Good old blow by, and I know it well.
I was posting some answers to a Boxhead question over on the Rattle thread and put up some photos of the end result with this condition.
The reason why this happens : Basically, the seats (sheets) fail and the exhaust gases mix with the engine oil. This in turn causes a chemical reaction which turns the engine oil into solid material, which blocks the sump screen and starves the block of lubrication. NO LUBRICATION = NO BLOCK, PISTONS AND CRANKSHAFT.
This is an expensive repair and should be avoided by educating yourselves.
As what has been pointed out on this important thread, the screen should be checked at every oil change service. I recommend the 5,000km interval service, mainly because the EGR system hasn't changed that much in design from the late model 1KZ-TEs, and they were 5,000km intervals.
These are the seats that cause the problem when they distort, especially the old copper seats that had not been coated. Late 2007, TMC redesigned the seats, and that lead to the seat on the right. The cooper seats have been deleted from the parts catalogue worldwide. 30011 is the new number, the old one was 30010.
In Australia we had the situation where a lot of dealerships did the valve clearance by audible means. My personal opinion on this was to keep the price down in line with fixed price servicing which most of us outside of Toyota Service cannot compete with.
In GSIC, it specifically states that the injector sheets (seats) should be replaced with the valve clearance services under warranty at the 40,000km and 80,000km services.
Unfortunately, this was not done to many vehicles which lead to this problem being common place. Well, at least in my world, and other diesel fitters who are members of the AADS.
Some people get mixed up with the seal, which is an O ring type half way up the injector shaft. You can see on this photo that the blow by has taken out that seal. All the seal does is stop the engine oil leaking out of the injector port, as there is an outlet within the cylinder head that allows engine oil into the port to help cool the bottom half of the injector. The seats are there to block off and seal the hole where the injector nozzle goes through on the cylinder head and thus the block bores.
The Roo.
Passing through country and seeing country are two different things.