renewing brake fluid
 

Is there a correct procedure for doing this? I was thinking of undoing the bleed valves of the rear calipers and having someone depressing the brake pedal while I am topping up the master cylinder: eventually the old fluid will be completely out of the system. Then do the same for the front calipers.

the correct way
 

is to start with the caliper furthest from the mc and work you r way back to the front. you need to pump it up and bleed off the pressure. close the petcock and pump up.... etc over and over. if you leave it open and just pump the pedal you will fill the line with air bubbles.

ask how i know...no dont.

tom w

I just read another 2 threads discussing this. The question is since you are constantly topping up the master cylinder's reservoir, when do you know the old fluid is completely out?

Another question is about the calipers: there is always a lot of fluid in the calipers' pistons, the more worn the pads the more fluid. How do you remove that fluid completely? Just because there is fluid coming out of the bleed valve does not mean it is (only) the old fluid... I do not think it is worth dismantling the caliper so as to push the pistons all the way back for this operation (too long winded).

And another question about the brake pump: if there is such a pump in the system, might it not have its own reservoir - how do you drain that?

sorry
 

i forgot to tell how to know when the fluid is purged. put a small clear hose on the nipple of the bleed valve. run it down into a clear jar. watch the fluid coming in until it is clean. the old fluid will be darker. there is no brake pump, just the master cyl. and the calipers.

well you dont say what year car. is there a anti lock system? if so i am not sure how this affects but i believe it will be the same. pump til you get clear out the other end then move to the next caliper.

tom w

correct diy method
 

the correct method for a diy'er is to go to the dollar
store and buy a turkey baster.... suck out the resevor
and add the new fluid... do this once a week for 4 weeks
and your completely changed. :D

i hope
 

you are kidding. this will only waste your fluid and never get it completely clean. it is better than nothing ... just.

tom w

How is that going to change the fluid in the hoses leading to the calipers and the calipers themselves?

I do the turkey baster method once a year. I do it over a period of 3 or four days. I do the same with power steering fluid.

I don't understand how this is accomplishing anything for the brakes. The old fluid in the rest of the system is not being replaced. This is like flushing your cooling system by just emptying and refilling the reservoir. It may make sense for the PS, because the fluid circulates through the system.

it reminds
 

me of people who never change their oil ...just add. it is a little better than not doing anything but not much.

tom w

I don't know...my brake fluid is always clear... when I change out the pads..I will typically do a quick bleeding...but I don't drain the system down.

cars with ABS require pressure bleeding per the MB shop manual.

Problem with the old pumping the pedal method is you are pushing the [iston cups beyond their normal travel point. That area is where the crude will lie and this ussually shortens the M/C life. Much better to either pressure bleed or on older cars you can use something like a vacuula.

Michael

That is the Correct method for "Used Car Lots".

How long have you been defying the Laws of Basic Physics ????

What Magical Route does the fluid in the calipers take to get back into the res . ???

Are we to believe that it is the Invisible line we can't see ????

So many questions , so many wrong answers ,, and with Conviction !!!

Usually, you are safe if you only pump the pedal 1/4 - 1/2 of the way down. Also, you can still bleed them manually regardless of ABS. It's the traction control systems that you have to worry about.

OK so my E320 year 2001 has ABS and traction something. I am sure that if I draw a lot of fluid from the calipers and renew some in the master cylinder by means of draining first what's in it and then refilling it with new, I will have achieved a lot - there cannot be many places left where fluid may be stored?