Provent oil seperator boots.
After days of cleaning and inspecting, its looking like the oil pump lost some pressure, of the 11 screws and two bolts fixing it, 2 where missing another 3 hanging on by a couple of threads , another 4 where down but loose and only the 2 bolts and 2 screws, all in a row at the bottom of the pump were tight. The top of the pump had come away and I could slide a feeler guage under it, so not sealing. I think it was still pumping but had lost some pressure. Oil was probably still getting around the engine and up to the head and gravity doing its work from there. However at the bottom of the block, beneath each piston is an upward pointing piston oiler tube. Oil should shoot up out of these under pressure and lubricate the piston and rings. The pistons have oil gallerys in them that go up to the rings to keep then oiled.
Piston 3 had rings jammed in piston (why I had next to no compression in 3), and wear on the sides below the rings and piston material on the cylinder walls. Piston 4 (the one that is stuffed) has a a lot more wear on the sides and piston material smeared down cylinder walls, much more than 3. I initialy thought the bores were scored but it looks like it just a layer of melted piston.
The piston oilers for 3 and 4 are at the end of the oil line. Pressure could have dropped enough so that oil from the piston oilers on 3 & 4 wasnt reaching the pistons.
The rest of the engine looks well lubricated. Bearings and head dont look like they've been running dry.
The alluminium from piston 4 that melted and disintegrated then found its why into everything, the ports on the head (Cyl 4) and the exhaust manifold look like they have been sprayed on the inside with a layer of liquid aluminium. This has then gone from the exhaust manifold into the turbo and its inlet is full of it and siezed.
Ground up piston in sump and throughout engine, however because its soft it doest look to have done any damage to crank or cams etc.
The 2 missing screws were found in the bottom of the motor mashed up and these have damaged one of the camshaft drive gears and the idler gear that links the 2 camshafts.
No obvious sign of how coolant got into oil, either heat warped the head or in internal crack I cant see. Have checked head for flatness and is within tolerance, no damage to head gasket.
Read nissan manual up on the oil pressue light and this only comes on when pressure is near zero.
The point where the pump lost just enough pressure not to lubricate the back two pistons would happen very quicky, its not that they would be getting oil gradualy less and less. One second they are getting oil the next there not, and with the pistons doing 2000 odd rpm things go downhill quick.
From what Ive read, loose oil pumps bolts is a problem on the first CRDs and some failed early and got new engine under warranty.
Should have been a recall for this! But can you imagine them recalling every patrol for an engine out and stripdown to check and torque down properly.
Out of interest no sign of loctite on bolts.
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