Brake Maintenance • An Informative Post

Brake system flushes… explained.

Most will agree that the hydraulic braking system in all modern road-going automobiles is the most important system in your car. If you are reading this there is a good chance you are an automotive performance enthusiast and love to go fast, but when the time comes to yield to traffic, take a hard corner or just slow down and cruise… you need a means of shedding that speed.

In order to fully explain the importance of flushing the brake system of your vehicle I must first ensure you have some background of how the system works. The hydraulic system in a vehicle consists of a pedal actuated “master cylinder”.  The master cylinder is essentially a piston inside of a housing, when the pedal is pressed the piston moves and pushes hydraulic fluid out of the ports in the housing. There are then lines (hard metal tubing and flexible rubber hoses) that connect to the caliper (disc brakes) or slave cylinder (drum brakes, which are rare these days). As the hydraulic pressure is applied to the caliper or slave cylinder the caliper pistons squeeze the pads around the rotor or the slave cylinder pushes the shoes outward into the drum. This pressure creates friction and turns motion into heat and you slow down.

Now this is a VERY simplified explanation of the braking system. There are vacuum and hydraulic assist systems that increase braking power and improve feel without making the pedal feel like you are stepping on a brick. There are also ABS systems which use sensors for wheel speed and a pump to pulse the brakes to keep the brakes from locking up and initiating a skid. But for our purposes the simple hydraulic system explanation will do.

Now, brake fluid is hygroscopic. “What the heck does that mean?” you may ask. Well, according to Merriam-Webster:

Hygroscopic adjective hy·gro·scop·ic : readily taking up and retaining moisture.

So, brake fluid absorbs water. What does this mean for the braking system and in turn us, the driver? Well, for the braking system which is made from primarily metal parts, as the level of water absorbed into the fluid rises so does corrosion. The more water in the brake fluid the faster the pistons in the master cylinder, calipers and/or slave cylinders, along with the lines and expensive ABS pumps will form corrosion, necessitating rebuild or replacement.

Another by-product of increased moisture levels in brake fluid means a lower boiling point. Now as discussed earlier, braking systems turn motion into heat. That heat goes into the rotor, pads and caliper (or drum, shoes and slave cylinder) and that heat inevitably makes its way into the fluid. Now when the fluid is saturated with fluid and the boiling point is lowered the fluid can actually boil inside the caliper or slave cylinder. When a fluid boils it turns into a gas. Fluids cannot be compressed, gasses can be. The gasses within the hydraulic system cause what is commonly called “Brake Fade”. Brake fade is that frightening moment when you are braking HARD and out of nowhere it suddenly feels like there is an excess of air in the system and the pedal goes to or close to the floor, causing a panic in most drivers.


On the other side of the “water absorption” coin, the more water that is in the system, the more susceptible the fluid is to freezing in very cold weather. This can cause many different issues from a very hard brake pedal in cold weather, all the way to burst lines from hydraulic expansion as the fluid freezes.

So, that all being said most European auto manufacturers state the fluid flush interval should be 2 years regardless of mileage. So this is a time dictated service, the fluid will absorb just as much water in 2 years whether the car sits un-driven or accumulates 100,000+ miles.

Here at Excelerate we highly recommend sticking as close to this 2 year replacement interval as possible. The braking system is THE most important safety system in your vehicle and avoidable repairs can become very costly. We use Motul 5.1 exclusively (unless otherwise specified by the manufacturer) and have a Power Probe brake bleeder which keeps constant pressure on the hydraulic system and has a large reservoir of fresh, clean, hermetically sealed brake fluid so the master cylinder reservoir cannot run dry while being bled.


How Can You Take Advantage of This Service?

Would you like to potentially schedule an appointment? Maybe you would like to gather some more information about this service before making any commitments. You can do either of these by sending our service department an e-mail, even a  simple phone call will do.

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