Bench Bleeding a Master Cylinder

by Mcarlo77 Wed Jul 24, 2013 9:49 pm

Need some reassurance from someone who's done this with the plugs (not the tubes that loop back into the reservoir). Okay...so, I buy a NEW M/C from RockAuto. I guess the new method of bench bleeding these days is to use the threaded plugs they include to block off the outlet ports and then push in on the plunger on the end. I'm reading the instructions and first they say to pour brake fluid into the reservoir and watch as it starts to drip from the two open outlet ports (plugs not to be installed, yet). Well, the rear port did just that...but, the front port didn't drip anything. Thought...okay, on to next step anyway. Put the plugs in and put the M/C on my bench and start to push in on the end plunger to bleed. Instructions say I should push it in no more than 3/4"-1" and slowly let it back out. I couldn't push it in more than 1/4"...no matter how I tried. Is this normal with this method of bleeding? Even tried a c-clamp to gently push it in...but, it started forcing fluid out around the front plug, so I backed off. I'd get a single bubble with each pump (thought I'd get a series of bubbles with each pump). I continued bleeding it by hand and finally, after maybe 15-20 mins the bubbles disappeared while fluid started circulating within each bowl with each pump. I'm assuming it's bled? I'm just questioning the method and hoping I don't have a bad M/C since the front port didn't drip initially and I couldn't pump the plunger more than a 1/4". Any thoughts?

by ant7377 Wed Jul 24, 2013 10:33 pm

I had trouble withthe damn thing too. Those instructions suck,I still have the tubes with the little clips that pumps the fluid back in, I like that way better,to tell you the truth I think this is why I never have a really hard pedal I can never seem to bleed the master properly even with the tubes I always seem to have a bubble.

by ant7377 Wed Jul 24, 2013 10:40 pm

https://www.youtube.com/watch?v=9bEPrO99B5A

by Mcarlo77 Wed Jul 24, 2013 11:27 pm

Yeah...the guy in the video just casually pushes in and out on the end plunger. Hell, I've got a blister on the palm of my hand from having to push so hard against that plunger with my screwdriver. Guess I'll work it a few more minutes before I install it tomorrow and see what happens. Next, I'm going to try the gravity method of bleeding my brakes. Never done that before, either. Usually have someone to pump the pedal for me. I have one of those cheap hand operated vacuum pumps, but tried that once on my Monte and wasn't impressed.

by 77mali Thu Jul 25, 2013 6:54 am

I bought a new one a while back and did the method you mentioned with the threaded nipples & lines going back into the chambers. You have to have it dead-a$$ level in a vise for this to work 100%.

by Wallyuph Thu Jul 25, 2013 9:20 am

You can buy the tubes at any parts store pretty cheap. Those plug ideas did not work for me. I got my tubes out and sure enough still had air in it. The gravity bleed works well but does take some time open all four bleeders and keep checking master every so often. We still have a helper pump and hold after gravity bleeding here. Start with the farthest away wheel in the rear (pass side) when pump and hold method.

by thatfnthing Thu Jul 25, 2013 9:54 am

Mcarlo77 wrote:Next, I'm going to try the gravity method of bleeding my brakes. Never done that before, either. Usually have someone to pump the pedal for me. I have one of those cheap hand operated vacuum pumps, but tried that once on my Monte and wasn't impressed.

I've tried the vacuum one, and I've tried the pressure one. They all suck horribly, and the pressure one makes a hideous mess. There is no substitute for pumping the pedal, because only that method will generate enough pressure to force the air through the lines. This became especially true when I upgraded to ABS. The only thing I would do differently is get some speed bleeders for the calipers and wheel cylinders so I don't have to have an assistant.

by Joe73 Thu Jul 25, 2013 9:55 am

I've had great luck bleeding brakes with the vacuum pump. I do all my vehicles every 3 years to get the dark colored (moisture laiden) fluid out. Real simple and a one man job.

Havent done a m/c in a long time but I've always clamped it in a vice, put the tubes on and pump it up.

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