Cooling system problems, fix before too much damage is done.

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Model: C3 2002-2005, Original shape model
Year: 2002 (02)
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This help list was circulated in the trade and I have added to it to help the C3 owner get to the bottom of their coolant loss problems.

Typically, leaks can occur in any part of the cooling system, but if there is no visible evidence of the leak, then a pressure test should be carried out. The system can be pressure tested with this kit (click) which contains a pump and the adaptors. The advantage is that the system can be tested cold, which is much safer than trying to test it hot.

Pressure test the Citroen C3 cooling system
Pressure test the Citroen C3 cooling system

Always use the correct grade/mixture of coolant. The wrong coolant can result in internal corrosion or engine overheating. Best practice is to perform a full coolant flush and refill, especially if replacing a major cooling system component, such as a water pump.
The correct coolant grade and quantity can be found in this topic (click here).

Citroen C3 coolant
Citroen C3 coolant

Any air trapped in the system will restrict the flow of coolant. Always follow the recommended procedure for bleeding air after any work has been done on the system or if an air lock is suspected. The procedure for refilling the cooling system to avoid air locks can be found in this topic, after scrolling down the page (click here)

If the thermostat becomes stuck in the closed position the coolant cannot circulate around the system and the engine will over-heat very quickly. The end result could be significant engine damage. Find the correct thermostat from this list on euro car parts after entering your registration number or model and fuel details because there are several different types of thermostat fitted to the C3.

Citroen C3 Thermostat stuck shut causes overheating engine
Citroen C3 Thermostat stuck shut causes overheating engine

Any sediment, dirt, corrosion or other contaminants in the system can block or impede the flow of coolant. Therefore whenever a major component is replaced the coolant should be flushed and replaced at the same time. This isn't often a problem with a properly maintained C3 because the original coolant is very long life, but if work had been done and the incorrect coolant used there could be corrosion or sediment. Draining, flushing and refilling with the correct grade of coolant can help.

A blocked, damaged or leaking radiator will mean that the cooling system loses efficiency and can easily lead to increased engine temperature and overheating. Pressure testing (above) can help identify leaks in the radiator and blockages are uncommon for the same reasons that blocked coolant passageways are uncommon. If your radiator leaks, find a replacement from these choices on euro car parts after entering your registration number or vehicle details for the correct fitment.

A cracked or split hose will result in loss of engine coolant. This will show up in the pressure test and is a case of replacing the faulty hose. Consider draining and refilling with fresh coolant.


The fan increases air flow over the radiator to ensure the cooling system functions correctly, particularly when travelling at low speeds or stationary. If the fan is not functioning then the vehicle is likely to suffer from overheating under these conditions. The fan is ECU controlled and there are several different fans fitted to the C3. If the fault is due to the fan (use lexia to test the fan and ECU, replace the fan on a like-for-like basis. Use this list of fans for the C3 after entering your reg or vehicle details.

The temperature sensor can give false information to the ECU which can then incorrectly control the fan and other features of the engine. Due to their low cost, it may be worth changing these sensors if you suspect a sensor fault on the C3. A number of different engine temperature sensors were fitted to different engines in the C3, use the registration number tool to find the right one(s) from these listed here (click).

If the drive belt is loose or broken, the pump will not be operating at the correct speed. This could result in a reduced coolant flow which, potentially, could lead to the vehicle over-heating. This is not at all common on the C3 because the timing belt runs the coolant pump. If you have a timing belt issue, the cooling is not going to be your biggest problem. The best advice is to change the coolant pump at the same time the cam belt is changed. Find the correct coolant pump for your C3 model from this list (click here)

water pump on a Citroen C3
water pump on a Citroen C3

You can find all the parts you need to maintain your C3 cooling system by visiting the Euro Car Parts site (click here) for car parts.
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