While the engine is off, your coolant reservoir should be about 30% full. The most common reason for a vehicle to overheat is a leak in the coolant reservoir or one of the attached hoses.Click to see full answer. People also ask, what level should coolant be at?The coolant level should be at the tank’s MAX or HOT line when the engine is hot, and lower when it’s cold. is it normal for coolant to get low? There are only two ways that the coolant in your car gets low. There is a leak, either in the radiator, the hoses, or the engine. The thermostat is set too high or there is a blockage, and the coolant is getting heated to boiling point, and the vapor is exiting the system, which reduces the coolant level. Keeping this in view, can you put too much coolant in your car? Most of the time, excess coolant is expelled from an overflow hose. You’ll likely see a puddle of coolant beneath your car if this has happened. In worst case scenarios, overfilling your antifreeze tank can lead to electrical damage if overflow comes into contact with engine wiring.Can I just top up my coolant?If your coolant level is too low (below or near the lower mark), top it up using a 50/50 mixture of water and antifreeze (for normal driving conditions), or pour pre-mixed antifreeze straight into the reservoir. You can use clean tap water in an emergency, but antifreeze should be added as soon as possible.