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Mike S.
Mike S., ASE Certified Technician
Category: Ford
Satisfied Customers: 7011
Experience:  ASE Certified Master Technician
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How exactly do you bleed a master cylinder when its still

Customer Question

How exactly do you bleed a master cylinder when its still hooked up to your vehicle and you lost all fluid through your rear driver side cylinder while your driving down the road?
Submitted: 7 months ago.
Category: Ford
Expert:  Mike S. replied 7 months ago.

To bleed the master cylinder while on the vehicle use the lines like a bleeder screw. In other words, pump the brake pedal up slowly as to not cause bubbles, then hold it down and crank 1 brake line loose at the master cylinder, then tighten the brake line back up before lifting up on the brake pedal. It don't usually matter which one is done first, then do it a few times and then switch to the other brake line at the master cylinder.

Customer: replied 7 months ago.
Break fluid is filled up to the full mark in the master cylinder and isn't moving when pumping the pedal.
Expert:  Mike S. replied 7 months ago.

Perhaps the master cylinder is bad. Is this a new master cylinder? Did you fix that leak at the rear driver side cylinder?

Customer: replied 7 months ago.
we fixed the leakk by installing new caliber, new rotors and new brake pads in the bank. The master cylinder ran completely dry and the pump comes on when you push the pedal down.
Expert:  Mike S. replied 7 months ago.

Do you get any fluid out of the brake lines at the master cylinder when trying to bleed it?

Customer: replied 7 months ago.
Are you there?
Expert:  Mike S. replied 7 months ago.

yes

Expert:  Mike S. replied 7 months ago.

did you not see my reply, "Do you get any fluid out of the brake lines at the master cylinder when trying to bleed it?"

Customer: replied 7 months ago.
No we don't but the pump turns on
Expert:  Mike S. replied 7 months ago.

Replace the master cylinder.

Customer: replied 7 months ago.
We just need to bleed or prime it while its in place. How do you do that?
Expert:  Mike S. replied 7 months ago.

That was the very first thing I told you.

To bleed the master cylinder while on the vehicle use the lines like a bleeder screw. In other words, pump the brake pedal up slowly as to not cause bubbles, then hold it down and crank 1 brake line loose at the master cylinder, then tighten the brake line back up before lifting up on the brake pedal. It don't usually matter which one is done first, then do it a few times and then switch to the other brake line at the master cylinder.

Customer: replied 7 months ago.
Can we mess the electric pump up if we have a air lock in the master cylinder
Expert:  Mike S. replied 7 months ago.

No, but you will most likely have to bleed that abs pump as well. when done.

Customer: replied 7 months ago.
How do u bleed the abs pump
Expert:  Mike S. replied 7 months ago.

here are the instructions,

Expert:  Mike S. replied 7 months ago.

Did that answer your question? If so, kindly leave me a positive rating, so I get credit. If you have any more questions, go ahead and ask.

Customer: replied 7 months ago.
We read the instructions however we did not see anything that mentioned the abs pump or any pump so we would like to know if we continue bleeding the rear brake cylinders per your instructions and the pump continues to come on as we press the pump can this cause any other damage to any other system. Please advise approximately how many times we should follow this procedure before seeing results.
Expert:  Mike S. replied 7 months ago.

Then you missed it, "

HINT:

a. Air is bled as the pump motor operates while the brake pedal is being

depressed.

c. As brake fluid is continuously drained while the pump operates, it is not

necessary to repeatedly depress the brake pedal.

g. With the brake pedal depressed, loosen the bleeder plug of the rear disc brake

cylinder RH, continue to hold the brake pedal and allow brake fluid to be

drained from the bleeder plug while the pump motor operates

Customer: replied 7 months ago.
OK thank you I will tell my husband. I appreciate your time
Expert:  Mike S. replied 7 months ago.

Did you happen to catch the bleeding sequence that starts at the rf, then lf, rr then lr.

Customer: replied 7 months ago.
No what is rf if RR and ir?
Expert:  Mike S. replied 7 months ago.

Right front, left front, right rear and left rear, that appears to be the order that they are bled. The exact opposite as normal.

Customer: replied 7 months ago.
OK thank you so much we will try it now and get back with you tomorrow if we need help...lol
Expert:  Mike S. replied 7 months ago.

ok, tomorrow is fine but I have to warn you, I haven't been getting to sleep until into the wee hours of the morning, last nite 5am, so I don't get up till way past noon until I see my doctor and get back on track.

Expert:  Mike S. replied 7 months ago.

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