18K4F / 16K4F

Rover's K-Series — the 1.4, 1.6 and 1.8 — in the Freelander, MGF, Rover 25/45/75 and the Lotus Elise S1.

⚑ Its head gasket failure is the most notorious in this catalogue, and the cause is structural rather than a bad part. The engine is built as a sandwich held together by long through-bolts running from the head to the main bearing ladder, with wet cylinder liners in between. The whole stack moves with temperature, and once the gasket goes it goes quickly.

So overheating is not a symptom here, it is the mechanism. A single serious overheat can end an engine, and coolant level and the header tank cap are not routine maintenance on a K-Series — they are the failure mode.

The tell is coolant loss with no external leak, then oil emulsion under the filler cap and pressure in the header tank. A chemical block tester answers it in ten minutes and before anything expensive is ordered.

The accepted repair uses a multi-layer steel gasket and revised dowels, not the original composite one — a like-for-like replacement fails again, which is the single most useful thing to know before quoting one.

The KV6 six-cylinder is a related design with its own page here and its own version of the same problem.