Brake Fluids and ABS
by Pat Goss
No, this is not a luscious drink. Actually what this is, is Dot 5 brake fluid that we have put into a blender to simulate what goes on in a car with ABS brakes and Dot 5 silicone fluid. You see that foam on the top? Well if that was in your ABS system your pedal would sink closer to the floor. Your stopping distance would increase and you would be in trouble. Never use Dot 5 fluid in an ABS equipped car.
If you look at an ABS system all of this looks pretty complicated but really it’s not all that bad. Here are some of the basics. This is a wheel speed sensor. It’s mounted back in by the axle of the vehicle and it rides very close to this tone ring on the end of the axle. Now you see, each one of those teeth on the tone ring as the axle rotates it send a signal through the sensor back to the ABS computer. If one of the wheels is turning noticeably slower than the rest of them while the brakes are applied the computer senses that and it reduces the braking pressure on the slowest turning wheel to keep it from locking up.
Alright now, what are some of the things that can go wrong with this system? Well many of them are very, very simple. Go off road, get into some mud and you may find these tone rings get clogged with crud. So you clean them out. Another thing that happens lots of times is metal fillings from worn out brakes or from doing brake work they collect in here, you have an ABS light. And the only thing that is really necessary just clean the tone rings. So don’t overlook that. Also, you say that, you know brake fluid you can look at it and you can tell that it’s good or bad. Well yea you could look at it and if it’s really discolored or nasty looking its bad and the brake system needs to be flushed. But just because it looks good doesn’t mean it is good.
If you look at these two jars they look pretty much the same, you’d be hard pressed to tell if there was a problem. Yet this jar (left) is 50% water and 50% brake fluid. So rule is, flush the brake system every two years, every six months use a test strip to check the condition of the fluid and if it fails before the two years, flush the brake system. Now by doing this you’ll drive a safer car and you will prevent a lot of the moister related damage to the hydraulic system in your car and that’s going to save you money.
If you have a question or comment, write to me.
The address is MotorWeek, Owings Mills, MD, 21117.