BMW’s S65 engine is among the most beloved of all of its engines throughout history. How does one not love a 4.0-liter naturally aspirated V8 that revs to 8,250 rpm? Well, there is one reason owners might not love it and that’s its reliability, or lack thereof. The S65 isn’t exactly unreliable but it has a few common problems that can cost owners dearly and you get to see exactly how bad it can get in this new video from M539 Restorations.
Sreten, the host of the channel, bought this E92 M3 Coupe with a six-speed manual knowing that it had a grenaded engine and even bought a donor car to borrow its engine’s bottom end. In this new video, he cracks open his coupe’s engine to see exactly what the damage is, how it happened, and what it’s going to need. When he finally gets to the bottom end of the engine—something that obviously requires an absolute mountain of work—what he finds is so bad the only reaction is to laugh.
The biggest issue with the S65 engine is its rod bearings. For some reason, BMW built the S65 with incredibly tight rod bearing clearances, which means if its oil isn’t sufficiently warmed before revving it hard, or the owner uses the wrong engine oil, the rod bearings can wear prematurely. When they wear too much, bye bye engine.
What happened to Sreten’s engine, prior to his ownership, was that two of the rod bearings slipped, as did the main bearing, causing too much heat, and the crankshaft actually broke in half. Due to the crankshaft snapping, the entire bottom end of the engine was toast and needed replacing. Thankfully, Sreten has the donor engine to pull from. Additionally, the head and valvetrain seemed to be in really good shape, and shockingly clean, so that didn’t need any sorting.
Interestingly, the rod bearings had already been replaced with upgraded ones, so them failing seems odd. However, Sreten reckons the main bearing failed first, which caused the crank to “go dancing,” thus damaging the rod bearings. Regardless of why, the entire bottom end needed replacing, including at least one piston. According to Sreten, it was the most catastrophic engine failure he’s ever seen. It actually makes me wonder if buying an E92 M3 is worth the risk, as it seems to struggle with internal lubrication and keeping its bearings from turning to dust.
