In Spain, professional auto mechanic Juan JosΓ© has drawn drivers’ attention to one of the most common mistakes in car maintenance. According to him, trying to open the coolant reservoir cap when the engine hasn’t cooled down yet can have serious consequences for both health and the vehicle itself.
The expert noted that many drivers, noticing a suspicious fluid level or wanting to check its condition, rush to open the reservoir right after stopping the car. However, this is exactly when the system still has high temperature and pressure, making the operation extremely dangerous.
Unlike other automotive fluids, such as oil or brake fluid, coolant is under pressure when the engine is running or has just been turned off. Opening the cap in these conditions causes a sudden release of steam and hot liquid, which can result in severe burns to the face and hands.
The mechanic explained that a carβs cooling system is designed to withstand temperatures above 100 degrees due to its sealed construction. The cap acts as a valve, releasing excess pressure only under certain conditions. If opened prematurely, the fluid instantly boils and bursts out under pressure.
Besides the risk of injury, such actions can also damage your car. If you open the cap abruptly, the coolant may pour out completely, and air can enter the system. This can cause the engine to overheat and lead to expensive repairs.
To avoid these issues, experts recommend always waiting until the engine has fully cooled down. You can check if the system has cooled by gently pressing on the hose: if it’s soft and not under pressure, you can slowly open the cap while controlling the release of air. Be especially careful with radiators where the cap opens half a turn β in these cases, the risk of coolant being ejected is even higher.
In short, a simple rule β never open the coolant reservoir when the engine is hot β will help protect your health and save you from unnecessary car repairs.
