The brief
The S350L came in for routine servicing, the owner wanting the whole car looked over rather than just an oil change. There were also small signs of an oil leak, a faint burning smell and a touch of residue around the engine, so that got particular attention in the inspection. A proper service runs through the whole car: change the oil and filter, replace the air and cabin filters, check the fluids, look over the brakes, suspension and electrical side, test the battery under load, run a diagnostic scan, and eyeball the belts, hoses and underbody, including the engine seals. Done right, it's exactly when a small oil weep gets caught and dealt with before it spreads.
The diagnosis
The visual and diagnostic check went through the lot. The engine oil and filter were due, the air filter and cabin filter were at the end of their life, the brake fluid's water content was a touch high, and the battery was beginning to slip on the load test. And the oil weep traced to a hardened seal at the camshaft area, weeping a little and giving the burning smell. The belts, hoses and underbody were otherwise clean, no fault codes stored. So it was a full-service list plus resealing the camshaft area: replace the wear items, freshen the fluids, fix the leak, and note the battery to watch.
The work
The engine oil was drained and refilled with the correct Mercedes-spec oil and a new oil filter fitted. The air and cabin filters were replaced, the brake fluid bled and refilled, and the battery load-tested and flagged. The hardened seal at the camshaft area was replaced with a fresh genuine Mercedes-spec seal, the mating face cleaned, and the oil residue cleaned off. Coolant and washer fluid topped up, and a full diagnostic scan run. A road test confirmed everything was running cleanly and there was nothing weeping.
The outcome
A full clean bill of health on the S350L, with the camshaft-area seal sorted and the engine bay dry. No flags left except the battery to watch, and the car back on the road for another interval. A service is the cheapest insurance there is, and catching the oil weep during the inspection meant it got resealed before it spread or dropped the level.
