MinorAffected: 2004-201160,000–120,000 miles

Ford Focus Mk2 1.8 TDCi — 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

Electric Window Regulator Cable Failure

Minor

2004-201150,000–120,000 miles£100–£200

The cables inside the electric window regulator mechanism fray and snap, causing the window glass to drop into the door frame.

Starter Motor Solenoid / Brush Wear

Severe

2004-201170,000–130,000 miles£150–£350

The starter motor wears out internally. This is particularly common on vehicles equipped with Stop/Start systems.

Dual Mass Flywheel (DMF) Failure

Severe

2004-201170,000–120,000 miles£600–£800

The 1.8 TDCi produces strong low-end torque which destroys the internal springs of the Dual Mass Flywheel.

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