The engine in question is the 4.7-liter M278 bi-turbo V8.
Without regular maintenance, there will be consequences for any engine, and Eric from I Do Cars showed us the dreaded effects of high temperatures by tearing down a dead Mercedes-Benz V8.
Eric got a hold of the 4.7-liter M278 bi-turbo V8, the predecessor of the M178 found in the Mercedes-AMG GT. Making more than 400 horsepower, the expensive V8 was sourced from a 2013 ML 500, which we know today as the GLE-Class.
Not many details were known about the engine, including mileage. There also wasn't a significant sign of overheating right off the bat. However, when Eric turned the crank to see if the engine was locked up, he had to exert extra effort, suggesting the issue might be found in the internals.
After removing the air boxes, high-pressure fuel lines, and intake manifold, Eric discovered that the back of the valves looked terrible, describing them as "some of the crudest intake valves" ever seen on the channel. Fortunately, the Honeywell turbochargers were both in excellent condition.
With the forced induction devices out of the way, the valve cover was removed from the engine. Here, he saw minimal damage on parts of the camshaft assembly. The other half of the assembly looked a bit better.
Before taking out the camshafts, Eric removed the oil filter, which had a leaf and some bits of metal. How did they get there? We are unsure, but the camshafts and their journals didn't look too bad. Removing the said components meant the cylinder head could be disconnected from the block.
This was where Eric found the major issue, as the cylinders showed bad bore scores. After removing the oil pan, timing components, crankshaft assembly, and pistons, the parts look salvageable. Considering the significant marks on the cylinder walls, it's no surprise that some of the pistons showed skirt damage.
Eric concluded that the owner might've run the engine hot for an extended period of time, expanding the pistons that damaged the cylinder walls. The issue is down to human error and not necessarily bad engine design. As is so often the case, a regular oil change and some mechanical sympathy could've saved this V8 mill.