The reasons behind a car temperature gauge reading high may include: Low coolant in the system. Incorrect coolant for the application. Cooling system problem. Bad temperature gauge. Some vehicle models use a warning light instead of a gauge. Whether the gauge reads high or the light comes on, it means engine driving conditions are not safe Make sure the engine is at a cool or lukewarm temperature before adding the coolant. 2. Open the Hood and Locate the Engine Coolant Tank. Your tank will have a fill range marked on the side. Once the engine is cold, the coolant level should reach up to the “cold fill” mark. 3. Loosen the Reservoir Cap. To ensure this, you must check and add coolant periodically in order to maintain an adequate radiator fluid level. Part 1 of 2: Check the radiator fluid. Materials Needed. Gloves; Towel or rag; Step 1: Make sure the engine is cool. Before checking the radiator fluid, the car should be turned off and allowed to sit until the radiator is cool to Also check out:Checking your tyre pressure and tread wear: Importance of checking your coolant level. Coolant circulates through the engine, taking the heat and transferring it to the air via a radiator. While coolant repeats the process through your cooling system, your coolant can evaporate and, its level can get lower and lower over time. Leaking coolant: A leak in the cooling system can cause the coolant level to drop too low. Check for leaks around the radiator hoses, water pump, and engine block. Overheated engine: An overheated engine can cause the coolant to boil and evaporate. This will cause the coolant level to drop and trigger the warning light. Locate the coolant reservoir (tank) in the engine bay. You can check the engine coolant level simply by looking at the side of the tank. If the level is below the minimum mark, you must add coolant, or your vehicle may overheat. Do not open the cap when the engine is hot. Turn the ignition on, but don’t start the engine and check the engine 4 days ago · Step 3: Locate the Coolant Reservoir Most modern vehicles have a translucent plastic coolant reservoir. It is typically located near the radiator and is marked with "Max" and "Min" lines to indicate the acceptable coolant level range. Step 4: Inspect the Coolant Reservoir TpjSRM2.