Low coolant should never simply be topped off and forgotten. A cooling system that loses coolant will eventually overheat, and overheating is one of the most common causes of warped heads and failed head gaskets. Finding the leak early protects the rest of the engine.
Signs of a Coolant Leak
- Coolant level dropping in the reservoir.
- Puddles of green, orange, pink or blue fluid under the vehicle.
- A sweet smell, or steam from the engine bay.
- White, green or pink crusty residue on hoses, fittings or the engine.
- Temperature gauge rising, or heater output dropping.
Common External Leak Sources
- Hoses and clamps: cracked, soft or swollen hoses and loose clamps.
- Radiator: leaks at seams, tanks or from core damage.
- Water pump: coolant at the weep hole is a sign the pump seal is failing; leaks can also come from the pump gasket.
- Thermostat housing gasket.
- Intake manifold gasket on engines with coolant passages in the manifold.
- Expansion (freeze) plugs in the block and heads.
- Heater core and hoses: damp passenger floor or fogged windows.
Internal Leak Sources
When coolant disappears with no external sign, look for internal leaks:
- Head gasket failure or a cracked head or block.
- Intake manifold gasket leaking into the lifter valley.
- Oil cooler failure on engines that use a coolant-to-oil cooler.
How to Find the Leak
- With the engine cool, pressure-test the cooling system to the cap rating and watch for drips or pressure loss.
- Pressure-test the radiator cap too — a weak cap can cause coolant loss and overheating.
- Add a UV dye to the coolant and inspect with a UV light after running the engine.
- If no external leak is found, perform a combustion leak test and check the oil for coolant.
Repair Tips
Replace failed gaskets and components with the correct parts, use the coolant type specified by the vehicle manufacturer and bleed air from the system completely after the repair.
Evergreen Cooling and Sealing Parts
Evergreen offers water pumps, timing kits with water pumps, and cooling system and engine gaskets identified by application. Use the Evergreen eCatalog to find the right parts. Browse Evergreen cooling system parts.
