Originally Posted by jmfitzger

The assumption is that there is a leak along the #1 cylinder seal of engine #235(my engine). After the breach and during each ignition when the #1 cylinder pressure can exceed 1000PSI at full throttle, combustion gasses are now forced through the breach. So these 1000PSI pulsations pressurize the oil galley or gallery or whatever it is called - the long cast-in and cross drilled oil channel that runs right next the #1 cylinder seal for about 3 inches.

The oil system, or a portion of it, might well be receiving a 1000PSI pulse every other rotation of the engine. These hydraulic pressure pulses could then be pushing on seals designed to hold peak oil pressure which would be somewhat less than 1000PSI. Furthermore, the loading would be fatiguing

A few possibilities come to mind:

1) Secondary seal breaches are causing oil suspended in now excessive gasses in the cam cover to be forced through the blow-by tube into the turbo inlet. (the crank case , chain tower and cam cover are all one open volume)

or

2) Secondary seal breaches of the oil system are somehow injecting oil into the intake system

3) High pressure exhaust gasses leaking from the primary breach are forcing oil to unanticipated places and/or in larger than anticipated quantities and getting into the cyclinders.

and

4) At some point cyclinder #1 begins to draw oil in and it accumulates faster than it is burned and expelled.

According to research done recently for SwRI, these are the most common failure modes for heavy duty diesel engines:

1) Cylinder head cracking
2) Combustion seal leaks
3) Cylinder block cracking
4) Excessive wear of rod or main bearings
5) Piston pin or piston cracking
6) Crankshaft failure

"Bent rods" dosen't even get honorable mention.

I do not understand how enogh oil can come up from the bottom of the cyclinders and get past pistons to loose 2 quarts of oil in 45 minutes at idle. I do not think enough oil can come up past the piston to burn blue smoke unless the piston has a hole in it or a broken ring or skirt.

I like the idea of oil related hydraulic overload for all of these 3.5 liter 603 rod failures. In the oiling system first, and then if you don’t catch it in time, rotation through TDC oil lock. Typically, diesel engines are designed for infinite life byusing a safety factor of about 1.5, and the peak load safety factor of about 2.0. That means each cycle could experience a 1500PSI load with no fatigue. It also means that the occasional 2000PSI lock should not break anything. Where can I get injectors or glow plugs with built in relieve valves?

If the cylinder seal begins leaking combustion gases first and then only sporadically, the leak would only be a gas leak into the oiling system. This would also mean that the cylinder seal ring would be subject to unusual stresses at each ignition. It would then be subject to unexpected fatigue loading and could work its way loose over time.


If my guessing is correct, then there is clearly a design/manufacturing flaw. The enlarged cylinder bore took thickness away from an already thin wall between the oil channel and the cylinder. When the tolerances stack up for size and location of the head, the oil channel in the head, and its wall thickness, the diameter of the cross drilled holes and their location, the location of the cylinder bore, the size and location of the head gasket and its seal, etc. It seems more than plausible that this is were the design limits were exceeded. When it all stacks up in your favor, the engine will go for 500,000 miles. When the inspector pinches a bit of molding sand in his micrometer and passes a too-thin head, your engine goes for 80,000 miles.