I bled my brake system about three or four months ago (after years of neglect, I suspect) after doing the rear brakes, and when I was working on the front brakes I noticed that the new brake fluid already looks inky and dark. It doesn't look as bad as the old stuff, but it does look noticably dark green and inky. Is this a problem in my lines that I need to address, or will another bleeding take care of it? Or is it something that's just normal and I haven't ever noticed it because I haven't opened up my brake lines so soon after bleeding them before?

Hi

I've occasionally bled brakes because they had a spongy feel. With someone pressing on the brake pedal (only ½ way - see below), I'd do a wheel at a time till I had a gob of air come out. Then I'd tighten the nipple and see if the pedal had improved. Sometimes you get the right wheel or circuit straight away, and the pedal comes up, so why waste more fluid and time, unless the fluid is old anyway.

Changing is more thorough. You keep going till it's clean, and if it's history is doubtful, you may have to do it a couple of times, a few weeks apart.

But, I've always only pumped the pedal as far as it's normal travel though, at least after I ruined a master cylinder (on a Toyota). The master cylinder has the cups running up and down the bore, day in, day out for years. The rubber cups get a bit harder in time, and the bore wears ever so little, but enough to leave a lip at the bottom of it's normal travel. So when you pump the brakes with the nipple undone, the rubber cup runs over the sharp lip several dozen times. You get the brakes seemingly OK, new fluid etc. A week later you're sitting at a traffic light with your foot on the brake, and wonder why the pedal starts to sink a little. A month later, it's got worse - so bad that it's a bit scary. You can sink the pedal to the metal when bleeding if the cylinder is relatively new, though.


Alan (Australia)

Hi

Did you bleed it (to get out air bubbles) or change it (to get rid of the old fluid)?

If you changed it, did you replace all of it? I'd suspect some of the old fluid will remain (in the calipers, master cylinder etc), and over a period will mix with the new, making it look dirty. If the old was quite dirty looking, I'd be doing it again now, and check again in a few months.

I assume they are working OK.

Alan

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Isn't this one and the same? I bled the system to get out the air bubbles, and in the process changed all of the fluid.

You may have some rubber deterrioration in the seals on the master cyl or the calipers .

If the brakes are still functioning properly with no questionable behaviour, try flushing the brake fluid again first tosee if it is just old residue, then check again after a while to see if more junk shows.

If it does, you have something about to go.
--
-------Robert, '93 940t, '90 240 wagon, '84 240 diesel (she's sick) , '80 245 diesel

the fluid absorbs water, and corrosion results. in the bottom of the low spots, like in those expensive multi-piston calipers. every so often, I REPLACE the fluid. note the all caps.

use a turkey baser to suck out all reservoir fluid. rinse with a little new fluid, and suck that out as waste, too. then bleed the brakes, in the prescribed order not just to get the air out, BUT UNTIL NEW, CLEAN FLUID COMES OUT OF EACH AND EVERY PORT. then, in an unusual manner, open the bleed port very much and hammer the pedal very quickly and hard in an attempt to develop enough flow to clean the bottom of slave (you see, the bleed port is at the top of each slave cylinder, and the crap you want to remove is at the bottom--but you don't want to take it apart just to get this grunge). do the best you can, and move on to the next prescribed point. After that unusual procedure, you may want to do one more normal air removal bleed---but I have never had air suck back in like the old-timers warn you against.

When I was young and had energy, I would do this every 3 or so years. now, I live in colorado (no moisture) and am old and tired (36), so I let it go.

properly dispose of the chlorinated oil waste. You may consider buying the larger containers. a pint is not enough