We see a lot of cars coming through that have well used brake fluid in their systems, unfortunately it is often an item that is overlooked when folks think about maintaining their vehicles, and it is inexpensive to get a brake flush done and it will have your car in a safer position to handle what the road will throw at it.
First, a general explanation about brake fluid, it’s properties and what it does. In general we’ll be talking about DOT 4 type brake fluid, and while there are some others out there with differing properties, DOT 4 tends to be the most widely used currently. DOT 4 brake fluid is a hydraulic fluid that is not appreciably compressible, is hygroscopic(attracts moisture), and has a dry boiling point of 446 deg F and wet boiling point of 311 deg F. The “wet” boiling point is defined as when the fluid has 3.7% moisture content. More on that in a minute.
Essentially, when you push your brake pedal, the fluid gets pushed through the system, and pushes the brake caliper pistons which push your brake pads together onto the brake rotor to stop the vehicle. A properly working system with fluid that is within specification will be able to handle all expected braking conditions without any danger of brake fade, failure or any other type of mishap. The key element for the specification of the fluid is measuring it’s moisture content. We have a special tool that does this for us, and we recommend that fluid not be allowed to reach 3% moisture content. Heres why:
One of the key elements of the fluid is it’s ability to withstand the high levels of heat that are generated while braking. The main aspect of this is that your brake fluid should be able to handle any conditions that get thrown at it. Remember we talked about the wet boiling point? When brake fluid boils, it vaporises into a gas, and loses all of the non-compressible qualities that it had while it was in its liquid form. So this means that it is no longer pressing the brake pads against the rotors, and thus no longer slowing the vehicle. This usually occurs during a heavy braking situation where you probably REALLY need your brakes to be working at their best. And this is the key to having the system functioning as it should. With brake fluid that has 3% or more moisture content, your braking system may seem to work fine with no noticeable symptoms. But your brake fluid is not ready to handle all situations as it should, so encountering those heavy braking situations will potentially lead to the boiling of the fluid and a loss of braking ability.
The additional benefit of flushing your brake fluid is to keep all of your braking components free of corrosion and rust that can occur when the fluid has a high level of moisture content. We recommend that your vehicle have its brake fluid flushed when it measures 2% of moisture content, or every 2 years.
Stay tuned for more pro tips, and as always, we’re here for you and are happy to answer any questions you might have.
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