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How to Check Brake Fluid: A Step-by-Step Guide 

How to Check Brake Fluid: A Step-by-Step Guide 

Every part of your vehicle is important no matter what it does but you could make a strong argument that the brakes are one of the most important systems in your vehicle. As important as the battery and the engine are to getting your car started, without a way to stop your car it's a serious danger, right? That's why you need to take care of your brakes as well as you can and keep up with any scheduled maintenance so that they run smoothly and safely. That's for the benefit of both you and all the other drivers on the road. Part of that means knowing how your brakes work including how the brake fluid in your lines works.

Auto Repairs Are EXPENSIVE


If you're concerned about how your brakes have been working lately, maybe they're not as responsive as they should be or maybe you just want to make sure you're on top of everything before it gets to this point then it's good to know how to check the brake fluid in your vehicle.


If you've never had to check the brake fluid before, it may not be nearly as difficult as you think it is.  For people new to DIY car repairs and car maintenance a lot of these jobs can seem intimidating because, for years, this was only the kind of stuff that trained mechanics could do. Nowadays, thanks to the internet, there's nothing you can't learn how to do on your own when it comes to your vehicle. This can end up saving you a lot of time and money in the long run by allowing you to take responsibility for how your car works, and ensure everything is as it needs to be before you need to go to a mechanic to take care of something that may be beyond your skill level. So let's look into how to check your brake fluid, and what to do if there's a problem. 


Do You Check Brake Fluid Hot or Cold?


Before you get started you may want to know if it's best to check your brake fluid levels when your car is cold or when it's hot from running. Some fluids in your car, particularly transmission fluid, are best checked when your vehicle is actually still warm from running. That gives the fluid a chance to warm up and circulate through the entire system. Others, like coolant for instance, you only want to check if the vehicle is cool because of the safety risk to do otherwise. You wouldn't want to open your radiator when it's full of pressurized, hot coolant and have it burst out in an explosion of steam that could cause serious injury.


When it comes to your brake fluid, the best bet for you is to do this when your car is cold. Again, it's a safety concern, and you don't want to be reaching around in your engine when it's hot and there's a risk of injury. Park your car on a level surface and wait till the engine has cooled down before popping the hood and taking a look.


The Right Way to Check Your Brake Fluid


There are a few simple steps that you can take if you're interested in checking your brake fluid. The whole process should only take you a few minutes tops.


Step 1:  Once you have your hood popped and you're looking at your cold engine, you need to find the master cylinder. This may change slightly from vehicle to vehicle but for most cars you're going to find the master cylinder at the back of your engine compartment on the driver side. This should be connected to the firewall, which is the wall of metal that separates the engine compartment itself from the inside of your vehicle. On top of the brake cylinder you should see a brake fluid reservoir. The reservoir is a plastic container that should have a black screw-on lid on top.


 Step 2:  Check the fluid levels in your brake fluid reservoir. Because the brake fluid reservoir is a translucent plastic container, you're able to see the shadow of the liquid inside of it from the outside. This should be the same kind of container that your coolant reservoir is, only smaller and a different shape, but the principle is the same. You can see the fluid level inside and the outside should have markings on it to indicate the maximum fill level and the minimum fill level. Your brake fluid should, of course, fall between those two lines.


It's worth noting here that if you have an older car you may not have this kind of brake fluid reservoir. Vehicles that were made in the early 80s and before probably have a metal reservoir as opposed to this translucent plastic one. If that's the case, then you need to actually remove the cap of the reservoir and take a look inside. That also may sound easier than it actually is depending on the type of car you have. While new brake fluid reservoirs have that easy to use screw off cap, there actually were some models of cars back in the day that had a cap that was securely fastened in place that you have to use something like a screwdriver to pry off. Again, this should only be a concern if you had a much older vehicle.


Step 3:  Take a look at your fluid levels and if everything is okay, either the shadow through the translucent container is between the minimum and maximum fuel lines or you can observe through the cap that you've removed that you have enough brake fluid then everything is fine and you are good to go. Checking your brake fluid is just that easy. 


Now the obvious question left after this is what happens if your brake fluid is actually low. There are two things you need to keep in mind at this point. The first is that you're going to have to add new brake fluid to top up the system so that you have enough. The second thing you need to consider is why you lost brake fluid in the first place. Under normal circumstances you should not be running low on brake fluid. if your brake fluid is low, then that is a good indication that your brake pads have worn down enough that you need to get them if not replaced, certainly checked out by a mechanic.


