MinorAffected: 2008-201260,000–120,000 miles

Ford Fiesta Mk6 1.25 82bhp — Engine Thermostat Sticking Open

The engine coolant thermostat fails in the 'open' position. The engine never reaches its optimal operating temperature, killing fuel economy.

Severity

Minor

DIY Difficulty

Moderate

Est. Cost

£100–£250

OBD Codes

P0128

Component Diagram

Cooling

Typical layout and location for the Cooling assembly.

Reference Illustration

Symptoms

Temperature gauge drops when driving on the motorway
Heater blows lukewarm air in winter
MPG drops significantly
Engine takes a very long time to warm up

Root Cause

The wax element inside the thermostat degrades, or the return spring weakens, preventing the valve from closing off coolant flow to the radiator.

How To Fix

Scan for P0128 (Coolant Thermostat - Coolant Temp Below Regulating Temp).
Replace the thermostat housing unit and gasket.
Bleed the cooling system of air.
Cost: £100-250

Estimated Repair Costs

Repair Option	Est. Cost (GBP)
DIY (parts only)	£40–£100
Independent Garage	£100–£250
Main Dealership	£160–£400

Other Faults on This Variant

Front Wheel Bearing Failure

Moderate

2008-201260,000–100,000 miles£120–£250

Front wheel bearing wear is extremely common on the Mk6 Fiesta. Most examples will need at least one bearing replaced between 60,000 and 100,000 miles.

Power Steering Pump Failure

Moderate

2008-201270,000–130,000 miles£180–£380

The hydraulic power steering pump on the Mk6 Fiesta fails with age and mileage, making the steering very heavy — especially at low speeds and when parking.

Ignition Coil Pack Failure

Moderate

2002-200840,000–90,000 miles£80–£120

The single coil pack block fails, causing a 2-cylinder misfire.

Disclaimer: Repair cost estimates are indicative and based on community data. Always get a quote from a qualified mechanic before proceeding with any repair.