When’s the last time you checked your brake fluid!
A couple of months ago before heading up to Virginia International Raceway for a romp around the track with some other Corvette enthusiasts, I did the obligatory under the hood inspection, especially fluids. When checking the brake fluid, I noticed that it was especially dirty with some sediment in the bottom of the reservoir. I referred to the owner’s manual and surprisingly there was no reference to break fluid maintenance.
I contacted my Corvette guru at the local dealership and asked him about brake fluid as a maintenance item and he told me it was Chevy’s recommendation that brake fluid should be changed every three years or 40,000 miles in the C5 and C6 Corvettes. With that info in mind, I contacted a buddy that is an Amsoil distributor and ordered some AMSOIL Series 500 DOT 3 High-Performance Synthetic Brake Fluid. It took about an hour and fifteen minutes to completely evacuate, flush, refill and bleed the hydraulic system. First test drive, I could tell a difference as soon as I applied a heavy break.
Here’s a little tutorial on the hydraulic brake system. There’s a lot happening between putting your foot on the brake pedal and the brake pads. In a brake system, the fluid’s pressure is multiplied by the master cylinder and typically can reach more than 1,000 PSI in the lines. (Two things to be aware of here, pressure and heat) Like any other hydraulic fluid, brake fluid must be non-compressible at the expected pressures to cause force from one end of the system to the other while concurrently lubricating the pistons and rubber parts as they move through their bores. If the brake fluid were to become contaminated allowing some compression, braking power would be compromised.
Brake fluid is subjected to very high temperatures, especially in the wheel cylinders of disk brake calipers. It must have a high boiling point to avoid vaporizing in the lines. This vaporization is a serious problem because vapor is compressible and counteracts hydraulic fluid transfer of braking force. Brake fluid fails either because they boil or because they cease to provide adequate lubrication and corrosion protection. Both reasons for failure are the result of contamination, usually by water or petroleum products.
DOT 3 and DOT 4 polyglycol ether-based brake fluids are “hygroscopic,” which means they absorb water easily and hold it in suspension, similar to antifreeze. In most climates, moisture seeps into the brake system continuously through the various seals and microscopic pores of the flexible brake lines. This seepage can accelerate as your car ages and there’s almost no limit to how much water the fluid can absorb. By the time brake fluid has been in the system for three years, it can easily reach its wet boiling point. Because this happens gradually, most drivers won’t discover the reduced braking ability until it’s too late.
So, if you have a 2009 or older C6, consider changing your brake fluid. It’s an inexpensive maintenance item. Approximately half of all cars and light trucks in the U.S. over 10 years old have never had the brake fluid changed. Think about that as you are coming to a stop and looking in your rear view mirror!
By: James J. Prunty