914 Oil Seepage From Airbox Intake Tube

I should add that not long ago someone said they saw a puff of white smoke on takeoff.. 

Hi Craig

White smoke on takeoff suggests your turbo is flooding oil while you sit.  The turbo will push this into the airbox and cause the oil in the vent as you have noted and the white smoke.  The fitting just at the terminal where the oil is pumped into the top of the turbo has a small check ball and spring.  This is the most likely source of your problem.  The banjo bolt that holds these parts and the ball have carbon on them.  In addition remove the oil tank from the bottom of the turbo and clean any carbon buildup from inside if any.  Hot engine shutdown is the most likely long term issue.  Be sure to cool the turbo after flight by prolonged taxi and idle to allow oil cooling.

Cheers

I assume if I do either of those I need to purge the oil system afterward?

Craig, yup.  Not worth the risk.  

Do the purge and as a final bit remove the line from the turbo oil return at the oil tank and check to make sure you have good flow back to tank from the scavenge pump. 

Cheers

I looked at how to get access to the banjo bolt at the top of the turbo and it is extremely difficult to get in there, so I'm worried that I'll have great difficulty getting it back together.

Can I run the engine with the top cowling off and watch whether I still have a problem before trying to fly it to someone who really knows what they're doing? Could I just look for any white smoke and any oil escaping from the airbox intake tube? If nothing appears then I'm fine to fly?

Any other symptoms I could check for to ascertain whether I still have a problem and I shouldn't fly?

Anything that I could add to the oil to clear up any blockages?