Is Brake Fluid Hygroscopic: Why, How and Detailed Facts:

In the automobile sector for braking safety “Is brake fluid hygroscopic” is one of the most interesting and common factor. In this article is brake fluid hygroscopic and its related several factors are discusses.

Most of the brake fluids which are available in the vehicle’s breaking system in braking safety such as DOT 3, DOT 4 are hygroscopic. The term hygroscopic define the ability for absorbing the moisture when the breaking fluid is exposed to atmospheric air. The most unwanted situation is to taking moisture from air.

The meaning of hygroscopic for a brake fluid is in every 32000 miles in the brake fluid flushing should be definitely present thus the moisture can be removed by the brake fluid. But in case extra amount of water is present then it will be lower than the boiling point. When the pedal of the braking system is pressed the brake fluid start to vaporized boiling point of the brake is lower than the usual boiling point. Functionality is reduced for this reason.

In the automobile sector a verity of fluid is uses for the different type of operations. These fluids are carried different type of properties. Different types of chemicals are present in theses fluids for performed different type of operations among them hygroscopic is one of them and created unwanted situation.

Is brake fluid hygroscopic
Brake Fluid Hygroscopic

Why is brake fluid hygroscopic?

In automobiles, light trucks, bicycles, motorcycles mainly in automobile sectors hydraulic fluid is applied in clutch and brakes which are also in hydraulic type this particular fluid is known as brake fluid.

The fluid substances which are glycol based like DOT 3, DOT 4, and DOT 5.1 they are actually hygroscopic. The term hygroscopic means the normal pressure in the atmosphere absorbing moisture or water. The rate of the absorbing water or moisture can be 2-4 % per year.  This hygroscopic condition is actually created unwanted situation in climate or humid situation.

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The water or moisture in the brake fluid goes through the microscopic pores into the brake house, seams, joints and seals. The moisture or water in mixed up with brake fluid and reduce the temperature of the boiling point and decreases the performance of a hydraulic vehicle.

Moisture or water is main obstacle for the brake fluid. The brake fluids can absorb the moisture from the brake and brake fluid reservoir. The brake fluids can absorb the moisture even the vehicle is not running.

What are the advantages of brake fluid being hygroscopic?

By the help of brake fluid force is transferring from force to pressure and also amplify braking force in the vehicles.

The advantages of brake fluid being hygroscopic is briefly summarize in below sections,

  1. Water pooling of the brake system can be preventing localized corrosion of the system’s internal parts.
  2. When the moisture or water enter to system of the vehicle alternatively in the pooling of low spots, for this reason the comparison weight of the brake fluid is dispersed throughout the whole amount of the brake fluid.
  3. Sometimes in braking system mineral oil is used as a brake fluid.
  4. Mineral water is not hygroscopic this is actually hydrophobic and this condition not absorbing any moisture or water from the atmospheric. In this particular situation boiling point remains constant and the boiling point never drop.

This brake fluid can work only because of the liquids present in the vehicles are incompressible. When we simply applied our foot for brake the pedal of the vehicle that time in the rear brakes and front brakes simply the brake fluid transfer force to presser and helps to stop the running vehicle.

Where does brake fluid absorb moisture from?

Certain characteristics are present in the brake fluid and should have certain standard quality thus the brake fluid can work properly in the system of the brake.

Now a days in the in the automobile sectors glycol ether is used as a brake fluid. The glycol ether brake fluids are generally hygroscopic type, that’s mean from the atmosphere moisture or air is absorbed. Moisture is absorbed by the brake fluid when the system of the hydraulic brake is exposed to the atmosphere.

By the help of microscopic pores of the seals, joints, rubber hoses the brake fluid of the hydraulic braking system is absorb. When the humidity is too high the main problems are arise.

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The brake fluid can vary where the temperature is higher than the normal temperature especially for the disk brake caliper, drum brakes and also wheel cylinder of the drum brake. The brake fluid should have high boiling point that it could not vaporized in the boiling point. In the braking system vaporization is one of the major problems because it tends to high compressible relative to liquid substance and as a result the pressure is converted into force and running vehicle tends to stop.

How quickly does brake fluid absorb moisture?

The level of brake fluid in a hydraulic breaking system can be low for some leakage should be present in the system. As a result pressure loss is occurring in the system of hydraulic brake.

The brake fluid absorbs air or moisture from the atmosphere per year about 2-3 %. The amount of moisture or water is absorb it’s depend upon the temperature and operating condition of the hydraulic breaking system.

The performance ability for the hydraulic brake is decreases. In the modern vehicle system two circuits are used for avoid this unwanted situation. One circuit is attached to the front brake and another is attached with the rear brake.

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How to reduce hygroscopic brake fluid?

An engineer designed the brake fluid as this way where the metal which is used in the braking system can protect.

The examiner of the automobile sectors they exam the brake fluid in various way to understand how to reduce hygroscopic brake fluid? And come to a concussion that, the brake fluids which are actually glycol based such as DOT 3, DOT 4, should be replaced or flushed in every two to three years. The brake fluid when fail for water or copper content test.

The brake fluid is used inside the ABS control valve, wheel cylinder, master cylinders, and calipers. The inside corrosion is protect by the brake fluid. Additives are used for delay the process of corrosion. 

Water content is increases in the system three and a half percent that time brake fluid definitely should to change and install a new one factory specified fluid. The new installed brake fluid always should be stored in a container which will be sealed thus it could protect the moisture or air. For safety purpose always should to check the condition of the brake fluid for the hydraulic braking system.

Effect of hygroscopic on brake fluid:

Brake fluid is very important factor when it’s come to safety factor for the vehicles.

Water amount of the braking system’s brake fluid is increases for this reason the boiling temperature is decreases. Brake fluid contained lots of characteristics among them hygroscopic are one of this. The characteristic hygroscopic means tends to absorb air or moisture during the life period for the vehicles through the joints, pipe, and hoses.

Brake fluid
Brake fluid
Image Credit – Wikimedia Commons

Automotive Service Excellence technician are at first need to inspect the condition of the brake fluid and also check the level of brake fluid. For annual basic the condition and level always should to be checked.

Frequent Asked Questions:

Question: What situation is appear when the temperature of brake fluid is too high?

Answer: The master cylinder of the hydraulic braking system is overfilled then the brake fluid cannot get enough places to expand for the expansion of heat.  A residual drag is appearing for expansion of brake fluid.

When the temperature is too high noise, squealing, vibration while braking, leakage of the fluid theses unwanted conditions are arise and it should not be  neglected.

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