zogster

I've just pulled my cylinder head in order to change the gasket - still had coolant in my oil after an oil cooler seal change - and I'd like to know what its appearance says about how the engine has been running.

But I really don't know enough to read the signs... at first glance it seems clear that one cylinder (2nd from left in the attached pic) has been doing something different and has more oily deposits compared to the other cylinders. (The injector for this cylinder also appeared dirtier and greasier than the others.)

Can anyone read anything into this pic?

944meister

The white on the valves is a sign of running lean. Its hard to tell if that is burnt oil buildup or carbon buildup and/or mixture of the two. What mileage is on the engine?

zogster

Many, many happy miles on the engine ;-)

About 208,000 in fact - though only 15,000 or so since the head was last off for a new head gasket.

zogster

And here's a CU of one of the three chambers with white deposits.

944meister

It looks primarily like a lean mixture with carbon build-up in the zoomed in photo. The white ceramic on the spark plugs should turn to a light tan color with good air/fuel mixture. If you do suspect a bit of oil getting into the combustion chamber, its most likely bad seals on your air oil separator. This would cause a lean mixture and also let in oil into the intake. An easy way to check this is to just look at the inside of the intake manifold for oil. Obviously, there can be a mixture of a few other things that could cause a lean oily mixture though, worn valve guides, worn piston rings, a vacuum leak elsewhere in the intake, ect.

zogster

Thanks - I'm pretty sure that I do have a bit of a leak at the AOS, so I'd put that at the top of the list for likely causes of a lean condition.

I'm in two minds as to whether to change the seals however. I gather I'd have to remove the turbocharger to do it, which looks like a fair bit of work. I'm more inclined to get the head back on and get rolling again, then do those seals along with maybe oil pan gasket and motor mounts when the days are longer and the weather's not so miserable.