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Low coolant and rising temp on my 2020 IS 300 – Where to check for leaks?

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Mike T. · rep 0 · May 25, 3:29 AM · 1 replies · solved · Question

Vehicle: 2020 Lexus IS 300 AWD

Hey everyone, I've got a 2020 Lexus IS 300 AWD with about 45,000 miles. Lately, I've noticed my coolant reservoir is pretty low, and the engine temperature gauge has started creeping up a bit higher than usual, especially in traffic. No obvious puddles under the car, but I can smell something sweet sometimes.

I'm worried about overheating. What are the common places for coolant leaks on these cars? Is there anything I can check myself before taking it to a shop? I haven't seen any warning lights yet, but I want to catch this early.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 3:29 AM

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  1. Visual Inspection:
    • Radiator Hoses: Check the upper and lower radiator hoses for cracks, bulges, or leaks at the clamps.
    • Radiator: Look for green/pink residue on the radiator fins, especially at the top and bottom tanks.
    • Water Pump: The water pump is a common failure point. Look for leaks or residue around its housing.
    • Thermostat Housing: Check the housing and its gasket for signs of leakage.
    • Heater Hoses/Core: Follow the hoses leading to the firewall for the heater core. A sweet smell inside the cabin strongly suggests a heater core leak.
    • Coolant Reservoir: Inspect the reservoir itself for cracks.
  2. Pressure Test (Shop Recommended): A cooling system pressure test is the most effective way to find small, elusive leaks. A technician will pressurize the system and visually inspect for drips.
  3. Common Causes:
    • Hose Degradation: Over time, rubber hoses can harden, crack, or clamps can loosen.
    • Gasket Failure: Gaskets (e.g., water pump, thermostat housing) can dry out and fail.
    • Radiator Damage: Road debris can cause small punctures in the radiator.
    • Water Pump Seal Failure: The internal seals of the water pump can wear out.
  4. When to See a Shop: If you can't easily locate the leak, or if the temperature gauge continues to rise, it's critical to stop driving and get it to a professional shop immediately. Overheating can cause severe engine damage (e.g., head gasket failure). While not directly an OBD code for a leak, persistent low coolant or overheating could trigger codes like P0117 (Engine Coolant Temperature Sensor Low Input) or P0125 (Insufficient Coolant Temperature for Closed Loop Fuel Control) if the sensor readings are out of range due to actual temperature issues.
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