Popular car engines and transmissions plagued by costly reliability flaws

A new report highlights persistent reliability issues in several popular car engines and transmissions. Some models from Ford, Stellantis, Mazda, and Jaguar Land Rover show significantly higher failure rates than average. Owners of affected vehicles often face repair bills running into thousands of pounds. Ford’s 1.0-litre EcoBoost petrol engines, produced between 2011 and 2018, suffer from a design flaw involving a 'wet belt' that degrades over time. When the belt breaks down, fragments mix with the engine oil, leading to catastrophic failure. The issue affects multiple models, including the Fiesta, Focus, B-Max, C-Max, EcoSport, and Mondeo. In 2018, Ford abandoned the problematic belt system in favour of a more durable chain drive.

The same manufacturer’s PowerShift automatic gearboxes, fitted to cars between 2010 and 2019, also present major problems. Drivers report jerky gear changes, sudden loss of power, and complete gearbox failure. Repair costs for these faults average over £2,350. The affected models include the Fiesta, Focus, Puma, EcoSport, Mondeo, S-Max, and Galaxy.

Stellantis’ 1.0- and 1.2-litre PureTech petrol engines, which also use a 'wet belt', have a 31% higher failure rate than the industry average. Repairs typically cost around £2,100. The company now offers UK customers compensation for excessive oil consumption or premature timing belt failure linked to these engines.

Mazda’s 2.2-litre diesel engines fail more than twice as often as the average, with repair bills reaching approximately £3,500. Meanwhile, Jaguar Land Rover’s 2.0-litre Ingenium diesel engines are 162% more likely to break down, with fixes costing over £5,000. The report also flags Continuously Variable Transmissions (CVTs) as particularly fragile, with average repair costs hitting £2,924. Owners of these vehicles face high repair costs, often exceeding £2,000 for gearbox or engine issues. Stellantis has introduced a compensation scheme for affected UK customers, but other manufacturers have yet to follow. The findings underscore the financial risks of buying certain used models without thorough mechanical checks.