ALT-1 How to Check Brake Fluid
Many people overlook checking the brake fluid in their car, and then wonder why brake system repairs are so expensive. Checking the brake fluid only takes a couple seconds, and can save you thousands of dollars in repair bills.
Brake fluid does not "wear out." Some kinds of brake fluid become contaminated with moisture and if your brake fluid is dark then it is most likely time to change it.
Brake fluid should always look exactly as it did when it was poured out of the bottle. There are several types of brake fluids and not all of them absorb moisture. The brake fluids that do not absorb moisture, DOT5, are permanent, meaning they never need to be changed or maintained unless there is a leak.
How to check the brake fluid
The master cylinder is at the end of the brake pedal in almost all vehicles so your first job is to locate it. On most cars it is under the hood on the driver's side against the firewall. There is a black cap on it that specifies to use only a certain type of brake fluid in the reservoir.
Do not get the brake fluid reservoir confused with the hydraulic clutch fluid reservoir that comes on vehicles with standard transmissions. Sometimes they both get fluid from the same reservoir, but not always, so make sure that you have the right one. Then you can remove the cover from the brake fluid reservoir and check the level. The brake fluid level should be about 3/8 of an inch from the top of the reservoir, and there is usually a set of marks to go by in the side of the brake fluid reservoir to make things easier. If the fluid is low, then it might be an indication of needing some new brakes, or an indication of a brake system leak, if the (BRAKE!) warning light is on.
If there is a float in the master cylinder reservoir, then there will also be a low brake fluid warning system in your car. If the fluid is full, and this light is on, then the float is either stuck or bad. Both are common problems. Make sure that you are not dealing with a leak, or a need for new brake linings before adding any fluid to the system, because they are specifically designed to only hold so much fluid.
Now that you know about how to check the level of the fluid, we will look into the dark color or muddy looking brake fluid that only happens on DOT3 brake fluids.
The dark color is water that the brake fluid has absorbed. This is a normal part of how it works, but it should be monitored. At the auto parts store, there are brake fluid test strips or litmus strips; these can be dipped into the fluid so you can check the quality of the fluid. Remember this applies to DOT3 brake fluid only. Fewer cars are coming equipped with DOT3 brake fluid every year and the problem will soon take care of itself.
DOT5 brake fluid actually repels moisture, and that makes hydraulic brake system parts (the expensive ones) last longer. You can replace a higher number brake fluid where it calls for a lower number. This means DOT4 and DOT5 are acceptable in DOT3 systems. However you cannot replace a lower number fluid when it calls for a higher number fluid. So, that means that DOT3 fluid cannot go in a DOT4 system. You should never mix brake fluids either. If you make the conversion to a newer fluid, make sure to only use that kind of fluid from that point forward.
