Question 1

When a radiator needs replacing

Accepted Answer

A radiator is an aluminium-and-plastic assembly between the engine and the grille that transfers coolant heat to the surrounding air. Leaks most commonly start at the seam between the plastic top tank and the aluminium core, because differing thermal expansion fatigues the seam over the years. An older car at 10 years old may leak as a slow weep that dries during driving and doesn't show immediately — the only sign is a gradual drop in coolant level in the expansion tank.

The leak leads to coolant loss and rising engine temperatures, especially under heavy load (motorway, inclines). The aftermath of overheating is a blown head gasket or a warped cylinder head, both thousand-euro repairs. That's why even the smallest leak should be fixed immediately. Cracked plastic top tanks and corroded radiator cores both mean the radiator has reached the end of its useful life.

Question 2

How a radiator is replaced

Accepted Answer

Coolant is drained through the lower hose and retained for reuse if it's still good. Upper and lower hoses are disconnected, electric fan and sensor connectors are unplugged and the radiator mounting bolts are undone. On many modern cars the air-conditioning condenser sits in front of the radiator — it's released from its clips and moved aside without breaking into the refrigerant circuit.

The new radiator is fitted, rubber mounts and clips are checked and the electric fan wiring is reconnected. Hoses are inspected for softening and cracks and renewed as required. The system is filled with the coolant recommended by the manufacturer (usually G12+, G13 or OAT). The airlock is removed by running the engine at idle with the heater at maximum until coolant circulates the whole system. Finally the system pressure is tested with a hand pump to confirm there are no leaks.

Question 3

Why do radiators start leaking?

Accepted Answer

Radiator leaks are almost always age-related. Plastic tanks stiffen from UV and heat cycling and start cracking, particularly at the base of pipe connections. The aluminium core can also begin corroding from the inside if coolant hasn't been changed often enough and its corrosion-inhibition additives are depleted. Small external impacts — a flying stone, a minor rear-end — can cause cracks that don't show up straight away. Driving cold without a thermostat or with the wrong coolant-water mix creates a freezing risk that can split the entire core internally. A regular coolant change every 4 years plus hose inspection at servicing are the best way to prevent leaks.

Radiator Replacement in Vantaa