Ooops! Soft Pedal after bleeding, Does cracking the MC lines work? - PeachParts Mercedes-Benz Forum

warmblood58 · #1 04-25-2010, 01:01 PM

Just finished up R&R the front calipers, rotors and lines on my 123 wagon and now have a soft pedal after thoroughly power bleeding. I did remove the MC to clean reservoir and check vac booster and I now believe that I need to bleed the MC. If I have an assistant slowly pushing in the pedal and I crack each of the three lines will this work well to eliminate any remaining air bubbles in MC? Should I also elevate the rear of the car to level MC? Thanks!

vstech · #2 04-25-2010, 01:09 PM

if you have air in the MC, you need to bench bleed it.
it's best to remove it, and attach bench bleeder hoses into the reservoir and pump until all the air is gone, then reconnect to the car and re-bleed the lines/calipers.
unless you have a reverse bleeder. it will bleed the MC too.

warmblood58 · #3 04-25-2010, 01:16 PM

Quote:

Originally Posted by vstech

if you have air in the MC, you need to bench bleed it.
it's best to remove it, and attach bench bleeder hoses into the reservoir and pump until all the air is gone, then reconnect to the car and re-bleed the lines/calipers.
unless you have a reverse bleeder. it will bleed the MC too.

Damn, I will have to make a kit as this is not a new MC. Cracking the lines will not work?

vstech · #4 04-25-2010, 01:26 PM

nope. not well anyway. you have to push and pull to get the air out. and it's just SOOOOO slow without bleeders.

kmaysob · #5 04-25-2010, 01:49 PM

cracking the lines WILL work. ive done it many times.

warmblood58 · #6 04-25-2010, 01:51 PM

Quote:

Originally Posted by kmaysob

cracking the lines WILL work. ive done it many times.

I would think so upon reflection - I will try this first, then rebleed and see what kind of results I get and then report back -thanks!

Brian Carlton · #7 04-25-2010, 05:40 PM

Quote:

Originally Posted by kmaysob

cracking the lines WILL work. ive done it many times.

I've done it as well........but, it's a PITA and brake fluid goes everywhere........where you don't want it.

Far better to get the metric kit from NAPA and simply run the hose back into the reservoir. For $12. it's well worth it.

leathermang · #8 04-25-2010, 06:20 PM

Quote:

Originally Posted by Brian Carlton

Far better to get the metric kit from NAPA and simply run the hose back into the reservoir. For $12. it's well worth it.

X10

69shovlhed · #9 04-25-2010, 10:55 PM

or just crack the lines and stuff some old rags underneath so the fluid don't get all over your car. have the pumper push slowly but firmly, and don't open the fittings so far that fluid blows everywhere. then re-bleed at the wheels rr, lr, rf, lf.

Diesel911 · #10 04-25-2010, 11:36 PM

Quote:

Originally Posted by kmaysob

cracking the lines WILL work. ive done it many times.

I agree.
Just make sure you tighten the line Fittings when your assistant is holding the pedal all the way down and only loosen the Line Fittings when the Brake Pedal is all the way up.

Put some raggs or Paper Towels under the Master Cylinder to control the Mess. It should take at the most 4 pumps to Bleed a MC.

warmblood58 · #11 04-26-2010, 01:26 AM

Quote:

Originally Posted by Diesel911

I agree.
Just make sure you tighten the line Fittings when your assistant is holding the pedal all the way down and only loosen the Line Fittings when the Brake Pedal is all the way up.

Put some raggs or Paper Towels under the Master Cylinder to control the Mess. It should take at the most 4 pumps to Bleed a MC.

actually it is the other way around, assistant pushes pedal down, open fitting, then close and and then then let assistant allow pedal to return up -

warmblood58 · #12 04-26-2010, 01:28 AM

Quote:

Originally Posted by 69shovlhed

or just crack the lines and stuff some old rags underneath so the fluid don't get all over your car. have the pumper push slowly but firmly, and don't open the fittings so far that fluid blows everywhere. then re-bleed at the wheels rr, lr, rf, lf.

I agree! Worked great! I pushed a towel underneath MC, and held a paper towel at each fitting as we did the work. Huge difference and sponginess went away. Oh, I did raise rear end to level out MC and did rebleed each caliper in the proper sequence. THERE IS NO NEED TO REMOVE MC AND BENCH BLEED -WASTE OF TIME

Diesel911 · #13 04-26-2010, 11:01 PM

Quote:

Originally Posted by warmblood58

actually it is the other way around, assistant pushes pedal down, open fitting, then close and and then then let assistant allow pedal to return up -

Loosen the fittings with the Pedal all the way up and then the assistant pushes down on the Pedal sqirting out the Fluid and Air.
The assistant holds the Pedal all the way down while you tighten the Fittings so on Air gets in during the next step.
Assistant releases the Brake Pedal sucking Fluid into the Master Cylinder.
Repeat the above until the Air is bleed out.

I added this later: The above represents the way I do it and the reasons and it may differ from how others do it.

69shovlhed · #14 04-26-2010, 11:24 PM

bench bleeding is for a new or rebuilt unit that is empty when you start the job. once your done bench bleeding you still want to bleed at the master until its flowing a constant stream of fluid, then bleed the wheels. if you are only replacing a bad master and not doing any other work on the hydraulic system, you can sometimes if your careful only bleed the master and not need to bleed the wheels at all.