85 W123 Brake Bleed Coming Up
 

I need to bleed my brakes and want to follow Army's recommendation about bleeding with the engine running. Do I have the second person pump on the brake pedal, hold hard, then I open the bleeder and watch for all bubbles to stop? Do this on all 4, watching closely the fluid level in the reservoir. I plan to put a block of wood under the brake pedal and bleed in the proper sequence. Rear brakes were recently completed, new calipers and rotors. Fronts are OK and bleeders are not seized. My problem is a low pedal and excessive effort to stop the car compared to how it was before.
I used a Motive Bleeder before and bled the brakes by myself and am thinking the pump-the-pedal method may be required for this car.
Last warm day in the US NE is Sunday :-(

I use this on my W124:
http://img607.imageshack.us/img607/2543/p4257566.jpg

It's a brake reservoir lid like it's usually used on these older benzes, with a hole in the middle, and a tire valve from a bike stuck trough there. Then the rubber seal that is normally in the lid is put ontop of the tire tube thats now in the seals place, and the whole assembly is screwed onto the reservoir.

Works like a charm, just don't go above 1 bar (especially if you use a compressor, the lid might blow off*) and assure that the reservoir doesn't run dry, but you probably know that :P


*Don't ask how I know :o

The Motive bleeder works like this. The screw on cap provided with the thing fits right on the reservoir and one pumps up the motive thing to about 15 lbs. It really seemed to work OK but the brake is still too low and mushy and pumps up some with repeated pumping of the pedal, classic air in the lines action. I think my MC is OK but at 193000 maybe it's sort of beat too.

I have a Motive Brake Bleeder, and have used it on several 123`s, as well as my own 85 300D. works very well.

What do you believe is different with the 85 model year?

Charlie

The Motive bleeder rocks.

Hook it up, fill it up, pump it up, and go to each wheel and crack the bleeder until you see new fluid.

No need for a helper pumping the brakes, no worrying about the reservoir going dry, total piece of cake.

I will never bleed the old school way again.

I bet when I replaced the back brakes and used the Motive bleeder I got air in the lines from not being careful about the fluid. I didn't put fluid in the Motive canister, just used it to build up pressure for the bleed. Going to buy 2 qts of fluid and fill the Motive thng and try again, all 4 brakes. I know the thing works, I just must have screwed up.

Be sure to release the pressure in the motive, before you unscrew the master cylinder cap when you get through.

when the pressure us released, it will suck back the fluid in the line back to the container. and your MC will be at the correct level.

NOTE: make sure that the tubing on the motive is good. I was under the R/R bleeding the caliper, and suddenly heard water dripping, instead it was brake fluid dripping down under the engine.

rushed up to the engine and there was brake fluid spraying all over the fenders, hood eng etc...:mad: the vinal tube cracked at a fitting, I have had this for quite a while. replaced all the tubing and back up and running.

I sure was running to get the mess cleaned up before it did any damage to the paint. Just another day in "DIY". :)

Charlie

And done! Pedal is a bit higher and more firm. I'm thinking to replace/rebuild the MC on the next go-round as the car's nearing 200K. Front brakes look pretty good as far as pad wear but the wires leading into the chassis for the pad wear indicators are very much shot. Maybe in the spring. Anyway, the Motive Bleeder when used as intended works pretty much perfectly. I plan to fiddle with it to build adaptors for my other cars using JY reservoir caps and tirevalve parts.

remember when using automotive caps, to seal the vents and vent paths in the caps! very messy if not sealed up!

Speaking of spraying down the engine compartment:eek: with brake fluid. You better be sure those two little black caps on top of the reservoir are not cracked before pressurizing the system , most I have seen are.

X2, yeah mine are good.

I think those are a replaceable item, the bird might have them. I think Fastlane (Phill) had them when it was up and running.


I just don`t need another one of those surprises. :D
It`s funny now, but sure not when it was happening.

Charlie

Black-capped Reservoir
 

The "Black-capped Reservoir" is a common bird in DIY-land. I saw one when I bled the brakes in my wife's car for the first time. Not a happy sight. Here's the one I removed -- it had a patch sawed off, I don't know how, before I got the car. Aside from fluid leaking all over your nice clean car, you can't pressurize the system if the cap leaks. New caps should be available from Pelican or your dealer.

http://i323.photobucket.com/albums/n...Cover_4130.jpg

Pressure bleeding is certainly the way to go. A pressure of 10 psi works well for me although FSM says higher for ABS-equipped cars. My bleeder was home-made from an inexpensive small garden sprayer. I wash it out with hot soapy water after using it and make sure it's dry before putting it away for "next time."

http://i323.photobucket.com/albums/n.../Pump_4133.jpg

I surround the reservoir with towels just in case there's a leak.

http://i323.photobucket.com/albums/n...Flush_4131.jpg

Another possible problem I've heard about the "pump and hold" method is that the assistant pushes the pedal all the way to the floor; this pushes the piston into the unused and rough part of the master cylinder, possibly damaging the seal and causing future (internal) leaks.

Jeremy

Yah, the pressure bleeder is the way to go. Mine is a "Speedie Bleeder", gets air pressure from the R/F tire. I 'll be looking for a new one, the gauge is acting up.