Brake Fluid change intervals - What to believe ???

Several online sources (auto parts store , garages ) have recommended flushing and replacing brake fluid at intervals of 24 months / 24000 miles citing fluid
contamination andmoisture retention as primary reasons....and to purge any air as secondary reasons, unless the system has been opened.
I also looked at the Owners manual for two different GM vehicles, a Chiltons manual and a factory service guide. None of these specified periodic brake system flushing although the service guide gave some very general guidelines.
However, not a whole lot of shops advertise the need for this procedure... If you take your car into a Jiffy Lube (just for example), they will replace oil, filters, belts, transmission fluid, but never say a word about brake fluid. If it was that necessary and part of a recommended service program, it seems to me that a lot more tune and lube places would be advertising this service.
So what is the truth here ??? Do mechanics and engineers see a need for regular, planned brake fluid changes ?? Is this marketing hype?? Is the difference somewhere in the middle ??
Appreciate your thoughts and wisdom on this matter !!
Thanks in advance !!
Peter
ps.... raybestos has a brake system learning center at http://www.raybestos.com/OnLineTraining/abs-177.htm
It also has some training programs.... I could only find a backdoor link at http://www.raybestos.com/OnLineTraining/abs-177.htm but this might help someone.
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24mos/24Kmi seems reasonable. I've always gone by what the fluid in the master cylinder looks like. If not clear, I do a gravity flush with new fluid. Brake fluid is not expensive given the small amount in the system. Safety is the primary concern and fresh fluid is cheap insurance.
Dave S(Texas)
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I've also read that regular flushing will extend the life of some very expensive anti-lock components. I've been doing this to my cars and trucks since the "70's" and I've never had to repair or replace a wheel cylinder or caliper, and I usually keep a vehicle around ten years.
Al

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When we service fleet vehicles we did so at two years or 50K, WOF. Problems stems from moisture, not particulate, contamination
mike

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I've never done a "change" per se, but have bled brake lines and added new fluid. Don't know if changing helps, but certainly can't hurt.
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Peter wrote:

I've never seen a change interval specified for non-ABS cars, except for European cars, one which recommended replacing it every two years, with no mileage requirement. OTOH Ford said that its red DOT 3 brake fluid was permanent but didn't say if it had special additives to prevent corrosion better than other DOT 3 fluid did. I'm no expert, but if I had ABS or stability control, I'd change the fluid every 1-2 years because some of the special components for those systems can cost $1,000+. I would also not let a quick lube place change the fluid because they might screw up the brakes, especially ABS, which can require special procedures for bleeding the brakes or even just checking the brake fluid level. For example, one of those places topped off the fluid in my friend's car, and later a lot of fluid leaked out because they were supposed to pump the pedal 50 times to empty the accumulator and prevent a false low fluid level reading. Brake fluid dissolves paint.
I live in Phoenix, a fairly dry climate, but even here the fluid in the plastic reservior turns dark in about six months, and I've read that half of the moisture gets into the fluid through the rubber brake lines.
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Peter wrote:

For no apparently good reason some auto makers suggest changing the brake fluid every two years while others claim it is good for life. I know that Volvo, VW and Honda for example do call for periodic changes.
Personally, I do it on all our vehicles as it is inexpensive and makes plenty of sense.
John
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Try DOT #5 next time, and eliminate the need for further changes, if you keep your new vehicles longer than the average three of four years, WBMA
mike hunt

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Mike Hunter wrote:

Even if the car has ABS?
For DOT 3, are there any significant advantages of synthetic vs. regular?
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Silhouette and a 2002 Monte Carlo (ABS)
Also, it seems like DOT 3 - 4 and DOT 5 are incompatible with each other, requiring a complete system flush when switching from one to the other. This is just presented as general information.
Peter
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Peter wrote:

They are imcompatible with one another, and also there's some concern about DOT 5 cavitating in an ABS control unit which is probably the reason for the warnings. Supposedly there's a DOT 5.1 which is compatible with DOT 3/4 (i.e. not silicone based) but meets the performance specs of DOT 5 but I have not tried it so I can't give an official recommendation.
The official word from most of the mfgrs. is that brake fluid changes are not necessary, that the brake system if left sealed will not absorb enough moisture over its lifetime to cause corrosion, and in fact changing the brake fluid may cause more harm than good because of the possibility of introducing dirt and contaminants into the ABS HCU. However, the caveat is that most of them consider the "lifetime" to be only ten years. So you pays your money and you takes your pick. I personally would go ahead and flush; however, be smart about it - keep everything scrupulously clean when you do so; might even be a good idea to clean out the reservoir before beginning (use turkey baster to empty.) When replacing pads, open the bleeder screw as you push the pads back in as you do not want to "back flush" any goo into the HCU. However, if you plan on wearing the vehicle completely out within ten years, it's probably a waste of time, even though it feels like a lack of proper maintenance.
nate
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This is painting the manufacturers with a bit of a broad brush.
Moisture doesnt penetrate rubber hoses and get into the brake fluid. But even with the better designed brake fluid tanks, moisture may eventually contaminate the system.
With a lot of cars, brakes will be changed every few years and we would hope that the line would be flushed and bled.
I have a Teves system in my Reatta, and we are warned to flush the system every two years. It is preventative maintenance. If you abuse a Teves system and get corrosion, you are looking at $1000-$2000 to get it back in shape. A person would have to be a fool to neglect maintenance in such a system.
How many ordinary braking systems have I rebuilt to find the cylinders pitted and full of 'mud'? Lots of them. If changing fluid helps prevent brake failure, and improves safety, it costs little enough.
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hls wrote:

AFAIK this is current recommendations for GM, Ford, and Chrysler, so...

I *agree* with you... I'm just explaining the reasons why mfgrs. do not recommend rfluid changes.
nate
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Nate Nagel wrote:

Hmmm, interesting. Frankly I don't buy the argument these mfgs. make at all. Most systems are vented in some manner to provide for expansion and contraction of the volume in the reservoir. I have used bi-annual fluid changes to maintain our cars and enjoy very long lived master cylinders, calipers, etc. as a result.
John
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Brake systems are closed, not vented. The air space in the M/C cap takes care of any expansion or contraction.
I have used bi-annual

Sounds like a plan...
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every 3 or 4 yrs. Have never had a brake problem related to lack of fluid changing. My current car is in it's 11th year, I've keept a previous car 10 years, a few others for 6 to 8 years. Our climate has a wide temperature range and is damp most of the year.
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