A low brake fluid level is usually the first tell-tale sign that there may be a problem with the brake system.
The whole system is a closed-loop so, if everything is OK, little to none should be missing over a longer period of time.
If a low brake fluid level is present more frequently (for instance you have to add some once a month) then you certainly have a problem.
This article might help you in noticing and finding what that problem may be.
LOW BRAKE FLUID LIGHT-FIRST SIGN OF TROUBLE
Once the level of brake fluid gets low, the warning light will come up on the dashboard (thanks to a sensor located on the container cap).
There are various types of dashboard warning lights for a low brake fluid level.
On older types of cars (but on some modern also) the parking brake light and the low brake fluid light are the same. This may cause a bit of confusion and perhaps a delay in reacting to the problem on time.
So, if the warning light is the same and there’s a low level of brake fluid, it will come up and stay on even when the parking brake is released.
To avoid such confusion, many manufacturers have made a separate warning light on the dashboard.
Sometimes even a combination of warning lights will come up (for instance ABS and parking brake light together).
On most modern dashboards, with info screens, the low brake fluid message will be displayed in written form so there’s no confusion.
Whatever the case may be, it’s best to know the purpose of all the warning lights on the dashboard
(click here for a separate article on that topic).
Besides the warning light, checking the brake fluid level on a regular basis is one more way of spotting a problem on time. If you’re not sure how to do this, click here and find out.
LOW BRAKE FLUID SYMPTOMS
As mentioned, the car brake system is a closed hydraulic system where proper fluid pressure is crucial.
The brake fluid transfers power from the brake pedal on to the brake cylinder and then to the calipers or wheel cylinders which then press brake pads or brake shoes against discs or drums.
This a brief explanation, for a more in-depth one on Wikipedia, click here.
So, a low brake fluid level will decrease the pressure in the system meaning lack of braking force, and perhaps more important, timely reaction.
Main symptoms that you’ll encounter:
The brake pedal gets soft and smushy-like
This is the first and most obvious symptom. Every driver who uses his/her car every day knows that there is a constant level of resistance when pressing it.
First, the problem is barely noticeable (only experienced drivers notice in most cases). Later, as the fluid level lowers, the pedal becomes softer and softer.
At the same time, a decrease in braking force will occur.
In the final phase of the problem (which should never be allowed to happen) you’ll have to pump the brake pedal a few times to achieve braking power.
Brake fluid leaks
The moment you notice a low brake fluid level, check around the car for leaks. The leaks are usually small and hard to spot at the beginning of the problem. As it progresses you may find stains under the car, usually near the wheels.
Dirty brake fluid
If you happen to check the fluid, it will not have the regular clear, honey-like color, rather a more dim and fizzy look.
So to recap on this part and the symptoms that will appear:
The brake pedal resistance is not usual, it’s a bit softer
The low brake fluid light comes up
As the problem gets worse, the brake pedal gets softer and more smushy
The final phase of the problem is that the brake pedal goes almost to the floor with little resistance. To achieve braking power, you have to pump the pedal several times.
This is the common scenario and usually happens in this order.
COMMON CAUSES OF LOW BRAKE FLUID
1. Worn out brake pads
Brake pads have the function of squeezing the brake disc thus slowing down the wheel. They logically wear out over time as the friction material on the pad is softer than the disc.
The level of brake fluid in the system is calibrated when the brake pads are new. As they wear out over time, the level of brake fluid goes down.
Adding some during this period, as the pads naturally wear out is normal.
Nevertheless, when you see a low brake fluid level in the container, check your maintenance record for when the pads were replaced last time.
2. Worn out brake shoes
Same story as with the brake pads.
Brake shoes wear out over time, so a low level may mean you should check when they were last replaced.
3. Worn out or faulty brake cylinder
Brake cylinders transform hydraulic pressure into kinetic force.
More simply put, they are the part that pushes the pads and brake shoes against the disc or drum.
These kinds of problems are pretty rare since almost all modern cars have brakes discs and calipers on all four wheels. Calipers are also a type of brake cylinder. They are robust and seldom cause problems.
Master cylinders also rarely malfunction. Caliper and master cylinder malfunctions are usually present in older or high mileage cars.
More common problems of this sort come from drum brakes. The wheel cylinder inside the drum (that pushes the brakes shoes against the drum) is a weak spot on a lot of cars.
