renewing brake fluid

[rallen]

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.

[t walgamuth]

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

[rallen]

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?

[t walgamuth]

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

[blueranger]

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.

[t walgamuth]

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

tom w

[rallen]

Originally Posted by blueranger

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.

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

[Arthur Dalton]

Originally Posted by blueranger

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.

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 !!!

[Gerard]

Well I have followed this thread with amazement at the level of knowledge known about brake fluid. Some guys have a good engineering knowledge and can put across a point convincingly and with a scientific and reasoned proof. Some others would be better preparing a large bird for thanksgiving!!

I decided to have a look on the internet and found this page which refers to a NHTSA study on the subject.

http://www.findarticles.com/p/articles/mi_m3102/is_9_123/ai_n6221217

Hope this helps,.......
Gerard

[Mad Mick]

Everything on Earth has movement.... Everything.....
the brake piston is in the master cylinder located on the firewall.... the caliper is at the wheel. without compression with just heating and cooling the fluid would be circulating on its on slightly. Its circulating as your car is sitting in the driveway right now... (however slight)

I'm looking out at the Atlantic ocean circulating; Now I know the moon has a big pull on an awful lot of water, could this help circulate brake fluid in the car in my driveway?

This is a brilliant, if not somewhat scarey thread.

Long may it continue.

Vincent.

[rallen]

That article is good. I am not sure about the bit where it says when the ABS activates there is circulation in the circuit. That cannot possibly be correct for the fluid in the hoses and the calipers - it just does not make sense. There is no device I can think of that will circulate fluid when one end of the system is completely closed. You can not push the fluid further and you cannot draw it up.

Unless, unless, unless: on systems with ABS there are return hoses from the calipers. I have not observed any such return hoses on any cars I have serviced. Has anyone else?

Also, as the article says the ABS has valves etc that need to be activated in order to facilitate the fluid change. We at home, how are we going to do this? I plan to change fluids tomorrow, any help appreciated

Originally Posted by rallen

Unless, unless, unless: on systems with ABS there are return hoses from the calipers. I have not observed any such return hoses on any cars I have serviced. Has anyone else?

Also, as the article says the ABS has valves etc that need to be activated in order to facilitate the fluid change. We at home, how are we going to do this? I plan to change fluids tomorrow, any help appreciated

I know nothing about ABS system design. My personal solution is to keep driving 20 year old cars so I don't have to deal with it. I hate the feeling of ABS anyway. Unfortunately, this may become one more thing that can't be done without specialized equipment.

[mctwin2kman]

Bleeding ABS is the same as standard. Never seen anyone do it any diferent!