This has me stumped. My Sigma has been running great and trouble free for years. The timing chain was getting a bit rattly so I fitted a new pump, chains and sprockets. Rattle gone.
Not long after ( I am putting this down to coincidence) I took the wagon out of the shed for the daily macca's run. Backed out into the street. Slight uphill for about 150 metres to a little roundabout. Changed back to second gear for the roundabout, a bit of go pedal on exit (as I have done for the past 10 years)...and a blue oil smoke screen followed me for about 200metres. Immediately swing around,drove back home and put it in the shed. Thinking the worst, I lifted the bonnet looking for obvious signs of trouble, but could not find any. Oil level was correct..the carby damper was still full, no oil leaking onto the exhaust anywhere. Thinking valve stem seals..oil control rings I ring my mechanic mate for advice and he says bring it around. So I backed it out again, drove to the roundabout again..and NOTHING. No smoke..where as 30 minutes before it layed down a smoke screen. And I drove it around all day without further drama's.
And so it has been for the past week..oil smoke at the roundabout first thing in the morning, and nothing for the rest of the day.
We have basicly ruled out rings and valve guide seals because when I take it to my favourite test hill I can hold it with compression all the way down (about 1.5klm) and there is no smoke when I get on the gas to go up the other side.
Sort of leaning towards a turbo carbon seal issue , but it is still weird that the problem only exits on initial startup in the morning, and it takes the vacuum created by going back to second at the roundabout to suck the offending oil into the intake cycle. Too much oil pressure ??
Open to online diagnostics
