Renault Clio Mk3 1.5 dCi 86bhp — 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
MinorDIY Difficulty
Moderate
Est. Cost
£100–£250
OBD Codes
P0128Cooling
Typical layout and location for the Cooling assembly.
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
Injector Return Pipe Failure
SevereThe K9K 1.5 dCi in the Clio Mk3 has a known failure on the injector fuel return pipes. The plastic fittings crack and cause a fuel leak — a fire risk that must be addressed immediately.
EDC Automated Clutch Actuator Failure
SevereThe EDC (Easy Drive) semi-automatic gearbox variant of the 1.5 dCi Clio uses an electric clutch actuator. When this fails, the car refuses to move — and replacements are expensive.
Delphi Fuel Injector Failure
CriticalEarly 1.5 dCi engines (K9K) used Delphi fuel injectors that were highly prone to failure, causing misfires and sometimes producing metal swarf that destroys the entire fuel system.
Disclaimer: Repair cost estimates are indicative and based on community data. Always get a quote from a qualified mechanic before proceeding with any repair.