Why Flush Brake Fluid?
Brake fluid is a special oil. It is designed to withstand cold temperatures without thickening as well as very high temperatures without boiling. It is a recommended service for many vehicles and should be flushed about every 30,000 miles.
Brake fluid is an odd duck, it’s like an oil, but it likes water. Yes, brake fluid likes water. That is one of several reasons your vehicle’s brake fluid should be flushed.
Let’s start with the water thing
Brake fluid is hygroscopic; meaning (of a substance) tending to absorb moisture.
If you had a 25 ml cup of brake fluid and added 5ml of water, stir…and poof, the water is gone!
Why is that? Why do we want that to happen?
It’s a fact that moisture makes its way into the braking system (see chart at bottom of page). We don’t want that moisture collect and form into water droplets. Your brake fluid would look something like water and cooking oil, they don’t mix.
We know that brakes get hotter than 212 degrees which means the fluid does too. What happens to water when the temperature goes over 212 degrees? Of course it boils and turns to a gas/air. Air in the brake lines and brake system will make for a very poor, to no braking condition!
All boils down to..
We don’t want water droplets that can become air in the brake system!
Let’s Add Water
Putting this all together makes it easy to understand why brake fluid is designed to prevent the formation of water droplets in the system.
A good quality brake fluid has a boiling point well over 400 degrees but as brake fluid absorbs moisture, the boiling point drops. Brake fluid does more. It has an additive package that helps retain the flexibility of the man-made rubber components in the brake system, prevents corrosion and more.
Check out the charts at the end of this article to find out how only a 3% moisture content can affect the performance of your brake fluid.
A little stir with the magic coffee stirrer..Look no water!
|Over time, brake fluid degrades, just like engine oil and coolant. As it degrades, the protection for the internal parts of your brake system is being lost, which will result in corrosion and premature failure. In addition, with age, brake fluid’s viscosity climbs (it gets thicker).. add in a drop in temperature and matters get worse.|
Slow brake fluid equals poor performance
Cold weather in New Hampshire usually means snow and ice. This happens to be the time that you’ll likely need your anti-lock brakes (ABS). The ABS control has a bunch of little passages with fast moving valves. How do you think old thickened brake fluid is going to work with this system? You can guess, the anti-lock brake system cannot work as designed. What is going to happen to those little valves when the brake fluid can no longer protect them from corrosion?
Also many of today’s vehicles have traction and stability controls that rely on brake fluid. This technology makes a vehicle safer but the technology cannot perform as it should with fluid that moves like molasses going up hill on a cold January day.
Who wants you to change your vehicle’s brake fluid?
Here’s a great example.. Subaru
Subaru, a great car for the north, wants the brake fluid flushed every 30k miles under normal operating conditions. I think the engineers at Subaru know what it takes to keep their Subaru’s operating safely for the long haul. There are many other vehicle manufacturers that want their vehicle’s brake fluid flush as well.
If you don’t follow the manufacturer’s recommended service intervals, at a minimum, have the brake fluid flushed whenever you’re having your brakes serviced.
For many years brake fluid has just been ignored. In today’s vehicles that cannot be done. Good quality brake fluid is required for many of the safety features in your car or truck to work as they should and allow them to last the life of the vehicle.
The Long Life Laugh
Here’s a laugh.. According to GM, their vehicles don’t need their brake fluid flushed. They have long life brake fluid…Don’t bet on it being any better than their long life anti-freeze.
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