3-Series (E21, E30)Chat relating to the BMW 3-Series from 1975-1983 and 1984-1991 line. Specific models: BMW 315, BMW 316, BMW 318, BMW 318i, BMW 320/4, BMW 320i, BMW 320/6, BMW 323i, BMW 320i. E30 Family models include: BMW 325e, BMW 325i, BMW 325is, BMW 325ix.
Well, I just noticed something very frightening today.
I popped my hood to check my fluids. I checked the brake resevoir (which I haven't checked in awhile) and I noticed that there's some black soot at the bottom of the filter cup. I took out the filter cup and removed (dumped out) the black soot easily.
So, does this mean that the square-cut seal is rotting in one of my calipers? Does it mean the cups in my B.M.C. are going out? I always use Dot 4 and nothing less (that's what the cap says to use!).
Yeah, go ahead and flush the whole system out with new fluid. One of the fastest ways to do this that I have found is to gravity bleed first. This entails taking a large bottle of cheap brake fluid and opening it and turning it upside down into the top of your resiviour so that it will fill it as you bleed. Then go around and crack your bleeders open and let the old fluid flow out for a couple of hours. All the while making sure to keep the resiviour full. This process will let any sediment that has collected in the caliper bowls seep out without agitating it by pumping the pedal and getting it all swirled up in there. Once you let it bleed out for a while and you see all new fluid in the resiviour, go ahead and start using your good fluid "ATE" and close off all but the furthest from the master cylinder and start bleeding it manually and move around the system from furthest to nearest the master. I'm not sure about the ABS on these cars and if it needs to have a special proceedure done with it or not, ask Starmavin.
That "soot" is just a sign of wear, it's from the rubber cups in the master cyl, a fine layer is actually harmless unless your fluid is really nasty. If your fluid is dark, coffee like colored, then flush your system. There isn't anything special to do with the ABS on these cars.
To flush it, what I do is I'll take an empty oil bottle, spray it clean with brake parts cleaner (best stuff in the world) then take a 2 foot clear line, one that fits the bleeder tight (found at lowes or hardware stores), cut a hole in the lid of the oil bottle then push the vacuum line all the way in to the bottom, "prime" the bottom of the bottle with about 1/2 inch of brake fluid, stand it up on the ground push the hose on the bleeder, crack it loose then just pump it with top to floor pumps until it's clear, just remember to refill the master cyl after the 4th or 5th pump and to close the bleeder before you pull off the line, then repeat at all 4 wheels.
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