 What Does Brake Fluid Have to Do with Brake Pads?


The reason low brake fluid indicates you have a problem with your brake pads is one of simple space concerns. Your brake pads press against your wheels when you put your foot on the brakes using friction to stop them. The brake fluid in the lines is what applies the pressure to allow the brakes to clamp down on the wheels in the first place. However, over time your brake pads are going to wear down. As your brake pads wear down, they get smaller. That means the brakes need to squeeze a little bit harder to get the pad against the wheel of your car. So over time, you are going to find that your brake fluid is going to not be able to get the job done because it has to push the brakes a little bit further. 


While the lines were full originally when your brake pads were still full size, they've worn down evenly across four brakes, which means your brake fluid will have to push a few more inches in a system that originally didn't have that much brake fluid in it to cover that extra space. So, at this point, you either need to add more fluid to make up that missing space or get your brake pads replaced to make up the missing space. Arguably you're going to have to replace the brake pads at some point anyway if they're worn down that much, but using a little extra brake fluid to top up the lines will keep you going for a while before that.


 How Do You Add Brake Fluid to Your Car?


Adding new brake fluid to your car is not a very difficult task either but you do need to pay attention to what you're doing specifically because there are several kinds of brake fluid and you absolutely do not want to add the wrong one by mistake. In much the same way that adding orange coolant to green coolant can end up with disastrous results in your radiator, if you add the incorrect type of brake fluid to a system then you could effectively destroy your brakes. 


If you're not sure what kind of brake fluid you have in your reservoir already, you don't want to take a chance by adding the wrong stuff. There are actually a number of different kinds of brake fluid that do not always work together. Different brake fluids are known by the DOT nomenclature which stands for Department of Transportation because they are the ones who set the safety standards and regulations for brake fluid. 


DOT3:  One of the most common types of brake fluid, DOT3 Is glycol base and has a relatively low boiling point. This kind of fluid absorbs water and that means if you open your reservoir to take a look at it, it can actually pull water in from the air which will cause it to fail more quickly. This kind of brake fluid can be used in most vehicles.


DOT4:  This is very similar to DOT3 fluid but has additives that raise the boiling point to make it more efficient. This is also a very common kind of brake fluid and will work in most vehicles. There are also some formulations of this that have enough additives to dramatically raise the boiling point so that it's actually effective in performance vehicles like race cars. The difference between this and DOT3 isn't significant, but your owner's manual will tell you which one is best for your car.


DOT5:  This is not compatible with DOT3 or DOT4 fluid. DOT5 brake fluid is a silicon-based fluid that does not absorb water at all. It's much less common than the other two as well and is typically something most cars on the road don't use.


DOT5.1:  Despite the name, this is more similar to DOT3 and DOT4 brake fluids than DOT5. It's another glycol-based fluid but it has a higher boiling point like DOT5 does.


You need to replace your brake fluid if the level is low or if it appears to be off in some way. If the fluid looks muddy brown or black, you're going to need to have it replaced. This means you have some kind of contaminant in the lines, likely corrosion caused by moisture that has resulted in rust flaking off into your fluid. If you want to be sure you can actually buy brake fluid test strips that you can dip into the fluid reservoir that will tell you what is contaminating the lines. If the fluid is contaminated you're going to need a flush and you should head to a mechanic to get the old fluid flushed from the system and new fluid added. If it's not contaminated, then you can go ahead and add some on your own.


You should use a funnel if you're not confident in the steadiness of your hand when it comes to pouring brake fluid into the reservoir. Brake fluid is both corrosive and toxic, so you don't want to get this on yourself or parts of your engine if you could avoid it.


With a funnel in the reservoir, you can pour in fluid until you reach the maximum fill line. Again, make sure you're using the exact right kind of brake fluid that you already have in the system. If the brake fluid you have is a certain colour, you need to still ensure that you're using the right kind as sometimes different manufacturers will use  the same colour, even though the fluid is not the same. So, rather than matching colour, make sure you’re matching the DOT specifications.


Use a clean rag to wipe up any spills you may have and when you're done reseal the cap securely. That's all there is to it.


The Bottom Line


Few things are more frightening for a driver than to be heading down the road and realize that your brakes are not responding properly. Making sure your brake fluid is topped up to the right level, it's looking clean, and it's the right kind is one of the best ways to ensure that your brakes are going to keep working when you need them to. You never want to be taken by surprise with brakes that give out on you because your fluid levels got too low.