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Autopapyrus · Citroën C4 (2nd generation) 1.6 VTi 120 (2013)
https://autopapyrus.com/guides/citroen/c4/cooling-system-diagnosis/
Compiled automatically from service literature and owner experience. Specs are for the typical configuration — check them against your exact car before you start.

Citroën C4 (2nd generation) 1.6 VTi 120 (2013): Cooling System Diagnosis

On the EP6 engine (1.6 VTi, 120 hp), typical cooling problems are: coolant loss through hairline cracks in the hoses and thermostat housing, a stuck or failed thermostat, a worn water pump, and a faulty fan or temperature sensor. Diagnosis goes from simple to complex: inspection, checking coolant level and condition, pressure test, then temperature tests and reading scanner data.

Difficulty: Medium Time: 1-2 hours Steps: 13 Tools: flashlight, manual cooling system pressure tester with adapters, infrared thermometer, hydrometer or refractometer for coolant, OBD-II scanner with live data, gloves, drain pan

Part

  • 🔩 The diagnosis itself does not require any parts. Common replacement candidates: thermostat assembly with housing (on this engine it is electronically controlled with a heater), water pump, radiator, expansion tank cap, coolant hoses, coolant temperature sensor, electric cooling fan. Confirm exact prices with your parts supplier
There's a full repair manual for this car Every system, wiring diagrams and torque specs — not just this job. Haynes and 4 more. See manuals →

Step by step

13 steps
  1. Do the check on a COLD engine. Park the car on a level surface and check the coolant level in the expansion tank against the min/max marks. Do not open the cap on a hot engine: pressurized coolant causes burns.
  2. Inspect the condition of the coolant. A rusty or cloudy color, an oil film, or foam indicates old coolant, corrosion, or oil or combustion gases getting into the system. If you see oil traces on the coolant surface or on the cap, suspect the head gasket or the oil cooler. Also check for emulsion under the oil filler cap.
  3. Visually inspect the system with a flashlight: the radiator and heater hoses, the thermostat housing, pipe connections, the radiator (signs of seepage, white or colored streaks), the area around the water pump, and the ground under the car. Look for cracks and seepage on plastic parts, which often fail from age and heat.
  4. Check the expansion tank cap: the condition of the seal, spring, and valve. A weak cap does not hold pressure and causes boiling over and coolant loss. The nominal opening pressure is marked on the cap itself. If in doubt, simply replace it with a new one.
  5. Pressure test the system with a manual tester on a cold engine. Pump the pressure up to the value marked on the cap (usually around 1.2-1.5 bar). The pressure should hold for at least 10-15 minutes without dropping. If it drops, look for the leak by drips, hissing, and residue. A drop with no visible leaks may indicate an internal leak (cylinder head, head gasket).
  6. Connect the scanner and read the engine fault codes. Typical codes for cooling problems: coolant temperature sensor deviations, thermostat control faults, a lean mixture fault (P0171), and a thermostat control circuit fault (P0597). With a faulty electronic thermostat, the control unit may limit power and enter limp mode. This is accompanied by the Check Engine light and sometimes by the A/C being switched off.
  7. Warm the engine up at idle and watch the coolant temperature on the scanner. Operating temperature is about 90-105 °C. If the engine warms up too slowly or does not reach normal temperature, suspect a thermostat stuck open or a faulty sensor. If it overheats quickly, suspect a thermostat stuck closed, the water pump, the radiator, or the fan.
  8. Check thermostat operation by touch or with an infrared thermometer. After starting a cold engine, the lower radiator hose should stay cold until the temperature approaches operating level. Then the hose should heat up sharply. If the lower hose warms up right along with the engine, the thermostat is leaking or open. If the upper hose is hot while the lower hose stays cold even at high temperature, the thermostat is stuck closed. Be careful around moving parts.
  9. Check that the electric fan switches on. When the temperature reaches the threshold or when the A/C is turned on, the fan should start. If it does not, check the fuse, relay, connector, and the fan itself (if needed, force it on with the scanner in actuator test mode).
  10. Check the water pump. Signs of wear: pulley play, bearing noise, coolant traces on the housing or at the weep hole, and poor circulation during overheating. A noticeable temperature difference between the upper and lower radiator hoses on a warmed-up engine is a sign of poor circulation.
  11. Check the radiator and heater: whether the cabin warms up well, whether there is an air pocket, and whether the radiator fins are clogged on the outside (leaves, dirt between the A/C condenser and the cooling radiator). A cold heater with a hot engine means air in the system or a blockage.
  12. Check the coolant density with a refractometer or hydrometer. This shows its freezing point and remaining service life. If the coolant is old, replace it according to the service schedule and use the type specified by the vehicle manufacturer.
  13. After any work on the cooling circuit, bleed the air using the procedure for this model (top up to the proper level, warm up with the filler open or the bleed screw open, and check the level after the engine cools). Air pockets on this engine cause local overheating and false readings.

Common mistakes and warnings

  • Do not open the expansion tank cap on a hot engine: severe burns are possible. Do not drive while the engine is overheating: it quickly leads to a warped cylinder head and a blown head gasket. Tightening torques for the hose clamps, thermostat housing bolts, and water pump, as well as the exact cooling system capacity for this engine, are not clearly confirmed in open sources, so check them against the manufacturer's service manual. If you suspect the head gasket after diagnosis, or you have no experience working with a pressurized system, go to a repair shop.
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