Can You Add Brake Fluid While Car Is Hot?

Adding brake fluid to a car is an easy task. But can you add brake fluid while car is hot? When the engine is hot, you should not allow spillages at this stage. It is unsafe to add brake fluid to a hot car, do you need to wait for it to cool down? Additionally, you need to continue checking your car’s brake fluid level. How can you do this? We will discuss these questions and get the answers we need.

can you add brake fluid while car is hot

Can you add brake fluid while car is hot?

No, you cannot add brake fluid while your car is still hot. When a car is hot, any drops of brake fluid on the hot surfaces can have the potential to produce smoke or even start a fire. Touching any part of a hot engine can burn you. Car manufacturers always put warning signs to deter anyone from touching hot surfaces. This shows that it is unsafe to start topping up fluid while the car is hot. 

Do you have to let your car cool down before adding brake fluid?

Yes, you must allow your car to cool down before adding brake fluid. Even if you are in a hurry, safety comes first. At least you can manage to wait up to 30 minutes. This is the average time it takes for a car to cool down to a safe limit, allowing you to handle some tasks. Otherwise, for most cars, it can take up to one or two hours. After it has cooled down, you should know how to put brake fluid in car reservoir while adding the liquid. You can’t afford any trial and error. Always use better quality dot 4 brake fluid as recommended.

How to check car brake fluid?

The procedure for checking brake fluid is very simple. If you know how to add brake fluid to your car, then you already know about where to start. You first need to ensure that you park the car on level ground that will not disturb the reading. Then you can follow the steps below:

Step 1:

Open the hood only when you are sure it is safe. If you suspect your car is overheating, you must take extra care before proceeding.

Step 2:

Locate the fluid reservoir. The manufacturers have made sure that the master cylinder is easy to locate. On top of the master cylinder, you will find the reservoir for brake fluid.

Step 3:

Open the brake fluid reservoir to allow you to check the level. The container is usually transparent and may not need an opening to see the level.

check brake fluid hot or cold

Step 4:

Look out for fluid level markings. One mark indicates where the level is at its lowest. The other mark indicates where it can reach its highest or maximum.

Ensure that the level is between the two marks. If it is below, you should top it up. But if it is above the maximum limit, you may need to remove the excess.

Can you just change brake fluid without bleeding?

The answer is no. You cannot just change the brake fluid in a system without bleeding. When you decide to change brake fluid, bleeding should also be on your list of tasks. After some time, the system accumulates water which you have to remove. When you remove the old brake fluid, air will also enter the system. You have to remove this air and any other contaminants or foreign particles.

Can I mix old and new brake fluid?

Yes, it is safe to mix old and new brake fluids. This only comes with one condition. The two fluids should have the same chemical composition. It should also not be too old when you add the new one. If the old brake fluid level is very low and in bad condition, you may need to change the fluid and use the new one. As a rule of thumb, ensure that the new fluid is topping up the old one. You only need to add a small quantity. In the process, always use the correct procedure for adding brake fluid to car.

What happens if I overfill brake fluid?

Overfilling brake fluid adds excessive pressure to the system. This means that even the seals will become weak and give in. The system will result in the brake pads rubbing against the disc. The brake pads will wear out faster than usual. The rubbing action will also cause overheating in the whole system. With the same pressure in the system, the seals will also fail earlier. Deciding when to add brake fluid should come with sticking to the right quantities. Otherwise, overfilling will eventually cause the system to fail much earlier than expected. Keep the level above the minimum mark and below the maximum mark.

How long will brake fluid last?

The time taken for brake fluid level to drop varies between manufacturers. In most cases, it can range from one to three years or every 45000 miles. But this is also subject to the type of usage the car is subject to. Vehicles that are busy or cover long distances will only last for a short time as those put to moderate use. In any case, the original equipment manufacturer has the final say. You will find such details in the service manual for the car. This means that the length of time may not be the only factor worth looking at. You also need to consider the distance it is covering.

How often do you really need to change brake fluid?

You should change brake fluid as often as needed to keep your system effective and efficient. In most cases, you may change it every two years, depending on the manufacturer’s specifications. In some cases, consider replacing it after traveling at least 60,000 km. When you have decided the right time, you can even try adding the fluid if the level is too low. This leads to the question, can you add brake fluid yourself, or do you need a trained mechanic at all times? If you have the skill for the task, there is no problem. You can handle it on your own. But take safety measures while changing fluid to avoid any harm. Otherwise, let skilled people perform this task.


Can you add brake fluid while car is hot? Always apply safety standards when changing or adding brake fluid to your car. The car should not be running or hot. Otherwise, throwing all caution to the wind can bring serious problems to you. There are no negotiations when it comes to following the right procedure. You should always abide by the manufacturer’s recommendations.


Mr. Shafiqule Islam is a graduated Mechanical Engineer and has more than 15 years experience of repairing and maintenance of different brand vehicles like Toyota, Mitsubishi, Ford, Mercedes, BMW etc. He is also giving training to Mechanics. He has started writing to share his practical knowledge to Vehicle Owners, Drivers and Mechanics to keep their cars at best fit.

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