When the temp gauge climbs but the coolant tank looks full, your problem isn't a leak - it's flow. Coolant is in the system, but something is keeping it from moving heat away from the engine. Here are the four usual suspects.
The thermostat opens when coolant hits ~195°F to let it flow to the radiator. When stuck closed, hot coolant just circulates inside the engine and overheats. Often you'll see a cold radiator hose with a screaming-hot engine. Code P0128 or P0217 may appear.
Get a full diagnosis →At low speed (idling, stop-and-go), the engine relies on the electric fan to pull air through the radiator. Bad fan motor, bad relay, or bad temp sensor = no fan = overheating in traffic. Note: it cools fine at highway speed when wind does the job.
Get a full diagnosis →Plastic impellers can disintegrate or slip on the shaft. Pump pulley spins (belt looks fine) but no water moves. Diagnosis: at idle when warm, the upper radiator hose should pulse - no pulse = no flow.
Get a full diagnosis →A small head gasket leak pushes combustion gases into the cooling system, creating air pockets that cause hot spots. Symptoms: bubbles in the reservoir, white smoke from exhaust, sweet smell, or coolant disappearing without a visible leak.
Get a full diagnosis →Tell us your symptoms and any codes. In under 60 seconds you'll get a step-by-step diagnosis tailored to your car, the parts you need, and what a fair repair should cost.
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If your scanner is showing one of these, that's your starting point. Tap any code for full causes and repair costs.
No. Even a few minutes of overheating can warp the cylinder head, blow the head gasket, or crack the block. Pull over, shut off, and tow if needed. The tow is way cheaper than the engine.
Because the problem is flow, not volume. A stuck thermostat blocks coolant from reaching the radiator. A dead water pump impeller stops circulation. A failed fan stops air from pulling heat from the radiator. Coolant level looks fine because none is leaking.
Yes - a bad ECT sensor can either falsely show overheating (when engine is fine) or fail to trigger the cooling fan (so it really does overheat). Touch the upper hose with a back of hand near the engine - actual heat doesn't lie.
Thermostat: $25-80 part, 1 hour labor. Cooling fan motor: $80-300 + 1-2 hours. Water pump: $50-300 + 3-6 hours. Head gasket: $1,500-3,000. Diagnose before throwing money at parts.
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