Brake line flush helps reduce corrosion

BY Jim KerrBackyard Mechanic. Nov 10 04:00 am

Question: I have a 2012 Hyundai Santa Fe. The dealer is recommending a brake line flush. I have never heard of this before. I’ve never had one recommended by Honda for my 2004 Accord. Is this required/necessary maintenance? If so, can you explain why?

Answer: The maintenance charts in almost all vehicle owner’s manuals do not have any mention of brake fluid flushing. Instead, the brake fluid is typically changed when brake pads and shoes are changed or part of the brake hydraulic system is replaced due to a failure. At that time, the technician will “bleed” the brakes to remove air and old fluid in the brake system and top up the master cylinder with new fluid.

For vehicles that are driven a lot and have their brake parts changed every couple of years, this may be enough. But for most of us, it is better to have the brake fluid “flushed,” or changed, every couple years. One of the primary reasons is to reduce corrosion in the brake system. Brake fluid absorbs moisture from the air. Moisture can get in from around seals in the brake system over time, and this moisture will mix with the brake fluid and start to corrode metal parts in the system.

Some parts are very expensive to replace, such as antilock brake units and traction-control units. Flushing the brake fluid — and getting rid of the moisture, — will help protect these units from corrosion and reduce the necessity of replacement.

Corrosion can also be caused by copper migration from the steel brake lines into the brake fluid. This occurs over time, even when the vehicle is sitting. There are tests that can be done on the brake fluid to see if the copper levels are too high and the fluid needs replacement, but few repair shops have this equipment. It is easier to just replace the brake fluid on a regular interval, and every two years seems to be about the best compromise.

On another note, any water absorbed in the brake fluid lowers the boiling point of the brake fluid. If the brake fluid boiling point is lowered too much, it may boil if you have to perform emergency braking from higher speeds or slow a heavy load on a downhill grade. Race cars often have the brake fluid changed for every race, just to make sure the brake fluid boiling point is at its maximum because of their severe brake use and heat generation. This usually isn’t a problem for passenger vehicles, but changing the fluid will maximize the boiling point. Be sure to use brake fluid only from a sealed container. An open container will absorb moisture from the air.

Question: Why are Canadian cars not equipped with rear fog lights? In Europe, they are quite common. When fog rolls in, drivers routinely turn on headlights which, of course, turn on tail lights. However, these small lights cannot be seen in daylight. In fog, by the time you see red, you can see the bulk of the vehicle. Recently, I caught up with a foreign car, a SAAB I believe, with built-in fog lights. There was no doubt the car was there and could be seen. Beautiful. I am told they are not illegal, so, why not here?

Answer: Rear fog lights are not illegal in Canada, but they are also not mandatory. There are actually several European cars sold in Canada that have rear fog lights, which are essentially one brake light that stays on while you drive down the road so other drivers can see you easier in poor visibility. Volkswagen and Mercedes-Benz have models with rear fog lights. But not all the models have them, because some are manufactured only for the North American market, and adding the additional controls and wiring for rear fog lights adds cost to the vehicle. It all boils down to money! The cost per vehicle isn’t much, but multiply that by all the vehicles sold and even a couple of dollars per vehicle really starts to add up.

I agree rear fog lights do add to safety, but an alternative in fog conditions would be to use the four way flashers to signal other vehicles of your presence in front of them.