Does Brake Fluid Evaporate Over Time?

Break fluid can evaporate, but the rate at which it does so is very negligible indeed, such that its depletion is mostly as a result of either a leak or worn out and damaged brake pads. This negligible rate of evaporation is mainly because brake fluid is not as volatile as most other substances that vaporize easily.

Brake fluids can go bad over time. It is capable of absorbing moisture, which can lessen its overall performance. Because of this reason, it is highly recommended that you should change it at least once every two years or thereabouts. Also,  brake fluid is arguably one of the most vital fluids in any vehicle.

Hence, its evaporation is rightly seen as the last thing you will want to happen since it can lead to a soft brake pedal and a very compromised braking efficiency too.

Despite all these, brake fluid is in a very sealed system, and as a result, the quantity of brake fluid in the car should always remain the same as long as there is no leak whatsoever. However, it can become low when there is any wear in the brake pads.

Should your vehicle run out of brake fluid, it inadvertently means that it will equally run out of brake too. As the brake pads are getting worn out, the level or quantity of brake fluid in the reservoir will also depreciate accordingly.

In this case, if you replace the worn-out pads,  and the pistons are also pushed back to their home positions, the level of brake fluid in the reservoir will also rise as well.

Therefore, brake fluid can evaporate over time, albeit very slowly. Should brake fluid be dribbled down the firewall beside the master cylinder, you shouldn’t fret about it unless you require a concourse perfection beneath the hood.

Again, you may end up doing more harm than good if you try to wipe it off or even flush it out rather than allowing it to dry up on its own. Brake fluid can go low over time, and when it becomes too low, the brake fluid warning light is most likely going to come on. This can happen due to a leak in the brake lines, its calipers, or even the master cylinder itself.

Brake fluid can also get low in the reservoir or tank meant for it when you happen to have hit something along the way while driving.

Conversely, should brake fluid show beneath your car when parked, it is most likely the symptom of a major leak, which should be verified promptly.

In other cases, if your brake fluid is persistently low, there could be a leak, for which reason you should get it flushed or even replaced at least once every year, aside from ensuring that you replace all damaged or worn out brake pads regularly as well.

Depleted brake fluids cause damage to the brake pads, and sometimes, this can lead to vibrations under braking. What is more, noisy brakes are irritating, which could be due to the brake pads or how the brake calipers are engaging when you press the brakes.

Finally, although brake fluid hardly evaporates significantly due to its content of heavy substances that are not very volatile, there are still several ways through which you can lose it unduly.

What causes brake fluid to evaporate?

Brake fluid hardly evaporates as such. In other words, the rate at which it evaporates is insignificant. Despite this contention, some part of it may seem to evaporate mainly due to any small leak that can enable it to be sucked up into the vacuum system, especially if the shift mechanism is vacuum controlled.(Read Also:Can You Get Money From Old Brake Calipers?)

Regardless of everything, some greases can evaporate due to extreme temperatures that will lighten their particles enough for them to become readily volatile.

So, brake fluid evaporates although very negligible, such that what we refer to as evaporation may in reality turn out to be caused by undetected leaks in the system.

Therefore, for what it is worth, your brake fluid can very slowly evaporate where its temperature is raised significantly for its molecules to become very volatile, although the quantity that may evaporate will hardly amount to anything significant such that your braking system may get affected.

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How can I stop brake fluid from evaporating?

It is not very easy to completely stop volatile substances from evaporating except possibly by ensuring that every seals or gasket are in good shape and also installed properly too.

Furthermore, you can also lessen the rate of evaporation of any substance by making sure that its temperature does not get elevated or raised to abnormal levels.

It is for this reason that you are advised to always make sure that damaged or worn out brake pads are changed as at when due, to forestall any excessive heat build-up, which can make your brake fluid evaporate even though that has a very insignificant impact on your overall braking power.

Does brake fluid evaporate monthly?

As was discussed earlier in the article, brake fluid rarely evaporates, and if it does, the quantity of it lost in this way will not amount to much.

Therefore, how much of it evaporates will depend on the prevailing factors discussed above rather than the length of time it will take.

All the same, brake fluid can be lost due to evaporation monthly, but all the conditions that will catalyze this will have to prevail in the system first. (Read Also:Does Brake Fluid Stop Power Steering Leak?)

So, yes, your brake fluid can evaporate monthly, if you allow it, but that rarely happens, and where it does, the quantity of brake fluid lost in this manner will not affect your braking efficiency unless the fluid is lost through other means as well.

What should I do to stop brake fluid from leaking?

There are several measures to take that can prevent your brake fluid from leaking. First, make sure that you replace all damaged and worn-out brakes pads and calipers, as soon as you identify any defects in them.

Second, you should also make sure that worn-out or damaged seals or gaskets are promptly replaced too. To this effect, you should always inspect the car along the routes where brake fluid is likely going to leak out.(Read Also:Can Brake Fluid Be Used As Penetrating Oil?)

If you are up against these possibilities, there is a pretty good chance that you will be able to stop your brake fluid from leaking.

Does transmission fluid evaporate?

No, transmission fluid does not evaporate because it hardly burns off like most other oils. Consequently, transmission fluid does not evaporate, but there is more to it.

This simply implies that any low transmission fluid in the car is possibly caused by factors other than evaporation. However, transmission fluid can break down as a result of friction and excessive heat.

The moment this starts to happen, your transmission fluid won’t serve properly as it ought to, and it is also possible that it will generate deposits that can undermine the driveability of the vehicle entirely too 

Frequently asked questions(FAQ)

How long can brake fluid be exposed to the air?

All things being equal, brake fluids can be stored for up to a certain length of time and not for much longer than that. To this effect, most brake fluid manufacturers recommend that any opened can of DOT brake fluid should preferably be used up in at most twelve months after opening, or had better be discarded entirely. (Read Also: Does Brake Caliper Position Matter?)

This is because, if you expose brake fluid to the air, it is capable of absorbing moisture, thereby reducing its boiling point and also the upper-temperature tolerance of the braking system of the car. In extreme case scenarios, very contaminated brake fluid can cause a loss in the braking power of the vehicle.

Is it okay to store brake fluids?

It is okay to store brake fluid, but not for any time longer than the manufacturers say it is allowed, and under all the recommended conditions too.

First, brake fluid is best stored in its original container in clean, dry places, and at or below room temperature also. Most preferably, it should be stored separately from other petroleum products or fluid substances used in regular maintenance because of its hygroscopic nature.(Read Also: Do Brake Lines Get Hot?)

Bottles of brake fluids may not bear any expiration dates. This simply means that brake fluid does not break down over time as most substances do, aside from the fact that it can maintain the same level of performance even many after years of storage. However, care should be taken when the can is opened.

Does Brake Fluid Evaporate Over Time – Conclusion

Brake fluid will appear to be volatile since it can be seen to progressively reduce in its tank. However, a close inspection is most likely going to indicate that the fluid is actually being lost due to other prevailing factors and not just evaporation.

In most cases, your brake fluid can leak due to either damaged or worn-out brake pads, as well as damaged seals or gaskets. Before you can ascertain which one of these is the culprit for your brake fluid losses, you should meticulously inspect the car along with all the places where you expect to identify the fault.

If you have a problem doing this effectively on your own, the user manual of the vehicle will come in handy here. Alternatively, you should consult an auto specialist on the matter.