Get a grip......... when was the last time you ACTUALLY had your brake fluid changed? The answer, for almost everyone, is never. Maybe, just maybe, if you had major work done to the brake system, somebody bled the brakes.
Is it a good idea at some point? Surely...... but does anyone do it? Maybe someone with a performance car that is bent on upgrading, but all the run of the mill rides I've ever had, not.
How many master cylinders have you replaced over the eons? It seems to be a common failure with older cars. Do they have to be replaced because of corrosion?
According to the information linked to from this thread, the corrosion of the copper lines is the culprit, in turn corroding the iron once there's enough copper in solution.
I had to replace cast iron calipers twice on my used Hondas because previous owners had never changed their brake fluid, the corrosion pitted the bores too deep for a hone job. I'm sure all that moisture and sediment floating around is great for the ABS valve body.
Sure, if you don't plan to keep the car for 10 years and don't care about the future owner it's unlikely you will have problems in the next 8 years.
Get a grip......... when was the last time you ACTUALLY had your brake fluid changed? The answer, for almost everyone, is never. Maybe, just maybe, if you had major work done to the brake system, somebody bled the brakes.
To answer your question directly, 3 months ago I changed the brake fluid (and manual clutch fluid) in my '79 Mercedes 240D. Since owning the car, I have changed the brake fluid 5 times. On my '96 Mercedes SL600, the dealer changed the brake fluid 4 months ago; the 3rd change since I've owned the car. On our '02 Mercedes ML430, it was changed last year, since we purchased the car ‘pre-owned’ last year. I have records to substantiate these maintenance activities. Yes, I do change my brake fluid.
Clearly, you have never changed your brake fluid or you’ve never owned a car long enough to desire it. That is your prerogative. If you had changed it - even occasionally - you would notice a marked improvement in braking feel. The old fluid that comes out is usually very dark amber in color with a slight odor. As the fresh fluid replaces the old, the clarity returns and the odor changes.
As mentioned by others, the longevity of hydraulic cylinders is positively affected. Hydraulic cylinders are generally made of cast steel, machined to tolerance. Water – in any appreciable amount – causes rust within them, causing the rubber seals to wear. On my ’79 Mercedes, the master cylinder, all 4 wheel cylinders and the clutch cylinder are original; they’ve never been changed. The car has over 290,000 miles on it, is 30 years old, and I personally know the previous owner (who took care of the motorcar).
Whether you change your brake fluid or not is your call. But do not pooh-pooh an established idea simply because it doesn’t fit your frame of thought. I think I’m in good company on this topic. Peace.
As the brake system heats up, brake fluids with low boiling points begin to vaporize. The brake pedal must travel further to apply the same amount of force on the brakes, causing a spongy feeling. If enough of the brake fluid vaporizes, brake system failure may occur. Brake fluid boiling points are measured on two separate scales:
Dry equilibrium reflux boiling point (ERBP) - the boiling point of new, freshly-opened, unused fluid.
Wet ERBP - the boiling point of a brake fluid after it has absorbed three percent water.
The minimum dry ERBP for DOT 4 brake fluid is 230°C (446°F), while the minimum wet ERBP is 155°C (311°F). Their higher boiling points make DOT 4 fluids appropriate for high-performance cars and motorcycles and for vehicles used for towing or in mountainous regions.
Brake fluids fail 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.
The end result is even though DOT 3 fluid is "rated" at greater than 401oF, in the typical 3 to 4 year old car with 3 to 4% moisture content, it could boil under 300oF. And if it has got more than 4% moisture, you may as well be running straight water!
...since the smart comes with dot 4 which has a very good LMA.(low moisture activity) is up to you if you want a squishy pedal or a brake system that will work well an inch away from the 500* rotors....
Water – in any appreciable amount – causes rust within them
The great thing I learned from this thread is that it's the copper ions (from typically copper brake lines) that causes the pitting in the iron components. Not water!
Not trying to get off-topic or slam the above contributor, but I do change my oil - synthetic or not - every 4-5K miles. Why? Because while the Mobil One synthetic oil will stand up to 10,000 miles of use, the ridiculously puny oil filter will not. Once the oil filter starts to clog and the bypass opens, the world's best oil will not stop the crud from being recirculated in the engine. I really believe that engine oil - especially in today's high-temperature running engines - cannot be changed often enough; especially in the Smart/Mitsubishi 3-cylinder, 1-liter powerplant. Maybe I'm guilty of being an 'old school' kind of guy, but the cost of 10 extra oil changes over a 100,000 mile period is good investment against engine wear.
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