A clean fuel filter would imply the injector o-rings were good; the fuel passages are between the coolant side of the cups and the HPO side. Only the bottom injector o-ring seals within the cup, the upper ones seal within the head itself. A cracked cup can leak coolant down into the cylinder when the engine is off. I don't see how a cup failure can get coolant into the crankcase - with a clean fuel filter.

The oil cooler can fail both ways, oil into coolant when running - 50psi oil versus 16psi coolant - and coolant into oil when shut off - 16psi coolant versus 0psi oil. I suppose the big o-rings and any pinhole leaks in the cooler itself could act as check valves and only leak in one direction at first.

 

Sure looks like the oil cooler to me. I can't see that much coolant getting where it shouldn't be through a cracked injector cup. Removing the injectors wasn't necessary and is going to cause you a lot of extra work. While you have them out (you may as well pull the other side now too) change the o-rings on them (with Alliant o-rings only) an replace the glow plugs (with Motorcraft plugs only). Also make sure you have an in-lb torque wrench. You will want to hot-torque the injectors on re-installation as well.

How old is your water pump? Now is a good time to replace it since you have to drain all the coolant out of the motor to change the oil cooler. Make sure you get new o-rings for it too.

 

I've done the oil cooler on my idi. They look similar. Explain hot torque for the injectors.

 

Well after making a plate to bolt to block with view holes cut to watch, and applying a little pressure to cooling system, there is a pin hole in front driver side cylinder. Well crap. I thought it was just the idi motors that had this problem. It's plain as day no denying the stream of water spraying from the cylinder wall.

 

A plate to replace the cylinder head? With holes to see inside the bores? Good thinking. Sorry to hear about the bad block.

 

That is a terrible prognosis, sorry to hear about it.

 

Cavitation/"block worm" is an inherent problem in nearly ALL diesels. It has to do with the high frequency vibrations generated by the compression ignition combustion process. I'm not sure if it is still an issue for modern passenger car diesels, given their vastly improved "smoothness", but it is definitely a problem for "heavy duty" diesels like our 7.3s

Basically, those vibrations generate tiny little micro bubbles in the coolant, and when the IMPLODE ( not EXplode), if they are in contact with the cylinder wall, they eat away a teeny tiny few little iron atoms. Overtime, it adds up, until in a particular spot, there are no more iron atoms left, and poof you have hole.

Coolant additives ( whether the SCA type we have to monitor and add to older coolant or the included OAT type "stuff" found in the newer ELC coolant) don't actually stop that process. It pretty much can't be stopped, as it is inherent to diesel combustion. Instead, they leave a protective "sacrificial" layer on the cylinder walls. So, that layer "takes the punch" instead of the actual block material


Did your friend use the proper coolant, and regularly monitor and maintain the SCA additive level ( or switch to ELC coolant which has such a long service life, in our trucks its basically lifetime coolant)? If not, that's what lead to the block failure.