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Old 06-10-2001, 02:11 AM
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Join Date: May 1999
Location: Charlotte, NC, USA
Posts: 688
Topping off or bleeding the brake fluid is easy and pushing a little of the old out, but how do you flush the system?
The bleed nipples are always on the top side of the calipers or backing plates but the pressure lines can go in anywhere. So how do you get all the old fluid out along with any accumulated debris that bleeding won't do? Seems as though one would have to remove the caliper, compress the pistons, remove the nipple and do a drain and flush. Then rebleed the whole system over. Anyone know of an easier method or device to help? Curious....

Tobias MB
4 MBs
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Old 06-10-2001, 08:49 AM
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Join Date: May 2000
Posts: 50
Not being a trained automotive technician I can only give you an opinion. I have been replacing my brake fluid on a variety of cars for years. Theoretically the only reason to replace the brake fluid is to eliminate the water from the brake fluid that builds up over time. Brake fluid, being hygroscopic, absorbs water from the air over time. This water will wreck the seals in the calibers and master cylinder and will decrease the boiling point of the brake fluid leading to decreased brake performance. Being a closed system if you have any gunk in the the brake fluid or system you have another problem that replacing the fluid won't handle.

I typically will take the wheel off of the corner of the car that is farthest from the master cylinder and will (with the help of an assistant) bleed the fluid out until the master cylinder is almost empty. I then refill the master cylinder with clean fluid and contine the bleeding operation until clear fluid comes out at the wheel cylinder. I will then do the remaining 3 cylinders until clear fluid runs, top off the master cylinder and I am done for a couple of years. It takes a little time but it is well worth it. Unless you are having other problems with the brakes there should be no need to disassemble any other components.

I understand that they make a one person vacuum bleeder gizmo but I have always just used a jar and a piece of clear tygon tubing. Make sure that you don't get the master cylinder level to low or you could get air into the system and you will be bleeding forever to get it out!!! I know.....

Hope that this helps.
Jim Loseke
1980 450Sl "Black Beauty"
2002 C230 Kompressor "Spicy"
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Old 06-10-2001, 11:05 AM
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Join Date: May 1999
Location: Charlotte, NC, USA
Posts: 688
Understand this but...

that is nothing more than bleeding the brakes. Many manufacturers recommend to flush the brake system every two years. Flushing in my mind is to remove all the old fluid and replacing it. I'd like to replace all my ATE natural fluid with ATE blue but not so easy to get the color that comes from the can out of the bleed nipples
so you KNOW it has been replaced. If the incoming line in the caliper is near the bleed nipple the fluid just does a turnabout and goes out again. I'd like to replace it all in my 190/5.6 before the next track event.

I've made my own bleeder using some 3/16" vinyl tubing, a clear jar with two nipples on top and a AC vacuum pump. This way I just suck it through the bleeder from the master cylinder and make sure no air gets in. Works great for the clutch fluid and other vacuum projects.

Tobias MB
4 MBs
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Old 06-10-2001, 11:47 AM
Shaun McCarren
Posts: n/a
Make sure you don't get any of the fluid on your paint, or you'll have a funny looking paint job.

Shaun McCarren
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Old 06-10-2001, 12:27 PM
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Join Date: Jun 2001
Location: Omaha, NE
Posts: 962
The other issue is what to do if you have ABS. There is a very specific procedure for bleeding the ABS pump which I read a long time ago but have never actually done. I'd be very interested in hearing from someone who has done it successfully.
'93 400E
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Old 06-10-2001, 01:37 PM
Posts: n/a
Brake fluid change

I just change mine this morning,and this is what I did.
I elevated the car on all corners via jack stand.
Wheels are out for easy access to the bleeder nipples,
and will rotates tires after the procces.
Make sure you have enough fresh brk.fluid.
I ask my son to keep an eye to the reservoir,
and fill it up while its getting low.
I put 4 container big enough to catch the old fluid
out.Then I open all the bleeder w/out pumping the
brk. pedal.I just let the old fluid drip while continously
adding fresh fluid to the container.After about 45 mins.
when fresh clean fluid are coming out,I started closing all
the bleeder nipples front side first and so on.Then rotate
tires.Front to back,back to front.Took the car for a test drive and treat my son for lunch for helping.

