[diesel_mercedes] Re : Periodic Brake Fluid Replacement

 


Not all Mercedes have ABS , it makes proper bleeding out more tricky .
 
A pressure bleeder should be used to bleed out ABS equipped cars , they're available for about $50 new , less used .
 
Brake fluid should be changed every two years or whenever it's black or brown .
 
Doing this isn't expen$ive , just time consuming but the up side is : you'l never have leaky / sicky brake calipers or master cylinder if you do this .
 
The car needs to be supported well off the ground using saftey stands or tree stumps , NOT CINDER BLOCKS as they'll shatter without warning & drop the THREE TON Automobile on you , game over .
 
You'll need a clean glass pop bottle and some vacuum hose that fits snugly over the  bleeder screw on the caliper , a box end wrench the same size as the bleeder screw ~ DO NOT attempt to use open end wrenches , pliers , vise grips etc. ! .
 
I like to use a cheapo plastic syringe or turkey baster , battery filler bulb etc. to suck all the old brake fluid out of the master cylinder first , be aware that brake fluid instanly ruins the paint so be careful .
 
NOTE : brake fluid is damaging to other fluids so I have dedicated brake fluid tools , they're clearly marked with a permanent Magic Marker .
 
Fill the master cylinder with DOT 4 (disc brake rated) brake fluid , you'll need at least a quart so have enough on hand before beginning , connect the vacum hose to the right rear bleeder screw and slip the box wrench on , dunk the open end of the hose into the empty pop bottle , make sure it's long enough to reach the bottom .
 
Depress the brake pedal and have your assistant hold it down with the toes of their foot , open the bleeder screw 1/4 turn or so , just enough so air bubbles & brake fluid come out , your assistant will tell you when the pedal hits the floor & stops moving , close the screw & have them release the brake pedal , wait a moment then have them slowly depress & release the pedal several times , finishing by holding it down , open the screw again , now you should get a stream of nasty black brake fluid with tiny chunks in it , repeat this until each opening of the screw gives you a stream of clear fluid with no bubbles in it , it'll  be *very* noticable when the clean fluid begins squirting into the nasty dirty fluid .
 
Once you have this stream , clear & no bubbles , close the screw , release the brake pedal and go top up the master cylinder with more fresh fluid ,  move the hose , bottle & box wrench to the left rear bleeder screw and repeat , then do the right front and finally , the left front .
 
Be aware the brake pedal may feel low until you finish the left front caliper .
 
All done ? clean fluid in the master cylinder's resivoir ? good ~ now take it for a test drive , if the pedal still seems low or mushy , you can bleed it more (remember I said at least one quart ? I always buy two) or try propping the brake pedal down overnight as this helps remove those last few tiny bubbles .
 
If you get your hands on a pressure bleeder , remember to not use more than 3 # MAX. and just bleed each caliper as described before , no helper needed , just remember to re fill the master cylinder & re pump up the # 3 each time a caliper is done .
 
If you have a hard to open bleeder screw , get your smallest , lightest hammer and *smack* the open end of the bleeder screw dead on , not at any angle , this shock will make it easy to open . if it snaps off , relax the caliper wasn't any good anyways , go buy a rebuilt one at your local discount FLAPS , be sure to match the brand of caliper as there are Girling , Bendix , ATE and other manufactrers .
 
It is permissable to replace just one caliper , I always replace them in axle sets , that is , pairs so the brakes will have an even pull .
 
You MUST NOT use any sort of oil , penetrant , to clean or de rust the brakes ! only brake fluid , alcohol or brake cleaner may be allowed to touch the hydraulic system , your LIFE depends on this .
 
I hope this helps .
 
-Nate
        Nate R.  wrote:

 


We need to ask the other Nate about when to change brake fluid.I need to do my S , but don't know if special procedure for ABS brakes.



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