Bright green fluid with a sweet, almost syrupy smell is conventional ethylene glycol coolant (old GM, Ford, Chrysler spec). It is slick to the touch and dries to a chalky residue. The drip location tells you the source: front-center is radiator, driver-side mid-engine is water pump, under the dash is heater core. Here are the ranked causes.
The plastic side tanks on aluminum radiators crack at the seams after 7-10 years. Drips appear front-center of the car. Look for crusty green crystals on the radiator tank.
Hoses swell and crack near the clamps. The lower hose often leaks from the inside out where you cannot see it until it bursts. Squeeze hoses cold - should be firm, not crunchy or mushy.
Water pumps have a small weep hole that drips when the internal seal fails. Located on the side or back of the pump, mid-engine. Squeak or whine often accompanies the leak.
Coolant pools on the front passenger floor, windows fog with a sweet film, and the cabin smells syrupy. Outside leak is rare - usually shows up inside.
Plastic or aluminum housings warp and the gasket leaks. Sits on top of the engine where the upper rad hose connects. Small drip onto the engine block.
Plastic reservoirs crack at the seams or fittings after years of heat cycles. Drips appear directly under the tank.
Known weak point on GM V6s of the 2000s. Coolant leaks externally onto the front of the engine or internally into the intake.
| Likely Cause | Typical Cost | DIY Difficulty | Severity | Likelihood |
|---|---|---|---|---|
| Radiator Leak (Plastic Tank or Core) | $250-$700 | Moderate | High | 50% |
| Upper or Lower Radiator Hose | $30-$150 | Easy | High | 45% |
| Water Pump Weep Hole Leak | $300-$900 | Hard | High | 40% |
| Heater Core Leak (Inside Cabin) | $500-$1,500 | Pro Only | Medium | 30% |
| Thermostat Housing Gasket | $80-$300 | Moderate | Medium | 25% |
| Overflow / Expansion Tank Cracked | $50-$200 | Easy | Low | 20% |
| Intake Manifold Gasket (GM 3.1/3.4/3.8) | $400-$1,000 | Hard | High | 15% |
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Short trips around town, yes - but you should still fix it within a week. The leak will grow, and one missed top-off plus stop-and-go traffic equals overheating.
Ethylene glycol tastes sweet and is highly toxic to dogs, cats, and wildlife. Even a tablespoon can be fatal. Always clean up coolant spills with cat litter or rags - never hose it into the street.
Yes - the leak points and causes are identical. Newer cars use OAT (orange/red) or HOAT (yellow/pink) coolant but the same hoses, radiators, water pumps, and gaskets fail.
Cold pressure test the system to 15 psi with a hand pump and look for a drip or a slow gauge drop. UV dye in the coolant + a UV light at night reveals tiny leaks you cannot see in daylight.
No. The corrosion inhibitor packages react and form sludge that clogs the radiator. Drain and refill with the correct color, or use a universal coolant rated for both.
Hose or cap: $25-$150. Water pump or thermostat housing: $300-$900. Radiator: $400-$800. Heater core (labor-heavy): $800-$1,500.
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