The company told Autocar that the problem, which appears to be affecting cars of as little as 6000 miles, is causing some 2016 and 2017 models to produce “white exhaust smoke” as they burn coolant during cold running.
When asked whether the issue will result in a recall, a spokesman said Ford is "working on a repair for all customers", suggesting a fix could be rolled out even to include cars not currently affected.
“In the meantime, if vehicles show these symptoms, customers should visit their dealer for an inspection and repair under warranty,” the spokesman added.
Ford has already replaced several affected engines with all-new units built to the latest specification under warranty.
No official line as to the cause of the problem has been released, but a large number of posts on internet forums from Mk3 Focus RS owners have suggested that the head gasket is failing to seal the engine block to the head effectively.
However, rather than being a design issue of the head gasket itself, the problem has been linked to block distortion. It is believed that the physical shape of the engine changes through multiple heat cycles, eventually preventing the gasket from sealing the two parts correctly.
This, owners have suggested, is allowing coolant to leak into the cylinders when the engine is cold, causing issues such as a smoking exhaust and misfire before the engine is up to its optimum temperature.
A Focus RS owner, YouTube user MarkCup70, claims in a video that he has come across a dealership report stating that another car with the aforementioned symptoms was “losing coolant” due to the cylinder block being “out of tolerance”. The report concluded that the car now had a “distorted cylinder head”.
The problem is not thought to affect Mustangs with the same engine due to the use of a different alloy for its block and head. The Focus RS’s engine is made from an upgraded alloy with a cast-iron lining and gets its own head gasket design – requirements for the car’s higher 345bhp output.