Engine oil and coolant are the interrelated lifeblood of the 6.0L Power Stroke. If a clot should form, preventing flow, or the fluids become mixed, severe damage can be done to the injectors, high-pressure oil pump (HPOP), engine bearings, heads, turbo, block, and pistons. The symptoms to watch out for include: steam coming out of the exhaust pipe, the puking or unexplained loss of coolant from the overflow bottle, and coolant or sludge in the intake manifold when you remove the EGR valve. A thick, black ooze in either the engine coolant or oil systems and internal sections of the intake manifold that look like they've been steam-cleaned is also a sign that something is wrong. The factory liquid-to-liquid engine oil cooler (EOC) situated on top of the 6.0L directly below the oil filter is prone to clogging because the internal coolant passages are narrow and BulletProofDiesel (BPD) says the 6.0L requires 181/2 gallons of cooled oil per minute at peak demand. BulletProofDiesel's solution is to replace the factory oil cooler and filter with a remotely mounted air-to-liquid cooler and spin-on filter. The other line of defense is an upgraded EGR cooler. This operation turned an '03 Ford into a reliable diesel truck that still has functioning emissions equipment. This isn't the first time we've operated on one of these potentially reliable engines; for more critical information see "Every 6.0L Problem Solved," in the July '09 issue of Diesel Power magazine.