Brake fluid: That hygroscopic liquid

The big word must have thrown many people off balance. Well, the inefficiency or lack of brakes on a vehicle is in reality capable of making one feel the same way. Engine and transmission oil and filter replacement are the usual focus of an average vehicle owner. Some are more religious about it and others, not so much.

Starting and cruising vehicle on the road with shabby performance could be stressful and unpleasant but imagine driving a performance vehicle on the road and being unable to slow or stop it as necessary. As important as the brakes are, most people rarely give it the deserved attention, at best brake pad replacement is considered important.

Recently, while researching content for our weekly radio show which airs on Splash 105.5FM, Ibadan every Wednesday, we went on the streets to sample people’s opinion on if and how frequently they replace the brake fluid on their vehicles. The responses varied from “is that supposed to be changed” “I just top it up” to every three months”.

This underscores the fact that most people are ignorant of the type of care that can ensure the efficiency of the brake systems of their vehicles.

Most people are aware that vehicles are equipped with brakes but oblivious of how it works. Some even have the wrong notions about its workings, while a significant number are misguided or have been misled due to the massive gap between the manufacturers and owners.

An average car weighs in at about 1,300 kilogrammes while empty, to put in perspective, 26 bags of rice or cement. With four adults in it, the weight goes to about 1,600 kilogrammes or 32 bags of rice or cement. Now imagine that much weight, barreling down a road with no effective means of slowing it down! This should only be imagined as a scene from a horror movie.

The major components of the brake system include the pedal, brake booster, brake master cylinder, brake lines and hoses, brake calipers and pistons, disc brake pads or brake shoes, disc brake rotors or brake drums, brake fluid, anti-lock braking system control module, wheel speed sensors and others.

The focus today is on the brake fluid, as it is the lifeblood of the entire system.

Here is how things work: When the brake pedal is depressed by the driver, the force is amplified by the brake booster and transmitted to the brake master cylinder which pushes the piston in it to force the brake fluid to act under pressure to go through the ABS module, if the vehicle is equipped | or straight to the valves from where it is channeled towards the slave cylinder, which is located in the brake caliper. The overall pressure forces the piston in the caliper to act against the brake pads or shoes to push the friction material towards the rotors/disk or drum.

The resistance of the rotors/ drum creates a force that slows the vehicle downs.

The brake fluid is hygroscopic, meaning that it absorbs moisture/water over time, this leads to related corrosion and failure of internal brake system components.  There is no set time to change the brake fluid in your vehicle; timing varies by type of car, the driving conditions, type of fluid and the manufacturer’s recommendations.

It is, however, highly recommended to have it checked during every oil change. The three main types of brake fluid now available are DOT3, DOT4 and DOT5. DOT3 and DOT4 are glycol-based fluids, and DOT5 is silicon-based.  The main difference is that DOT3 and DOT4 absorb water, while DOT5 doesn’t.

Glycol fluids are the most commonly used in 99.9 per cent of motor vehicles of various grades. They are named by their DOT (Department of Transport) coding and are either DOT 3, DOT 4 or DOT 5.1. In general, the higher the number the higher the typical brake fluid boiling point.

The higher the moisture content the higher the chances of boiling, which in-turn leads to gas production in the brake system that could lead to brake failure

The specified fluid type for every car is always written on the reservoir cap for the brake fluid.

Here are a few tips:

Use brake fluid from a sealed container only!

Ensure that you stick to whatever specification is recommended by the manufacturer.

Consider a fluid replacement every 25,000Km.

Your mechanic should have a brake fluid tester, if he doesn’t, review your relationship with him/her.

It is a pleasure to have you here, reading this column. Your audience is highly appreciated, and feedback has been awesome too. Please, do keep them coming.


Hello Doctor, my automatic engine Nissan Altima does not move well when in gear 1.What do I do? (+234803615xxxx).

It would be nice, if you had provided me with further details, such as the year of manufacture and type of transmission. However, I shall address both automatic and manual transmissions.

If your vehicle is a manual/standard shift, inability to move well in gear one is as a result of a faulty clutch system. Your mechanic needs to check out the pressure plate and disc to be sure that the friction material is not worn below the specified level. Please note, if it is, you should replace the pressure plate, disk and release bearing as a set.

If your vehicle is an automatic transmission, the fluid level and quality should be checked to ensure that it is okay. If all is okay and the symptom persists, a mechanic will need to run a computerised diagnosis on the vehicle to be sure that the electro-mechanical components of the transmission are okay. The result of this will advise on the next call of action.


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