Engines · Ford
Ford 2.5T five-cylinder (Focus ST and RS Mk2) common problems
The 2.5T is a 2.5 litre turbocharged five-cylinder petrol engine derived from Volvo's T5 unit, fitted to the Focus ST from 2005 with 225hp and to the Focus RS from 2009 with 300bhp. Specialists rate it as tough in standard form, and its known faults are well understood.
Common problems and what to look for on the 2.5T five-cylinder
The known issues most worth checking when you view a car with this engine. None of them means a car is a bad buy, but they're worth knowing about before you buy, and a good history often shows they've been dealt with.
A whistle at idle from the oil filter housing
What to look for: With the bonnet open and the engine idling, listen for a whistle. Pull the dipstick out slightly: if the noise stops, note it. Look around the oil filter housing at the front of the engine for wet oil.
Why it matters: The oil filter housing contains a breather diaphragm that can split, which causes the whistle at idle. Ford is understood to have addressed it in 2008, and the fix is a replacement housing.
Cylinder liners on early STs
What to look for: With the engine cold, remove the oil filler cap and look underneath for a creamy, mayonnaise-like residue. On start-up and on the drive, watch for white smoke from the exhaust and feel for a misfire, especially from cold.
Why it matters: Some early Focus ST engines suffered split cylinder liners, which let coolant and oil mix. It affects relatively few cars. The repair shims the liners and is usually done with the cambelt and water pump, and Ford is understood to have revised the blocks on post-2008 facelift cars.
Cambelt and camshaft oil seals
What to look for: Check the history for the date and mileage of the last cambelt change, and whether the tensioner and seals were done with it. With a torch, look around the cambelt cover at the front of the engine for oil.
Why it matters: Ford's official interval is ten years or 125,000 miles, whichever comes first, and many specialists suggest changing it sooner. Camshaft oil seal leaks are quite common, and oil reaching the belt weakens it, often hidden behind the covers. Seals, belt and tensioner are usually done together, and a car with that invoice is in a good position.
More known issues, covered in the full guide for each car
- Boost problems
- RS: the plastic intake plenum
- Radiator and coolant leaks
Cars with the 2.5T five-cylinder
- Ford Focus Mk2: Focus ST, 2005 to 2010
- Ford Focus RS Mk2: Focus RS and RS500, 2009 to 2010
A pre-purchase inspection guide for your car
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General points for the engine, last checked October 2026. Every car is different, so treat this as a guide to what to look at, not a verdict on any car. CrankSight is independent and has no connection with any manufacturer.