What Does a Radiator (Pressure) Cap Do?
The humble radiator cap is more important than it looks. A Cranbourne West specialist explains.
What it is & what it does
The radiator/expansion cap seals the cooling system and holds it under pressure, which raises the coolant’s boiling point so the engine can run hotter without boiling over. It also lets coolant flow to and from the overflow as it expands.
A cheap part doing a critical job.
Signs of trouble & how we help
A failed cap causes overheating, coolant loss, or boiling/overflow — and it’s one of the cheapest cooling fixes, so it’s always checked when diagnosing overheating. A weak cap can mimic bigger problems.
We pressure-test the cap and system together so a $20 cap isn’t mistaken for a big repair.
Questions about your car? Just ask.
Understanding what’s under the bonnet makes servicing decisions easier — and we’re always happy to explain what your car needs and why, in plain English.
Book a service or a check with a Cranbourne West specialist online in 60 seconds, or call 03 8782 0711.
What Does a Radiator (Pressure) Cap Do? — FAQ
It seals and pressurises the cooling system, raising the boiling point and managing coolant flow to the overflow.
Yes — and coolant loss or boiling. It’s a cheap part we always check first.
We pressure-test the cap and system together.
No — one of the cheapest cooling fixes, which is why we rule it out early.
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