mechanics.trade
Radiators and cooling system
The cooling system keeps the engine at its working temperature: a pump circulates coolant, a thermostat decides when it goes through the radiator, and a fan pulls air across when the car is not moving.
What cooling system means
A leak or a stuck thermostat can overheat an engine quickly, which is why the temperature gauge is worth watching.
What the job covers
- Radiator and expansion tank replacement
- Water pump and thermostat
- Coolant leak tracing and pressure testing
- Cooling fan and sensor faults
- Coolant flush and refill
When you might need it
- The temperature gauge reading higher than usual, or the warning light coming on.
- Coolant needing topping up, or a sweet smell and coloured residue under the car.
- The heater blowing cold at idle, which often means low coolant or a failed thermostat.
What it costs, and what changes the price
Typically £200 to £700.
- Which part has failed. A thermostat is a small job; a radiator or a pump behind the timing cover is not.
- If the pump is driven by the cambelt, the belt is usually replaced at the same time.
- A pressure test to find the leak is usually charged, and is worth it rather than guessing.
How long it takes
A thermostat or hose is an hour or two. A radiator is half a day. A pump behind a timing cover is longer.
Common questions
Can I just top it up with water?
In an emergency, to get home. Coolant is antifreeze and corrosion inhibitor as well, and water alone will freeze and will corrode the engine internals.
Why does it only overheat in traffic?
At speed there is air through the radiator anyway. If it only gets hot when stationary, the cooling fan is the first suspect.
How urgent is overheating?
Very. An engine run hot can warp the head or worse within minutes. Stop, let it cool, and get it looked at rather than pressing on.