Car-maker admits 2.3-litre turbo four can suffer coolant loss and misfire problem when cold, fix said to be on the way

Ford UK has been forced to admit early versions of its Focus RS can develop an engine issue that sees it misfire, lose coolant and emit white smoke when running during its warm-up cycle.

The issue, thought to affect some 2016 and 2017 models, was unearthed by British magazine Autocar after some owners took to Focus RS forums and YouTube to vent their frustration with an engine fault many Ford dealers are struggling to fix.

In the worst cases, some users reported that their faulty engines couldn’t be fixed and were replaced by new engines.

Ford UK has yet to reveal the actual problem, but it’s thought to be related to the head gasket failing.

Some owners have linked the issue to block distortion that occurs following a full heat cycle that sees the block and head separate when cooling down, allowing the coolant to leak into the cylinders when cold.

Adding credibility to this theory is YouTuber MarkCup70’s claim he has seen an engineering report that diagnosed a Focus RS as suffering a head gasket sealing problem because a cylinder-head was “out of tolerance” with the block.

Ford has yet to issue a recall but told Autocar it was “working on a repair for all its customers”.

It also added that if any Focus RS vehicles develop these symptoms customers should “visit their dealer for an inspection and repair under warranty”.

According to owners, the same problem is not thought to affect the Mustang fitted with the turbocharged 2.3-litre four-cylinder engine because it uses a different alloy material for the block and head.

The Focus RS, meanwhile, blends an upgraded alloy with a cast-iron lining to help engineers extract the standard car’s 257kW.