They're consuming coolant.

Early third-generation Ford Focus RSs have been suffering from engine issue that mean they consume coolant fluid.

Ford admitted to Autocar that early versions of the 2.3litre EcoBoost engine in the hot hatch consume coolant during cold running, leading to white smoke coming from the exhaust.

2016 Ford Focus RS: First Drive

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The company said they were 'working on a repair for all customers' according to a spokesman, adding, 'In the meantime, if vehicles show these symptoms, customers should visit their dealer for an inspection and repair under warranty.' However, an official recall has not been issued yet.

An official cause for the problem hasn't been confirmed by Ford, but owners have suggested that the head gasket is failing to seal the engine block to the head effectively, but the problem isn't down to a head gasket issue, but rather the block itself, which changes shape during multiple heat cycles. This in turn leaks coolant into the engine's cylinders when the engine is cold, causing it to burn and the engine to misfire.

Despite the base model Mustang also being powered by the same 2.3litre engine, it is not thought to be subject to the same issue. Thanks to its higher power output, the Focus RS' engine is built differently  its block and head is built using an upgraded alloy with a cast-iron lining and has a different head gasket design.

The Focus RS is a serious piece of kit. Four-wheel-drive, 345bhp, 0-60 in 4.7 seconds, and a top speed of 165mph make it not just one of the fastest hatchbacks, but one of the fastest everyday cars on sale today.

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Gallery: 2016 Ford Focus RS: First Drive