I started getting smoke from the exhaust recenlty, it worried me because I thought the turbo was letting go.
When I check it the compressor shaft was worn and it had been hitting the casing, so I swapped it for a brand new core.
Once run in I started to drive it normally and started to get the smoke, in fact worse than ever
To cut a long story short it turned out to be the crankcase breather
these have a valve inside to prevent the turbo sucking oil out of the crank, it shuts off when the turbo is sucking hard. This valve was blocked somehow and the engine pressure caused by worn rings was starting to blow oil out of the filler cap. When it got really bad it was blowing back into the turbo drain pipe and pressurising the turbo oils seal which then leaked.
I thought it worth posting as I've never read about this anywhere and yet it could have caused a runaway engine. Just goes to show that sometimes it's a simple fix, although the turbo was worn it wasn't the cause of the smoke at all.
