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Need help bench bleeding MC


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Okay, so I have not done it myself before, but I think I have the general procedure down. I still have some questions however.


This is the set I received from RockAuto. A remanufatured Nabco MC. The kit came with two bleeder lines and two green plugs (adapters?). I have the reservoirs and fittings that I will be bolting on soon.

Now I believe this is how I do it but I am not 100% sure. Please correct me if I am wrong at any point in this procedure.

1. I screw these small green adapters into the bottom two openings of the MC.


2. Once the reservoirs are on the MC, I place the MC onto a vice.

3. This next step confuses me a bit. I know I am suppose feed the lines from one of the pairs of openings back into the reservoirs. I am not sure if I feed them from the two bleeders on the side of the MC or the two green plugs (adapters) from the bottom? I believe I do it like this:


This correct? :stupid:

4. Once all the air is gone, how exactly do I bolt it onto the car without losing a crap ton of brake fluid? Once I remove the lines I am assuming brake fluid will start crapping out of the MC non-stop all over my paint :finger:

Also is a philips screw drive okay in place of a pushrod?

Any assistance would be greatly appreciated!! :rolleyes:

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In that case would I bolt the MC up to the booster and the bottom two brake lines, then put the lines on the side bleeders feeding them back into the reservoirs? Or

bolt up to the booster, keep the side bleeders shut, and bleed from

the bottom two feeding them back into reservoirs?

I'd imagine it's the first procedure by keeping the bottom two bolted to the brake lines and bleeding from the bleeders. But if there's no fluid in the system, wouldn't

that just suck air in?

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So you did it how I did it, then when you did the final bolting to the bottom two lines, you pulled the plugs out and rescrewed? Did you lose some brake fluid in the process? I'd imagine if you took the plugs out to bolt onto the lines, fluid would just drop out....

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I bled mine on the car and even with all the hydraulic lines connected. Get everything connected normally, fill both reservoirs with fluid and bleed each reservoir one at a time with the tube feeding from the main cylinder bleed nipple (on the side of the cylinder) back into its reservoir like your picture shows.

I did it with the car door open, I worked the pedal with my foot and was leaned out over the fender/cowl holding the tube over the reservoir. A bit cumbersome, but it worked just fine. Took many pedal pumps, slow and complete, before I stopped seeing bubbles in the tube. Once you get one done, make sure to tighten the bleed screw and put the cap on the reservoir before beginning the next one.

May not be the best way to do it, but my brakes feel confident and predictable so I guess everything is free of air.

p.s. - make absolutely sure you add the step of packing towels or blankets under and around the master cylinder so drips of brake fluid don't end up on painted surfaces.

Edited by BTF/PTM
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The directions that came with my MC reads as follows: 1) Clamp MC securely by mounting flange to bench vise. 2) Remove and discard factory installed protective plugs from the outlet ports and place a catch container under the MC. 3) Fill the reservoirs with new brake fluid. When the fluid begins to drip from the outlet ports, securely install threaded plugs. This provides lubrication to the piston seals before bleeding. 4) Using a bleeding tool or other suitable bleeding tool, begin slowly depressing the MC piston using 3/4 to 1" strokes. Wait 15 seconds between strokes to avoid aeration of fluid. Continue this procedure until the piston can't be depressed more than 1/8" and no air bubbles are visible in the fluid reservoir. 5) Remove the MC from the vise and install in vehicle, leaving the plugs installed. 6) Remove one plug at a time and connect the steel brake lines from the vehicle to the MC. 7) The wheel cylinders and calipers must now be bled to remove any remaining air in the system. I would think layers of towels are always a prudent idea. Good Luck!

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