Coolant leak from the radiator

Symptoms

• Coolant puddle specifically at the very front of the car, under the radiator
• Visible crusty white or colored residue on the radiator itself
• Coolant level drops steadily
• Sometimes a hissing sound when the engine is warm and under pressure

Likely causes

• CommonCorrosion causing a small pinhole leak in the radiator coreEspecially in older aluminum-core radiators, internal corrosion can eat through thin metal over years.
• CommonCracked plastic end tankMost modern radiators have plastic tanks on an aluminum core; the plastic becomes brittle with heat cycling and can crack, especially near the seams.
• PossibleDamage from a rock or road debris impactThe radiator sits behind the grille and can be punctured by debris kicked up while driving.
• PossibleFailed radiator cap not maintaining proper system pressureCan cause coolant to escape through the overflow more than usual, sometimes mistaken for a radiator leak itself.

What to do

1. Inspect the radiator visually for cracks, especially around the plastic end tank seams, and check for crusty coolant residue marking a slow leak.
2. Check the radiator cap's seal for wear or damage, and consider replacing it since it's inexpensive and can cause similar symptoms.
3. Have a pressure test performed at a shop if the leak point isn't obvious, since this can reveal a small leak that's hard to see with the engine off.
4. Avoid using a stop-leak additive as a long-term fix, since it can clog other parts of the cooling system, though it may buy time in an emergency.
5. Replace the radiator if a crack or corrosion leak is confirmed, since radiators generally aren't repairable long-term once compromised.

Tools and parts

• Flashlight

When to call a pro

See a mechanic if you're not comfortable draining and refilling the cooling system properly, since air pockets left after a repair can cause overheating or poor heater performance.

Safety