The brief
Mr Kenneth brought his 520i in for some oil leak rectification not long after the warranty ran out, which is often when these things surface. Rather than chase one drip at a time, the job was to find every leak and seal the lot in one visit. Over the years the seals and gaskets around the engine and the back of the gearbox harden and lose their grip, so oil weeps out. On this car there were a few: the oil sump gasket weeping where the sump bolts to the block, and at the back, the flywheel oil seal and the torque converter oil seal both leaking, which on this layout means the gearbox has to come down to reach them. Hardened seals don't reseal themselves, so each one gets renewed properly.
The diagnosis
The inspection found three leaks: the oil sump gasket weeping, and the flywheel oil seal and the torque converter oil seal both leaking at the back of the engine. The rest of the engine was sound, just the seals and gaskets gone with age. That's an oil sump gasket replacement plus the flywheel oil seal and the torque converter oil seal renewed, which means dropping the gearbox to get at the rear seals, rather than chasing the drips piecemeal.
The work
The oil sump cover came off, the old hardened gasket removed and a new genuine BMW-spec sump gasket fitted, the mating faces cleaned and the sump torqued back down to the manual figures. The gearbox was dropped down to reach the rear seals, the worn flywheel oil seal and the torque converter oil seal replaced with genuine BMW-spec seals, and everything reassembled and torqued to spec. The oil level was checked and topped, the area cleaned of old oil. A road test and a check on the lift confirmed the engine and gearbox dry, no drips, the levels holding, and no warning lights.
The outcome
No oil leaks, the engine and gearbox dry, no drips on the driveway, the levels holding, and no warning lights. Mr Kenneth got the 520i back sealed up. Doing all three leaks in one visit, including dropping the gearbox for the rear seals, was the sensible call, because the rear seals only get worse and you don't want to be back in here twice.