4. Damaged or punctured brake lines, loose or faulty connections
The brake lines are a combination of metal, durable rubber or plastic hoses and pipes.
Larger parts of the brake lines are located under the car making it susceptible to road conditions, weather, and physical damage.
When this is combined with material fatigue it’s no surprise that the brake lines can give in overtime. This is why it mostly happens on older cars or ones that suffered some kind of physical damage, like an accident for instance.
Hot spots for problems are points like where the metal pipes connect with rubber or plastic hoses, where the hoses are stretched or turned (like near the wheel hub), or where the lines are connected to the brake cylinders.
The problems are noticed mainly by a low brake fluid level as well as smaller or larger leaks.
5. Overheating car brakes
To be clear, overheating the car brakes will not immediately cause a low brake fluid level.
But if the brakes are overheated constantly (like in a long downhill drive) the whole system may get damaged.
Also, the brake fluid is sensitive to overheating as it starts to lose its properties and density.
This leads to a higher possibility of leaks, or even worse eventual loss of braking power.
If this happens, it’s best to check the whole system and replace the brake fluid completely.
For more information on brake problems and symptoms click here for a separate article on that topic.
CAN YOU DRIVE A CAR WITH LOW BRAKE FLUID?
If the car has some serious braking power left, yes, but with extreme caution. If the leak or damage isn’t too severe, tray adding some brake fluid before you start driving.
This way, maybe, the brake power will hold until you reach a garage or place where you can fix the problem.
With a low or non-existent level of braking power, best don’t drive. Call a towing service or let someone tow you with a towing bar. It takes time, but better safe than sorry.
But, as we all know, the situation on the road may be that you might find yourself on a remote road, nobody wants to stop or no one has a towing bar. You’re simply left to on your own.
Well in this case there is a way out, again if there is at least o bit of braking power left.
This procedure demands some serious driving experience, a cold head, and good reflexes.
Also, make sure to stay clear of highways and main roads as much as possible. If not, take the slow side lane and be sure to turn on the hazard signals.
If you happen to have some braking fluid, add some before you start. As mentioned it will maybe give some more pressure in the system.
Be always aware that, especially if the low brake fluid problem is in the final stage, you’ll have to pump the brake pedal a few times before achieving some braking power.
This is important as you have to be extra careful about the road conditions and to avoid any close contact with other vehicles or obstacles.
Combined with the brake pedal, you can use the handbrake to additionally slow down the car.
This is done by constantly holding the release button and pulling the brake so it doesn’t get jammed by the locking mechanism. To put it more simply, the handbrake shouldn’t click while you pull it.
Much resembles an old fashioned horse carriage brake if you’ve encountered such.
So, in real life, it looks something like this:
If you have some brake fluid, add before starting the drive
Start the car and pump the pedal to achieve some braking power
Try to plan your route to avoid highways or high-speed roads. If you have to use them, use the slow side lane to get out of harm’s way.
Turn on the hazard lights and fasten your seat belt
Start driving slowly and keep a safe distance from other cars as much as possible. Drive as slow as possible. This will give you more time for reaction.
If the pedal is getting softer, use the handbrake for additional braking. Keep the release button pressed when using it.
Use engine braking as much as possible, for additional slowing down. Accelerate only as much as you have to.
When the destination is near, start slowing down and breaking from afar. This way you’ll be able to stop safely.
Well, as you’ve probably concluded, pretty much a circus act and a risky and complicated one as well.
But if there’s no other way, it may help.
Again, do this only in case of an emergency and if there isn’t any other available way to get out of trouble.
Brakes are the most important system on the car in terms of safety, both yours and other participants in traffic.
Keeping the brakes in the best possible condition is the obligation of every driver. If not being able to fix it, then at least to notice problems on time.
A low brake fluid level is the first tell-tale sign of problems and a big warning signal that repair or inspection should be done as soon as possible.
As mentioned in the beginning, an annual adding of brake fluid is normal, but adding some every month or less is a problem for sure.
In the end, make the car check-ups a regular habit of yours. It will let you notice problems on time, low brake fluid level, or else.
Written by: Sibin Spasojevic
Former car technician, life-long car and DIY enthusiast, author for Despairrepair.com