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Old 06-10-2001, 04:13 PM
Posts: n/a

Brother of The Benz, Tobias MB
Log on at
You not only will see how to change your brake fluid but also how to make your own "EL CHEAPO" Pressure Brake Fluid Changing Unit.
This will save you $30.00 minimum.
Happy Trails Beep Beep from The Spiderman in Houston!!!
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Old 06-11-2001, 12:44 AM
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Join Date: May 1999
Location: Charlotte, NC, USA
Posts: 688
Appreiciate all the input....

But, all I've seen so far is to dilute the old fluid with new and not replace it completely. Whether it is pressured in from the master cylinder reservoir or sucked out at the caliper nipples, how would one know it has all been replaced?

Think about it...take a quart of milk and if you wanted only pure water in the container without turning it upside down, how would you go about doing this? And no, you can't siphon the milk out! Not so easy is it? The only way I see it is to remove each caliper, dump it and bleed the system with new fluid.

Any ideas techs...?

Tobias MB
4 MBs
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Old 06-11-2001, 08:00 AM
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Join Date: Aug 1999
Location: Florida / N.H.
Posts: 8,768
You can empty the calipers by opening the bleeder
and then push the pistons in using the pads
and a pair of water pump pliers.[ or clamp]
If you do this Before and After changing the
fluid, you will pretty much clean out the cal.
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Old 06-11-2001, 12:08 PM
Q Q is offline
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Join Date: Aug 2000
Posts: 839
I think the point that you are missing is that even if you can only get out 85% of the old fluid, you are still lowering the water content of the combined fluid. Being hygroscopic, the moisture content in the fluid will be dispersed throughout the entire system. Just flushing it in the above mentioned methods regularly is enough to maintain the system's components.
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Old 06-11-2001, 05:35 PM
sixto's Avatar
smoke gets in your eyes
Join Date: Jun 2000
Location: SF Bay Area
Posts: 18,745
I don't mean to sound facetious, but how much of the old remains when you change engine oil or tranny fluid? I'm sure MB doesn't intend for the brake system to be sucked completely dry before new fluid is introduced. For a reference point, ask the dealer how they replace brake fluid.

91 300SE
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Old 06-11-2001, 11:48 PM
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Join Date: Apr 2001
Location: Los Angeles CA
Posts: 154
For an ABS equipped car it is essential to use a pressure bleeder instead of any other means. For non-ABS cars it is merely preferable. One of the easiest ways to ascertain that the job has been thorough is to alternate between ATE blue and ATE gold, as has been suggested. The color change tells you when you've done the job, beyond blowing out the air bubbles and crud. It's a simple DIY and an important job to do regularly, and if you do it yourself you know it's been done right.
Richard Detoy
'84 300SD
'76 Moto Guzzi 850 Le Mans
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Old 06-14-2001, 09:34 PM
Posts: n/a
Keep It Simple

Brother of The Benz, Tobias
You have through some very pointed questions made one of the simplist maintaince jobs into a bag of worms.
First, when bleeding the brake fluid system; new fluid can not pass the old fluid when it is being expelled from the bleeders at the calipers or ABS. The new just pushes the old out of the system. NO MIXIE!
It makes no difference the position of the bleeders to the brake hoses. Put that question from your mind.
If you logged onto my "El Cheapo" look see you would have seen a DIY pressure bleeder.
Take to heart all of the help that has been passed on to you and then DO IT!
Happy Trails beep Beep from The Spiderman in Houston!!!
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Old 06-14-2001, 10:14 PM
Posts: n/a
Well said!Spiderman.

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Old 06-15-2001, 12:06 AM
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Join Date: Jan 2001
Location: oregon
Posts: 2,013
for about 4 or 5 hundred dollars and a days work you can change all four calipers loaded with new pads and a new master cylinder ,a sure way of no crud in the system! and a like new brakes system. I did this on my 81 Sd as soon as I got it as when I tried to put new pads in the front I found a frozen piston and figured that for the price of a set of tires I could replace all the importion parts and could rest easy with my brakes for some time.I pumped new fulid through the lines to clean them out before I installed the new calipers.
William Rogers.......
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