brake fluid warning lights information

Pat Marron Jr. & Dave Eastman

Pat from Tune Tech Downtown and Dave Eastman of the Auto Shop Connection

Drivers Guide to Brake Fluid and Brake Warning Lights TTD007

In this episode we’ll continue the series on auto brakes. We will expand on brake fluid contamination and share more information about brake system warning lights.

In the first episode on brakes we covered the importance of adding the correct fluid to your brake system. We discussed the vehicle inspection that each vehicle gets that comes into Tune Tech Downtown in Boise ID.

Pat described how their mechanics measure disc brake pad thickness during the inspection. He shared how important it is to have regular brake checks to avoid wearing the pads down to the metal backing plates.

The cost of doing a brake job can double when rotors and other brake parts are damaged by worn out brake pads. Pat presents a case study of a truck that suffered this type of problem.

In this episode Pat starts us out by revisiting the topic of how important it is to use the correct type of brake fluid. His recommendation is to always check your vehicle owner’s manual before adding anything to the system.

At Tune Tech our mechanics use repair manuals to look up the correct brake fluid for each vehicle.  We always install the type of fluid the manufacture recommends.

brake fluid reservoir

Brake fluid contamination can damage all brake seals and hoses

In the previous episode we talked about brake fluid contamination.

We said in the past older brake fluids were contaminated by moisture. Today the fluids in cars are not harmed by moisture. Now we test for cooper content as a contaminant in the fluid. We use test strips to tell us how much cooper is in the fluid.

Brake fluid has corrosion inhibitors that breakdown over time, which can cause corrosion of internal brake parts. The corrosion pulls cooper from internal parts, which degrades the fluid. If too much cooper is present in the fluid it must be flushed with clean fluid.

Another form of brake system contamination is when someone adds the wrong fluid to your brake system. If your owner’s manual says use only DOT 5 fluid, you should not have DOT 4 or any other type added.

Some fluids are reverse compatible. This means new fluids will work in place of older fluids. If you go to a parts store to buy fluid be cautious about fluids that parts counter people say are compatible with your vehicle. The best practice is to put the type of fluid required by manufacture.

Pat mentioned a case study of a car that had transmission fluid put in the clutch master cylinder. We haven’t talked about clutches, but they use brake fluid and the systems function almost the same as brakes.

In this case a relative added the wrong fluid in the clutch master cylinder. It turned into a very expensive repair because some parts had to be replaced.

Adding the wrong fluid to a brake system may require, at minimum, a flush. It depends on what the contaminant is and how long it has been in the system. Sometimes it can be fixed with a system flush. But, it’s highly unlikely that any shop would do a flush to fix this problem.

Brake system operation is a safety item so the most likely fix will be to replace all components that the contaminated fluid contacted. That could include disc brake calipers, wheel cylinders, hoses and master cylinders. Then a decision will have to be made about any hydraulic Anti-lock brake (ABS) components that might need to be replaced.

The liability for a shop is so high that they would probably not take a chance on just flushing. Most shops will require component replacement to protect themselves and their customer.

Brake Warning Lights

Automotive Brake Warning Lights

In the previous episode we talked about brake warning lights. Here is a little more information about brake warning lights for hydraulic brakes, Anti-lock brakes (ABS) and Traction Control (TC) systems. In the next episode on brakes, part 3 of this series, we will present more information about Anti-lock brakes and Traction Control.

There are 3 warning lights that can come on. A Red Brake light, Anti-lock and Traction Control lights. Some vehicles may turn on a dash message rather than a warning light, or do both. Here are the lights with a brief description:

  • Red light – indicates when there is a hydraulic brake fluid failure in the base-brake system, or Anti-lock brake system. It also turns on when the park brake is set
  • Orange Anti-lock light usually relates to an electrical or electronic failure in the ABS system
  • Orange Traction Control light can come on due to problems in any part of the brake system because TC usually uses the brake system to control slippage

One last note about warning lights is that one or more lights could be on depending on the problem. The systems share components so if one part fails the diagnostic system could turn on multiple lights or warning messages on the dash.

antilock brakes system

What happens when a Red Brake, ABS or TC light is on?

The last point to make about warning lights is that when an ABS or TC light is on that system is not working. The light comes on because a computer has seen a problem and de-activated the system. The computer is programmed so when a problem occurs, it can’t guarantee the system will work properly, so it shuts the ABS or TC down.

If your base brakes are ok, and there is just an electrical or electronic problem you will still have base brakes. Remember to always follow your owner’s manual anytime a warning light is on.

Conclusion about brake fluids and brake warning lights:

Always check your vehicle owner’s manual to determine the correct type of brake fluid to add to your brake system.

As we have described in this episode the cost of repairing a contaminated brake system can be very costly. A shop like Tune Tech Downtown cannot see inside hydraulic brake components to determine if they are bad. Contaminated parts will be replaced in almost all cases.

We reviewed the three brake warning lights you see most often on cars and trucks. Then we gave you some information about why they come on and what the result will be with the light on.

We hope you found this information on the Auto Care Podcast helpful. If so please go to your Apple Podcasts or Google Podcasts App and give us an honest review about the information we shared. If you listened on a computer we would appreciate a Google review as feedback to let us know how we are doing.

What you’ll learn from this episode on brake fluid and brake warning lights:

  • Always check your vehicle owner’s manual for the right type of brake fluid to add
  • Contaminated brake fluid may require brake component replacement
  • Brake fluid additives break down and require a flush to replace the old fluid
  • There are three brake related warning lights – Brake, Anti-lock and Traction Control
  • What happens when a brake warning light shows on the dash
  • A case study of a vehicle that had the wrong type of fluid added

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