Cooling
What is a Coolant Expansion Tank?
Gives hot coolant somewhere to expand into.
Simplified animation — not to scale.
In plain English
A translucent plastic tank in the engine bay connected to the cooling system, with MIN and MAX markings on the side.
A simple analogy
"It is the cooling system's overflow cup — somewhere for the hot fluid to swell into without bursting a hose."
How it works
As coolant heats up it expands and rises into the tank; as it cools it contracts back into the system. The tank also lets you check and top up the level easily.
Signs of trouble
- ⚠Cracks or splits in the tank
- ⚠Coolant level constantly dropping
- ⚠Sweet smell or visible leaks
- ⚠Tank bulging or distorted
Rough UK cost
£70–£250
Parts: £25–£120
Labour: £40–£120
Always get a written quote. Prices vary by car, region, and parts brand.
Heads up: Carautonomy is for general guidance only. If your car is showing warning lights or behaving oddly, get it looked at by a qualified mechanic.