Ford Focus ST Mk2

This is the most widespread issue on the Focus ST Mk2. The factory paint coverage on the inside of the rear wheel arches was poor, leaving bare metal exposed to moisture and road salt. Rubbing between the bumper and arch accelerates the problem. Rust typically starts as paint bubbling at the rear arch lips and spreads inward. The majority of surviving cars show this to some degree, particularly pre-facelift models (2005-2007). Minor surface rust repair costs around €250-400 per side (sanding, treating, respraying). Deep rust requiring panel work runs €600-800 per arch. Ford later added plastic protection strips to reduce bumper rubbing. Preventive measures include wax injection and self-adhesive helicopter tape between arch and bumper.

The 2.5-litre engine uses a combined oil filter and crankcase breather housing with an internal rubber diaphragm. On pre-facelift models especially, this diaphragm degrades and splits over time. Symptoms include a distinctive whistling noise at idle that disappears when you pull the dipstick out. If ignored, excessive crankcase pressure can blow out camshaft seals, and oil contaminating the timing belt can lead to catastrophic engine failure. The diaphragm cannot be purchased separately, so the entire oil filter housing must be replaced. Part cost is approximately €180-250 from Ford, plus 2-3 hours labor. Total repair typically runs €300-500. The facelift models received an improved unit. This should be checked as a priority on any pre-facelift car.

The 2.5-litre Volvo-derived engine uses wet cylinder liners with relatively thin walls between cylinders. Under extreme thermal cycling, these can develop hairline cracks. Symptoms include white smoke at idle, misfires, coolant loss, and difficulty starting. While heavily discussed online, this failure is actually rare on standard, unmodified cars. It primarily affects tuned vehicles running higher boost pressures. When it does occur, repair involves a full engine rebuild with uprated liners (€2,500-4,000) or a replacement engine (€2,000-3,000 for a used unit plus labor). A preventive block mod (shims between liners) costs approximately €500-700 including labor and timing belt change. The 2008+ facelift cars appear slightly less prone due to production refinements.

The ST uses oil-filled front lower wishbone bushes that wear out faster than standard Focus items due to the extra weight and power. Symptoms include clonking over bumps and imprecise steering feel, typically developing after 80,000-120,000 km. Because the bushes are integrated into the wishbone assembly, Ford's solution is to replace the entire wishbone at approximately €250-350 per side including labor. Aftermarket polyurethane or solid bushes (Hardrace, Powerflex) can be pressed into the existing wishbone for €150-250 total for both sides with fitting, and last longer than the originals. This is one of the most common MOT advisory items on high-mileage STs.

The alternator is positioned close to the exhaust manifold with catalytic converter, exposing it to extreme heat. This causes premature failure, especially on pre-facelift cars (2005-2007) where the heat shielding was less effective. Failure is often sudden, with the battery warning light illuminating and the car losing electrical power. A replacement alternator costs €150-250 for the part (OEM Ford with exchange), with 1.5-2 hours of labor. Total cost at an independent specialist runs €300-450, while Ford dealers charge €450-600. Most early STs that had this issue will have had it addressed by now, but it can recur on a replacement unit over time.

Three sensors work together to manage turbo boost: the MAF (Mass Air Flow) sensor, MAP (Manifold Absolute Pressure) sensor, and the Pierburg boost control solenoid behind the turbo. Over time, these degrade and cause symptoms including hesitation under load, erratic boost, lumpy idle, and ESP warning lights. Replacing all three preventatively (known as a sensor refresh) costs approximately €200-300 for parts, with straightforward labor of 1-2 hours. This is particularly recommended for cars over 100,000 km that feel sluggish or inconsistent. Individual component replacement runs €80-150 each including fitting.

The Focus ST puts considerable load through its front driveshafts. CV boot splits are common, and once the boot fails, the joint runs dry and wears rapidly. Symptoms include clicking or clunking sounds when turning, particularly on full lock. Replacement of both driveshafts using Ford remanufactured units costs approximately €350-500 including labor. Genuine Ford recon shafts are recommended over aftermarket alternatives, as budget items have poor longevity. Uprated Collins driveshafts cost approximately €800 per pair for cars running extra power, but are unnecessary on standard vehicles. Cars that have been lowered experience accelerated driveshaft wear due to increased joint angles.

A common issue across the Focus Mk2 platform, water ingress into the boot area occurs due to cracks in the paint around the boot hinge area and deteriorating body seals. In some cases, water also enters the rear footwell through blocked drainage tubes under the scuff panels. Left unaddressed, this causes corrosion of the boot floor, electrical issues with the rear lights, and musty smells. Diagnosis and repair is usually straightforward: sealing cracked areas and replacing deteriorated seals costs €100-200. If corrosion has already set in, repair costs increase to €200-400.