Changing brake fluid and re-doing one caliper

[The Warden]

Well, as the (hopefully) last step before re-commissioning my 300D, I'll be doing a rebuild (with the kit from Fastlane) on my right side front caliper. I'm also going to be replacing both rear brake hoses and doing a brake fluid change.

My question is this. Is there anything special that I need to know? Any tricks? On the fluid replacement, I'll be doing it the "slow" way with 3 people...one putting fluid in the resevior, one pumping the pedal, and one manning the bleed valve. As appealing as a Mityvac is, I don't have the $$ for one right now. Looking through the Haynes manual, doing the caliper rebuild doesn't look too bad, and I assume that replacing the brake hoses is just a matter of removing the old ones and installing the new ones...again, is there anything special that I don't know about? I plan to do the caliper and the rear hoses today, and the bleeding/fluid replacement tomorrow (I decided to try the Valvoline SynPower DOT-4 compatible stuff that 240 Ed was talking about earlier).

Again, any thoughts, suggestion, and comments would be greatly appreciated. This is my first time bleeding a brake system or replacing the fluid...going by what the Haynes manual says, it doesn't seem to be hard; I just want to make sure that the manual covers everything I need to know. Thanks in advance!

Haven't done job on Benz but like to use Flare wrenches on line's and box wrench on bleeder screw. These are usually brass and soft. No kinks in line if possible.Take a hose and put on bleeder nipple and into container to catch break fluid so it does make such a mess. Good Luck. Charlie

Since you have a helper, you will be better off with two person bleeding than using the mity vac. It's a great tool for troubleshooting vacuum problems, but not worth a bucket of cold spit for bleeding brakes IMHO.

Replace all the parts and rebuild your caliper. After the system is tight, empty the reservoir and pour in fresh fluid. Start at the left front and with the engine running, (so the brake booster is assisting your helper) have the assistant pump the brake pedal several times then hold the pedal. MAKE SURE THE ASSISTANT DOES NOT RELEASE THE PEDAL UNTIL YOU HAVE RECLOSED THE BLEEDER SCREW. Make sure you are communicating well with the assistant. Try to close the screw before the pedal reaches the floor. Just open it for a second to let it squirt. If it stops squirting before you reclose the screw, air will reenter. With a little practice you will open it, see the fluid shoot out and close it just as the fluid stops squirting at its maximum pressure.

After the screw is closed, have the helper pump the pedal a few more times then hold the pedal. Always confirm with the helper that they are holding the pedal down. While the pedal is held down firmly, crack open the bleeder screw again. The first time you may get bubbles and sputtering. Once you are getting a steady stream, move to the next wheel which would be the right front. Repeat. Then go to the left rear and right rear. Don't go from one wheel to the next until you are getting a solid fluid stream with no bubbles or sputtering.

After you are getting fluid from all four wheels without bubbles or sputtering, go back around from wheel to wheel for good measure. This will let you flush them further to ensure clean fluid everywhere as well as ensure that all air is gone.

After you are through with the bleeding/flushing, replace the m/c reservoir cap. Then get in and mash the pedal HARD with BOTH feet. This is to ensure that everything is strong and will not blow anything out. If something is going to blow out, you want that to happen with the car parked, not while you are on the road.

Best of luck,

[The Warden]

Larry, thanks!

How's best to get the old fluid out of the master cylinder itself? Also, I've always heard that you're supposed to start at the brake that's furthest away from the master cylinder (i.e. right rear). Not that I'm doubting you but why do you suggest to start at the left front? Also, I presume that I should leave the resevior cap off as 'm doing the bleeding?

Thanks!

[Motorhead]

First , I would never just rebuild one front caliper. They are so simple to do that when you take the first one apart to re-do, you will be ordering another kit to do the left side. Especially on front brakes, you can have brake pulling problems due to one rebuilt, free moving caliper and one,sticky,not so free moving caliper. I would also replace the front brake hoses as well...you are already taking them partially off to rebuild the front calipers and you are doing a fluid change.
To get the most old fluid out first from the master cyl, I bleed down the brakes untill the resivior is just about empty. I then refill it and go for it. My $.02 Chris

I used a 200cc syringe to suck most of the old fluid out of my master when I changed fluid. I tried to rebuild one front sticky caliper but it had some rough spots (read rust) on the piston that would not rub out so the rebuild didn't work. Ended up buying a rebuilt caliper local for very reasonable price.

[The Warden]

The reason why I was rebuilding the caliper was that, when I pulled the brakes, 3 of the 4 front pads had about half their life left while the 4th was almost completely worn away. As far as I know, the left side caliper's fine, and with how bad the car was pulling to the right before, if it pulls a little bit in either direction, I'm okay with it until the next time I do the brakes...and then I'll probably just replace both front calipers. But, we'll see how it goes; everything may be fine, eh? And I would have replaced the front hoses, but again, they appeared to be in real good condition...as compared to the rears, which were cracked in numerous places.

I got the caliper rebuilt and installed the front brakes...also got the hoses done (yet another simple task; whoever designed the 123 cars did one heckuva job!!) So, all I need to do now is re-install the air cleaner (had to remove it to do the upper control arm bushings) and bleed the system and the car should be back on the road! Bleeding will come tomorrow...

Also, rebootit, where did you get the syringe from?

Instead of a Hypo use a cheap Turkey Baster you buy at the grocery store. Also good to change power steering fluid.
Charlie

Syringe came from a local vets office. I do web services for several of them so just went in and asked for one. Turkey baster would work just as well.

[Antony]

I know you've heard alot already, and I'm not trying to overwhelm you but.... When your assistant pushes down on the brake pedel, make sure that they do not push the pedel too far past it's normal travel distance. The master cylinder can, over time, develop rust spots around the area that is not normally used. If you move the piston into these areas, you may score the piston / seals and this will give you porblems (think leak-down) later on. It may not help but I just thought you may want to keep this in mind. Best of luck.

[jcd]

Use Jim Smith's approach in the attached thread for bleeding the brakes.

Brake Pads

It is the hot set up and better than the method described in the Haynes manual.

JCD

I've seen posted here a few times the recommendation to start bleeding at the rear. This makes no sense to me for bleeding, for flushing, it doesn't matter, but with a system that has been almost completely opened as will be done by the original poster of this thread starting with the caliper closest to the m/c makes sense.

You get the air out of the near one, then go the one next farthest away and so forth. If you start with the far one, you then have air left in the system at the near one that will get pushed further down the long line leading to the rear.

It has worked for me. The main thing is that you do what works well for you and that you flush thoroughly so that fresh fluid is present everywhere.

Good luck,

[leathermang]

I have always been told that one starts at the farthest away bleeder and then to the next longest...(30 years)
Perhaps, since there is some pushback ( more in standard brakes) it provides a clean supply for the other three with no chance of old fluid backing up to a junction and being left in the system ....if one uses enough fluid and makes sure it is clean.. and checks it twice I doubt it makes any difference...
Well, maybe it makes a difference on air bubbles... ?
I agree with Motorhead... the rule is that you always do stuff to brakes to one axle at a time.. both front or both rear or all of them... but never to one brake...