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How dirty should brake fluid be before changing it?

S

skeelo58

New member
I bled my brake system on my car this weekend to get all of the old stuff out. It was fairly dirty, I would say a little darker than a cup of tea? To the best of my knowledge, it had never been bled out before. After changing it out it kinda felt like my brakes were a little more responsive. Is that just a placebo effect? Or was the dirty brake fluid causing some problems?
 


old fluid needs to be changed, if its a 10 year old car, and never had brake fluid changed, fully, you will feel a difference for the better.
 
Brake fluid is in a closed environment. Technically it shouldn't get dirty. It does though and it's performance is also based on it being reasonable.

I flush the fluid on my brakes when I get a car. Typically older cars. So ..I'd say anything ~5 years is worth doing.
 
BillBoost37 said:
Brake fluid is in a closed environment. Technically it shouldn't get dirty. It does though and it's performance is also based on it being reasonable.

I flush the fluid on my brakes when I get a car. Typically older cars. So ..I'd say anything ~5 years is worth doing.
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ive been told its burnt, thats why it turns so dark. (when well used) heat from the calipers breaks it down.
 
That and the rubber lines break down and add in contaminents, and any rust that forms in the steel lines will also leach into it, as you know brake fluid is hydroscopic which I would think cause the lines to rust a bit internally.
 
Brake fluid is corrosive. Fluid is carried through steel lines .The color of the fluid is a result of corrosion between metal and brake fluid.

FordMan77 said:
That and the rubber lines break down and add in contaminents, and any rust that forms in the steel lines will also leach into it, as you know brake fluid is hydroscopic which I would think cause the lines to rust a bit internally.
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Proper way is to check with a device that measures water content percentage.

I think its 2 or 3% it should be changed at.

If you can't get your hands on one, every two years.

Once container is opened, use it and dispose of the rest. Its now garbage.
 
Also, most of the time, when flushing a system, "Gravity Bleeding" works well if you dont have a second hand. Put the car up on stands, and pull all 4 wheels. Put some sort of a catch basin under each brake (ask your wife/gf if you can use her tupperware...lol) and open the bleeder screw on all 4 wheels about 2 or 3 turns. Let all 4 bleed at the same time. Your going to want to stand by the resivoir and let it get down to the low mark before topping off the fluid. Just be sure not to let it go dry. Repeat topping off the resivoir 2 or 3 times, to ensure at least 90% of the old fluid gets flushed out. Close up the bleeders, hose everything down with brake clean, top off the resivoir once more, and close everything up.


This is how we did it at the Toyota/Lexus dealership I worked at. As long as no one hits the brakes and you don't let the res go empty, you will not introduce any air into the system.


Jay
 
Gravity bleeding is indeed a wonderful method. I have had do many tranmsission jobs on my Stealth without a second set of hands so I have used gravity bleeding to bleed my slave cylinder on many occassions.
 
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