Is neccesary to replace the brake fluid at 20k? - Page 11 - Smart Car Forums
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post #101 of 107 (permalink) Old 05-18-2010, 08:54 PM
 
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Originally Posted by Godfather View Post
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.
I read through this entire thread. I have to say, I used to buy into the "you must change your brake fluid every 2 years" mantra. Just like I used to buy into the "change your oil every 3,000 miles" song as well. The fact of the matter is, I believe these are things that used to be applicable in the "olden" days, but simply are leftover "truisms" that no longer apply to modern equipment.

Just like modern engines have better tolerances, run cleaner, etc., they can go much longer between oil changes. 5,000 seems to be the minimum manufacturer recommendation, with 7,500 and 10,000 much more common. As far as brake systems go, they system is sealed and air tight. If it wasn't, you'd get air in your lines and you'd have problems (and fluid leaks). So, where is this moisture going to come from? Even if the reservoir cap isn't totally air-tight (which would be a faulty cap in any modern equipment) how much air could possibly get through? And that air would have to carry water molecules with it. And since the fluid isn't circulating, what's exposed?

Even if the fluid darkens, that doesn't mean it isn't effective. People used to check your oil by looking at the color. With modern detergents in oils, your oil can look "dirty" in 50 miles. Does dark brake fluid mean it's not effective or that it's just changed color?

The thing that sealed the deal for me was when I was looking for some online info for brake service on my other vehicle (2004 Ford F-150). There was practically the very same discussion going on. There were people claiming to have never changed their fluid and everything is working fine…well past 100K miles. One person went so far as to claim that there was no recommended service interval for brake fluid changes!

Well, that was it--I went straight to the maintenance schedule to prove this nutcase wrong. Surprise, surprise on me. There is no recommended brake fluid change interval on that vehicle. I checked every service in the entire book.

So that leaves me (and probably some of you) with a burning question: how can it be necessary to change brake fluid in one vehicle every two years or 20,000 (24,000?) miles yet not need to change it at all in another vehicle? By now, some of you might be thinking the fluid in my truck is DOT 5 so it isn't water-absorbing (hygroscopic for those of you who prefer the big words). Nope, it's DOT 3, the lowliest of all brake fluids.

So, I pose that question back to the group: how can it be possible that it's so important to change so often in one vehicle, but not ever necessary (sans replacing parts that would necessitate a change) in another?

For what it's worth, in all the vehicles I've ever owned, I never had a master cylinder failure, and I only replaced calipers once on an '82 Volvo I had. I did replace the fluid once in an Audi back when I was younger and thought that if I religiously replaced all fluids the vehicle would last longer. Well, I don't know if that's true, except I never have since and I've owned all of my vehicles well past the 100K mark.
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post #102 of 107 (permalink) Old 05-18-2010, 09:50 PM
 
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Moisture getting in the brake fluid will lower its boiling temperature and that is what manufacturers are concerned about. Moisture can get into the system through the atmospheric vent in the master cylinder cover or cap if the rubber diaphragm is compromised. Moisture can also permeate the rubber brake hoses which can be accellerated if the hoses are beginning to crack and age. There are several ways to check for excessive moisture in the brake fluid. The easiest way is to purchase litmus paper made specifically for this purpose. It is available at your local autoparts store. The other factor is not to open the master cylinder cover to check brake fluid level in the reservoir. This lets in moisture. I question how clean the fluid would be at your local SC or independant service facility. It they leave the can open or sitting on the bench, it will absorb moisture. I think that this service is probably not that necessary if you keep the reservoir closed and the system is kept sealed. If the fluid turns to a darker color, dirt and particles from the flexible hoses is starting to flake off. You must also remember that quite a bit of heat is absorbed by the brake fluid especially from the caliper piston. A lot depends on usage and climate. Low humidity=less moisture. High humidity plus severe usage that generates a lot of heat and the fluid will begin to detiorate. The use of a vacuum or pressure brake bleeder makes changing fluid a lot easier. Very minute amounts of air can also be drawn into the system through the hoses and past the caliper seals and changing the fluid will also result in a firmer brake pedal if the system is properly purged and bled. This should be done at the bleeder screws on the front calipers and the rear wheel cylinders. There is a recommended sequence for performing this task. A service manual would be nice with a hydraulic system diagram. Bleeding may also require the use of a scan tool to activate the ABS unit so that the old fluid can be purged and fresh fluid introduced into the ABS. :eek:
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post #103 of 107 (permalink) Old 05-19-2010, 07:36 AM
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+1 for timhood. Leave the cap on, don't mess with the fluid, have a nice day. The oldest smarts in the USA are coming up on 2.5 years - hardly time for the brake hoses, seals, etc. to deteriorate. Just drive it.
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post #104 of 107 (permalink) Old 05-19-2010, 03:00 PM
 
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Originally Posted by jwight View Post
+1 for timhood. Leave the cap on, don't mess with the fluid, have a nice day. The oldest smarts in the USA are coming up on 2.5 years - hardly time for the brake hoses, seals, etc. to deteriorate. Just drive it.
Thanks. And I should mention that I have one of those "oldest" smarts. Feb '08 delivery. If I run into an issue with the brakes (leaks, blown master cylinder, deteriorated performance, fluid boiling, whatever) I promise I will personally post a very public "mea culpa" here. Of course, since I'm only a moderate driver, it will very definitely have to be an issue as the result of time, so it will be years before you could expect to hear anything.

If I begin to notice any diminished performance not attributable to normal wear of pads/rotors, I may entertain having the fluid checked for personal peace of mind and possibly a public "I told you so", but again, I don't expect that to happen for at least a couple more years.
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post #105 of 107 (permalink) Old 08-22-2019, 04:45 PM
 
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In so many words - NO. This is not 1950 and your not using junk DOT 3 fluid either. The system is air tight and closed.
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post #106 of 107 (permalink) Old 08-22-2019, 08:23 PM
 
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9 Year Old Dead Thread, brought back to life. Why??
Trying to keep the forum alive??
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post #107 of 107 (permalink) Old 08-23-2019, 06:25 AM
 
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Originally Posted by beakyboy View Post
In so many words - NO. This is not 1950 and your not using junk DOT 3 fluid either. The system is air tight and closed.
And, system is not air tight, it is vented and susceptible to moisture over the years.
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