Car Overheating: Why It Happens and What to Do Right Now

Driveway Pinpoint Test

With the engine cold, remove the radiator cap (NEVER when hot — serious burn risk) and start the engine. Watch the coolant through the radiator neck for the first 5–10 minutes. If the coolant is perfectly still and not circulating, the thermostat is stuck closed — it should open and let coolant flow once the engine reaches operating temperature. A correctly opening thermostat causes visible flow in the radiator after a few minutes of running.

Driveway Pinpoint Test

With the engine at operating temperature (but NOT at the overheating point), open the hood and look for coolant leaking from around the water pump pulley area or a small weep hole underneath the pump. You may also hear a high-pitched whine or grinding from the front of the engine. Shake the water pump pulley gently when cold — any wobble means the bearing is failing.

Driveway Pinpoint Test

With the engine cold, inspect the front of the radiator (the fin-covered grid behind the front bumper). Bent fins reduce airflow. Look for dried coolant (green, orange, or pink crust) around any seams or the plastic end tanks — that indicates a leak. Check the coolant overflow reservoir: consistently low level means coolant is escaping somewhere.

Driveway Pinpoint Test

With the engine cold, squeeze the large rubber hoses connecting the radiator to the engine (upper and lower radiator hoses). A healthy hose feels firm but pliable. A hose that collapses flat easily, feels brittle and cracked, or is swollen and mushy needs replacement. Look for coolant stains (white or rust-colored residue) at the hose clamp connections.