Ford Focus ST Mk3 Diesel Maintenance Guide
Ford Focus ST Diesel Mk3.5 Maintenance Guide
The Ford Focus ST Diesel Mk3.5, produced from 2015 to 2018, combines performance with efficiency, making it an attractive choice for those who want a sporty car with lower running costs. To keep your Focus ST Diesel Mk3.5 running smoothly and performing at its best, regular maintenance is essential. In this guide, we’ll take a look at the key maintenance tasks, recommended service intervals, and what to keep an eye out for.
Check out our full range of ST Mk3 Diesel service parts and packages here
1. Engine Oil and Oil Filter
Regular oil changes are crucial to keep the engine running smoothly. The 2.0-litre EcoBlue engine in the Focus ST Diesel Mk3.5 requires fully synthetic engine oil that meets Ford's specifications. The recommended oil change interval is every 12,500 miles (20,000 km) or 12 months, whichever comes first.
Ensure that the oil filter is replaced with each oil change to maintain good engine lubrication and avoid debris buildup, which could lead to engine damage over time.
JXL Performance recommends Genuine Ford Castrol Magnatec 0w30 Oil and the Genuine Ford Oil Filter for Ford Focus ST Mk3 Diesel
2. Air Filter
The air filter plays a vital role in ensuring the engine gets clean air, which is essential for optimal combustion and performance. Ford recommends replacing the air filter every 18,000 miles (30,000 km), although this may vary based on driving conditions. If you often drive in dusty or polluted areas, it’s worth inspecting the air filter more frequently.
Please note - a lot of owners have experienced issues with aftermarket air filters on the Diesel ST - we only recommend fitting the Genuine OEM Air Filter
3. Fuel Filter
The fuel filter prevents dirt and contaminants from entering the fuel system and causing damage to the injectors or fuel pump. Ford recommends replacing the fuel filter every 18,000 miles (30,000 km) or 24 months, whichever comes first. Regularly replacing the fuel filter helps maintain fuel efficiency and prevent issues with engine performance. Check them out here.
4. Timing Belt and Water Pump
The timing belt in the Focus ST Diesel Mk3.5 is crucial for synchronising the engine’s valves and pistons. Ford recommends replacing the timing belt and the water pump every 100,000 miles (160,000 km) or 10 years, whichever comes first. Neglecting to replace the timing belt on schedule can lead to serious engine damage if it fails, so be sure to follow this recommendation closely.
5. Brake Pads and Discs
As a performance-focused vehicle, the Focus ST Diesel Mk3.5 requires regular checks of the braking system to ensure safety and optimal performance. Brake pads should be checked regularly for wear, especially if you drive aggressively or on hilly terrain. Ford suggests checking the brake pads every 12,500 miles (20,000 km) or 12 months, and replacing them when the thickness reaches the minimum level specified in the service manual.
Brake discs should be checked for wear, scoring, or warping. If you notice any vibrations or unusual noises when braking, it could indicate worn or damaged discs. Typically, brake discs last longer than pads but should be inspected at every service.
6. Tyre Checks
Tyres should be checked regularly for wear, pressure, and alignment. Under-inflated tyres can affect fuel efficiency, handling, and safety, while uneven tyre wear can indicate alignment issues or suspension problems. Ford recommends checking tyre pressure monthly and rotating the tyres every 12,500 miles (20,000 km) to ensure even wear.
The tread depth should also be monitored. The legal minimum tread depth in the UK is 1.6 mm, but for optimal grip and performance, you should replace tyres before they reach this limit.
7. Diesel Particulate Filter (DPF)
As a diesel vehicle, the Focus ST Mk3.5 is equipped with a Diesel Particulate Filter (DPF), which helps reduce harmful emissions. Over time, the DPF may become clogged, especially if the car is driven primarily for short trips or stop-start driving. To avoid DPF issues, ensure that the car is regularly driven on longer journeys to allow the filter to regenerate.
If you experience warning lights related to the DPF or notice a loss of power, it may indicate that the filter needs cleaning or replacement. Ford recommends checking the DPF during regular services, particularly if the car has been used for a lot of city driving or short trips.
8. Cooling System
The engine’s cooling system is crucial to prevent overheating and ensure reliable performance. Ford recommends replacing the coolant every 10 years (or 100,000 miles/160,000 km) for the Focus ST Diesel Mk3.5. It’s also important to regularly check the condition of the radiator hoses and clamps for any signs of wear or leaks.
During each service, check the coolant level and ensure the system is pressurised correctly. If you notice any unusual heating or temperature fluctuations, have the cooling system inspected promptly.
9. Suspension and Steering
The suspension and steering components are essential for maintaining comfort, handling, and safety. Focus ST Diesel owners should check the suspension every 12,500 miles (20,000 km) or 12 months for signs of wear, including the shock absorbers, struts, springs, and bushings. If you notice unusual noises when driving over bumps, or if the car feels unstable or pulls to one side, it could indicate suspension issues.
The steering system should also be checked for fluid levels and leaks, as low fluid levels can affect steering performance. The power steering belt should also be inspected for wear.
10. Clutch and Gearbox
For manual transmission owners, regular checks of the clutch are essential to ensure smooth operation. If you notice difficulty engaging gears, a spongy clutch pedal, or a slipping clutch, it’s important to have it checked immediately. The Focus ST Diesel Mk3.5 uses a 6-speed manual transmission, which generally requires little maintenance aside from regular fluid checks.
For automatic transmission models, Ford recommends checking the gearbox oil every 60,000 miles (100,000 km), or every 6 years, to ensure smooth shifting and prevent premature wear.
11. Common Diesel Issues: Boosting and Performance
While not a major concern for most owners, some Focus ST Diesel Mk3.5 models may experience issues with the turbocharger and boost system. Common problems include boost leaks, faulty sensors (MAP, MAF), and wastegate issues. If you notice a loss of power or poor acceleration, it’s worth having the boost system inspected.
Another common issue with diesel engines is the Exhaust Gas Recirculation (EGR) valve, which can become clogged over time. If you notice rough idling or a drop in performance, the EGR valve may need cleaning or replacement.
Conclusion
Maintaining the Ford Focus ST Diesel Mk3.5 is relatively straightforward, but as with any vehicle, it requires attention to key components to keep it running smoothly. Stick to the recommended service intervals for oil changes, brake inspections, timing belt replacements, and other critical services to ensure the longevity and performance of your car.
By keeping on top of these maintenance tasks, you'll ensure that your Focus ST Diesel Mk3.5 remains a reliable and enjoyable performance vehicle for years to come. Regular maintenance not only helps prevent costly repairs down the line but also ensures that the car continues to deliver strong performance and efficiency.