Commonly Overlooked Maintenance Items 3

Last month I talked about transmission fluid, this month I will talk about one of the most commonly overlooked fluids, brake fluid. You may be thinking, “I have never heard of needing to change brake fluid.” Well, you should. Most people think just because the car stops the brake fluid is fine. This is not true. I will explain brake fluid’s job, why you should change it, and how to change it.

First, brake fluid has one job and that is to help you stop. Brake fluid works by using hydraulic pressure to push it from its reservoir to the brakes. Brake fluid does not compress like other fluids. This is one of the main reasons to change your brake fluid. The fluid is hydroscopic. This means that it absorbs water from the air. Water compresses easier than brake fluid. If your brake fluid has water absorbed into it, then your braking efficiency is decreased. To help decrease any chances of water contamination, make sure you don’t leave the reservoir cap off for long periods or leave the cap off a bottle of brake fluid. You should also not use a bottle of brake fluid that has been opened after it has sit on the shelf for a long period of time. Besides decreasing braking performance, water contamination can cause rust in the brake components.

Brake fluid, just as other fluids, breaks down over time. Brake fluid is not cycled through the braking system like other fluids. What this means is that fluid at the end of the line or closes to the actual brakes, goes through temperature changes by being heated by the braking process. This breaks the fluid down faster. This is one reason why the brakes should be bled anytime the brakes are serviced.

So now you know what it does and why you should change it - but how do you change it? It is a simple process. First, make sure you consult a shop manual to make sure of the procedure. What I outline here is the most basic procedure. You want to make sure not to screw up any ABS systems or traction control systems while doing this. If you don’t feel comfortable doing it, take it to a professional.

The tools you need depend on the vehicle, but the most basic shop tools will work. You will also need plenty of new brake fluid. You can buy brake bleeder kits from the most basic to professional level. Mityvac (http://www.mityvac.com) makes some great kits for this purpose. The procedure I will show you uses only basic tools.

You need to jack the car up and take the wheels off. You can take one wheel off at a time to do this. You want to start with the wheel that is furthest from the master cylinder. This is usually the passenger side rear tire. Locate the bleeder screw and find the right size wrench. Next, get a clear plastic tube and a clear bottle. Pour in some fresh brake fluid and put one end of the clear plastic tube in the bottle making sure it is submerged the brake fluid. Attach the other end of the hose to the bleeder screw. Open the bleeder screw and have someone pump the brakes. Make sure they do this fairly slowly. This will force the old brake fluid out and replace it with new brake fluid. Make sure the reservoir stays full or you will introduce air into the line and need to start over again. Once the old brake fluid is replaced by the new brake fluid, close the bleeder screw and repeat the process on the next wheel that is the furthest away from the master cylinder. This procedure should be done every 60,000 miles.

The fluid that your vehicle uses depends on the vehicle. Brake fluid comes in 3 designations DOT 3 DOT 4 and DOT 5. DOT 3 and 4 are the most common. DOT 5 is a silicon brake fluid. You can find out what to use by either looking on the reservoir or your owners manual. DOT 5 can be used in both DOT 3 and DOT 4 systems, but to take advantage of the improved DOT 5, you must completely remove all DOT 3 and 4 fluid. The DOT 5 fluid has higher boiling points and extended life characteristics. Be careful as some companies don’t recommend DOT 5, but most aftermarket brake companies do recommend it.

So as you can see, there is reason to change your brake fluid. Next month we will talk about the remaining fluids. If you have any questions, please let me know. Also, if you have any suggestions for future articles, drop me an email with those suggestions.

Vincent Wright
sales@kmwperformance.com
http://www.kmwperformance.com