brake bleed - PeachParts Mercedes-Benz Forum

adiaw83 · #1 05-02-2003, 09:59 PM

I have a 300sd and I plan on bleeding the brakes this tuesday. I have a liter of brake fluid but I do not have any suction tools like the eezibleed. I planned on doing it traditionally by connecting the valve to a hose and just opneing it up. Can someone tell me the proper procedure or any suggestions. Thanks

dmorrison · #2 05-02-2003, 10:18 PM

To do it the old fashion way you need a helper.

You attach a drain tube to the caliber bleed screw fitting. A clear tube is best.
The other end of the tube is into some kind of container to catch the old brake fluid. I usually have the tube leave the bleed screw and move up vertically 1-2 inches. this way I can see the fluid bubbles and dirt as it comes out of the bleed screw. If the tube goes straight down you won't see the bubbles as well.

Have the helper press and hold pressure on the brake pedal. When the brake is held you open the bleed valve ( 10mm wrench I think) and allow a small amount of fluid to bleed out. Before your pressure reduces to zero you close the bleed screw.
Then have helper release the brake pedal and press and hold it again. You do this "cycle" until you get clear fluid coming out of the caliper with NO bubbles. Do this to eliminate any air bubbles and to flush the brake lines and calipers of old fluid. If you are doing the entire system start at the farthest caliper. the right rear. then go to the left rear, then the front right then the front left. Longest distance from the master cylinder to the shortest. Consider removing as much of the old fluid from the master cylinder reservoir as you can, refill with clean NEW fluid. Your now starting with clean fluid and a full reservior.

My daughter and son use to help be with this. It would go something like this.

Me: " press"

S/D: would press and hold the brake pedal.

Me: I would open the bleed screw for a couple of seconds watching the fluid for dirt and air.

S/D: Would hold the brake pedal

Me: After I close the bleed screw I would say "cycle"

S/D: They would then let their foot off the pedal and reapply the pressure to the pedal and hold it.

Me: I would open and close the bleed screw as above

Repeat untill the fluid is clean and free of bubbles.

Watch out for spilling brake fluid on the paint. It's the best known paint remover.
Make sure you refill the brake reservoir after a couple of "cycles".

This system will work for both antilock and non-antilock brakes.

I recently bought the pressure bleed sytem. It is well worth it.

Dave

adiaw83 · #3 05-03-2003, 09:22 PM

thanks a lot thats all i needed. I have a liter of fresh brake fluid. Do you think thats enough? What do you mean by this in relation to the line position though

Quote:

I usually have the tube leave the bleed screw and move up vertically 1-2 inches.

dmorrison · #4 05-03-2003, 09:45 PM

1 liter should be enough

The clear plastic tube that the old fluid drains through.
Attach it to the bleed screw on the caliper.
As the tube goes from the bleed screw it follows a path that initially moves upward for 1 or 2 inches then I usually loop it over the sway bar or through the steel brake line that is on the wheel well wall. Place the other end of the tube into a container to collect the old fluid. When the fluid goes into the tube it initially goes upward before it flows over the u turn in the tube and drops into the container. An amount of the brake fluid will stay in the section of tube from the bleed screw to the U turn. You will see the dirt and bubbles much better in the fluid that does not get over the turn in the tube. If the tube is clear. If the tube is black rubber your not going to see much *G*.
Its only a technique, not required.

Dave

#5 05-03-2003, 09:54 PM

Just one other thought--

If the fluid hasn't been changed for a long time, it might be a good idea to place a small wooden block under the brake pedal to keep it from going all the way to the floor. If the fluid is really old and there's gunk and/or rust in the master cylinder, you can damage the seals (scrape the edges) by pushing the pedal all the way to the floor. The wooden block will put a limit on how far you can push the pedal down.

If the fluid has been changed regularly and the system is well maintained, this won't be a problem.

I just got a speedi-bleeder last fall--much better system that pumping the pedal!!

adiaw83 · #6 05-04-2003, 02:12 PM

ok thanks I think im going to try this out on tuesday.

jcd · #7 05-04-2003, 05:24 PM

Read Jim Smith's advice.......he's the best.

Brake Pads[/url]

Also, hit the bleeder valves with some penetrating oil a day or so before you start so they are easy to loosen.

Good luck,

JCD