've lost more oil or injected more air than a normal oil change. After 20 years I haven't seen any yet.

Bottom line the choice is up to you.

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

Thank you said by: Pete Christensen

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Re: Purge after cleaning out oil tank?

by key dismukes » 7 years ago

key dismukes

15 11 6

Thanks, Roger. That was my thinking, but i really wanted an expert's perspective. By the way, you have been helpful to me a couple of times in the past, and i find it very helpful to read your replies to other Rotax owners.

Key

BTW a year or two ago i posted that my 912uls was not firing up as readily as it had in the past. Eventually i discovered that if i pull the choke out only 80% of the way (first start of the day) the engine always catches on the first few blades.

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Purge after cleaning out oil tank?

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