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Purging oil after line replacement

seagull

Well Known Member
I am adding the thermostasis which involves 4 new oil lines. The instructions say to purge the lubrication system per SI-912-018. There is a requirement in SI-912-018 to pull the valve covers and check all lifters for air, is this necessary with an engine that has been in service?
 
I believe there's a requirement to run the engine at 3500 rpm for a set time to purge any air from the lifters if there was some excessive rocker arm clearance
 
Yes

Even for an engine that has been in service, the instruction says to do the procedure completely if air has been introduced into the system, including due to changing oil lines. I guess it is a hassle to check that the lifters have been properly purged, but that's what they want us to do.
 
I believe there’s a procedure to apply 3 to 5 psi of regulated air to the oil tank while turning the engine by hand, but I done have my rotax manuals in front of me..
 
Thank you everyone for leading me to the Rotax info / requirements, that was not my question. What I was asking in the original post was if someone knew a work around for removing the covers and incurring the cost of the expensive gaskets (which Rotax also suggests replacing).
 
Ok, so this is what I learned in the Rotax course at Lockwood…. If after the oil purge the rocker arms have some give, run the engine for a period below 3500 rpm, as mentioned earlier. Repeat if still soft. What this tells me is that running the engine would push any air from the lifters, since the was no other remediation solution offered. But this would not negate the need to perform the initial purge. And I specifically asked about replacing the o-rings. The answer I got was that it’s not always necessary. So, I’d say depending upon the amount of time on the engine, it may not be necessary if you performed a long enough ground run and do a good job of checking for leaks after replacement. Anyway, that was my take away. I’m sure others on the forum took the same course and can weigh in from what they learned.
 
Yes check the lifters. Also check the valve cover gaskets for any damage and if they look good reuse them. Then check for any leaks around those gaskets after running the engine. If no leaks then you are good to go.
 
Bob Y, I think you said it the way I have been thinking. I was looking for actual experience with the exact issue. Others telling me what the purge instructions say is of no practical help.

The question;
After purging with the compressed air you then run engine @ 2200-2500 for 7 minutes and check the valve tappets, (actually hydraulic lifter is where the air would be trapped). If one of the 8 is soft then run the engine again and recheck. The test run and recheck can be done a total of 3 times. Rotax expects that a few successive short runs will purge a healthy lifter, if it doesn’t recover then it had problems before the work was started.

My opinion;
If the lifter doesn’t recover after 3 test runs then it probably wasn’t working correctly before the purge. If that is the case then checking the tappet clearance should be a regular maintenance item, failure can occur any time. I can’t imagine how a lifter could fail by getting air in it while not moving and still inside the lubricated environment of the engine.

In any other engine when the tappet clearance is out of spec whether from mechanical adjustment or failed hydraulic lifter, the engine performance is reduced. I am surprised this isn't mentioned by Rotax.
 
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