Can You Add Brake Fluid While the Car Is Hot?

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Adding brake fluid to a vehicle is one of the simplest jobs. But the question is, can you add brake fluid while the car is hot?

Yes! You can add brake fluid to your car even when the engine is hot, but be careful not to spill it on the hot engine parts or breathe in the fumes. Avoid overfilling the reservoir, and always follow the owner’s manual guidelines while adding brake fluid.

Add Brake Fluid While the Car Is Hot

Although it’s better to allow the vehicle engine to properly cool down before trying to add brake fluid, you can still do it while it’s hot if needed. This article explains the consequences of adding brake fluid the car is hot.

Can you just change the brake fluid without bleeding?

No, you cannot simply change the brake fluid in a system without bleeding. It is important to bleed the system before adding new brake fluid. Bleeding is important because, over time, water can accumulate in the system, and you need to remove it to achieve the best performance of your brake system.

When you drain the old brake fluid, air and contaminants may enter the system. Therefore, bleeding is essential to eliminate the air and any dirt particles.

Can you add brake fluid while the engine is hot?

Yes, you may add brake fluid when the vehicle is hot, but it is not suggested because when brake fluid droplets fall on the hot parts of the engine, they may produce smoke or start a fire.

Brake fluid has a high boiling point, but when it achieves that point, it may turn into gas, creating air bubbles in the brake line. These bubbles may make the brakes less effective and unsafe. Therefore, you should let your vehicle engine to cool down before pouring brake fluid.

Another risk is that if the hot brake fluid comes into contact with hot engine parts, it can produce smoke or even start a fire. The engine’s metal parts retain heat and can cause severe burns if accidentally touched while trying to add brake fluid.

To stay safe and keep the brakes working well, always wait for the vehicle to cool down completely before adding brake fluid. This way, you can prevent accidents and make sure the brakes work properly.

How to Check Car Brake Fluid?

Checking brake fluid is a straightforward process. If you are familiar with adding brake fluid to your vehicle, then you know very well where to begin.

Brake Fluid Level

Follow the below-given steps to check car brake fluid:

  • Park the vehicle: The first step is to park the vehicle on a level surface to ensure an accurate reading without any disturbance.
  • Turn off the engine: Turn off the engine and let it cool down.
  • Find the Fluid Reservoir: When the engine is cold down, find the brake fluid reservoir. The master cylinder, where the brake fluid is stored, is usually easy to find. It is recommended to consult your owner’s manual to find exactly the location of the fluid reservoir.
  • Open the fluid reservoir: In most cases, the reservoir is transparent, allowing you to check the fluid level without opening it.
  • Check the fluid level markings: Look for two marks on the reservoir. One represents the maximum brake fluid level, and the other represents the lowest level.
  • Verify the fluid level: Make sure the fluid level falls between the minimum and maximum markings. If it’s lower than the minimum mark, you’ll need to add more fluid. However, if it exceeds the maximum mark, you should discharge the extra fluid.

Read More: How to Flush Brake Fluid?

What happens if I overfill the brake fluid?

brake fluid reservoir

Overfilling brake fluid creates unnecessary pressure within the braking system of your vehicle, leading to weakened seals and potential failure. This may also cause the brake pads to rub against the disc, resulting in accelerated wear and overheating of the entire brake system.

When your brake system has excessive pressure, it may lead to premature failure of the seals. 

It’s essential to be cautious about the amount of brake fluid you add and ensure it remains between the minimum and maximum marks to avoid overfilling. By maintaining the correct fluid level, you can prevent premature system failure and ensure the brakes function properly.

Why You Shouldn’t Add Brake While the Vehicle is Running?

Adding brake fluid while your car is running can lead to a chemical reaction with the metal parts of the braking system, resulting in corrosion and potential damage to the whole brake system.

Furthermore, adding brake fluid while the engine is running is not safe while driving. It can lead to excessive pressure in the brakes, causing them to lock up and potentially causing an accident. Therefore, it’s important to avoid adding brake fluid while the car is running to ensure both the longevity of the brake system and your safety on the road.

How Long Will Brake Fluid Last?

The service life of the brake fluid level depends on different factors. The average service life of the brake fluid is from 2 to 3 years or every 45,000 miles. However, this duration is also influenced by the car’s usage.

Busy or high-mileage vehicles may require more frequent brake fluid checks compared to those driven moderately. Refer to the vehicle’s service manual provided by the original equipment manufacturer for specific details, considering both time and distance factors to determine when to add brake fluid.

FAQ Section

Why shouldn’t you ignore a low brake fluid level?

The brake fluid ensures the efficient performance of your vehicle’s braking system. It prevents the system from overheating and helps to quickly stop the vehicle. When the brake fluid level becomes low, it may lead to overheating of the brake system, unusual noises, reduced performance of the brake system, and premature failure of the system. Therefore, you shouldn’t ignore a low brake fluid level.

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

Safety should always be a priority, especially when working with brake fluid. Before trying to add brake fluid, it’s essential to let the vehicle cool down. On average, this process takes about 20 to 35 minutes, although some cars may require up to one or two hours to cool to a safe level. Once the car has cooled, it’s crucial to know the correct method for adding brake fluid to the reservoir to avoid any mistakes or accidents.

How often do you really need to change brake fluid?

The service life of the brake fluid depends on different factors, including the vehicle model, driving conditions, and manufacturer’s recommendations. Most manufacturers recommend changing brake fluid every 30,000 to 45,000 miles or every 2 to 3 years. This recommendation considers that brake fluid is hygroscopic, meaning it absorbs moisture from the air over time. Moisture in the brake fluid may lower its boiling point and lead to reduced braking efficiency.

Can I mix old and new brake fluid?

Yes, you can safely mix new and old brake fluids as long as they have a similar chemical composition. However, ensure the old fluid is not too degraded or low in the reservoir before adding the new one. The general rule is to add the old fluid with a small quantity of the new fluid using the appropriate method to add brake fluid to your vehicle.

Should a car be running when adding brake fluid?

No, your vehicle shouldn’t run while trying to add brake fluid. Adding brake fluid is a simple maintenance task that assists the braking system to work efficiently.

What to do after adding brake fluid?

After adding the new brake fluid, it’s essential to pump the brakes to force the fresh fluid to enter the brake lines and create hydraulic pressure. Pump the brakes around 30 times or until you feel the pedal engaging.

What happens if you put too much brake fluid in a car?

Avoid adding too much in the brake fluid reservoir, as the brake fluid is in a sealed system, and additional fluid may produce unwanted brake pressure as it expands due to heat. This pressure could lead to the brakes being slightly applied even when you’re not pressing the brake pedal. Prioritize safety and follow these guidelines for maintaining your brake system effectively.

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Written By

Engineer Rahela

Rahela is the owner and main author of Mechanicalspecial. She is an automotive expert writer. She have over four years of experience in the automotive writing niche and have completed over 700 pieces of content from 40 projects. She have good knowledge and skill in vehicle repairing, all mechanical work, car upgrades and maintenance.

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