Bench bleeding won't do anything to fix worn seals. To my knowledge it's usually performed on new master cylinders before installing but it could be done mounted I suppose. I'm not familiar with your auto but in general you would have to remove the out going lines and install different ones which bend up to the reservoir(s) with the cap off. New MC's sometimes come with plastic ones for this purpose. Then someone would have to pump the pedal while someone watches the fluid being cycled until there are no air bubbles present. It's just ensuring all the air is removed from the MC before installing and performing the rest of the brake bleed procedure. In my experience, a bad master cylinder is usually evidenced by the brakes working fine at first but then the pedal going to the floor (usually slowly unless the seals are really gone). BTW, apparently cars with anti-locks will do this too if you press really hard, it prevents too much pressure being applied the the system. If it's bad seals however, the car may move forward while if it's the anti-locks it shouldn't. Try checking your flexible rubber hoses while someone presses the pedal. I've seen these swell up (balloon) and cause soft brakes long before they fail.

 

...you would have to remove the out going lines and install different ones which bend up to the reservoir(s) with the cap off. New MC's sometimes come with plastic ones for this purpose. Then someone would have to pump the pedal while someone watches the fluid being cycled until there are no air bubbles present.

I did get a couple of green plastic plugs that look like they attach to the clear plastic/rubber hoses that also came with my master cylinder.

What exactly do these attach to? The outgoing lines that I disconnected with a line wrench? or the incoming two holes from the reservoir? If I use the clear plastic hoses to attach to the reservoir, what do I do about the two holes where the actual brake lines attach? leave them empty?

Sorry for so many questions. Like I said, by searching google, you'd think NO ONE has ever done this procedure before.... or no one thought it was different enough to consider it worth documenting.

Thanks,
-Jim

 

Oh no, I'm sorry for the poor communication. I am doing a complete remove and replace. I'm not trying to salvage the old one (well, I am returning the core to the manufacturer)

I have never done a bench bleed on an MC that didn't have the reservoir attached... but you are correct, this one came with little plugs and hoses so doing it on the vehicle shouldn't be too much of a problem. I will give it a shot this evening.

Thanks,
-Jim

 

The plastic pieces attach to where the out going lines would be. The plastic hoses press onto those and run up to the reservoir. The top of the reservoir should be open and filled with new fluid. Then you work the brake rod to pump the fluid cycling it thru the hoses until there are no air bubbles. Are you saying the reservoir is separate from the master cylinder? Does the master cylinder attach to the reservoir thru lines? Or directly? Sorry, I'm not familiar with your vehicle, just years of shade tree mechanics. Have you tried Youtube? Amazing what you can find. Maybe just watching a regular MC bench bleed will help you figure out what you're trying to accomplish. Which is, get the air out of the new MC before installing it.

 

Nope, the reservoir is mounted up on the firewall right near the hinge to the hood. It has hoses that run down to the master cylinder. I've done clutch master/slave cylinders before and did a brake master cylinder before on a GM. It was far easier as the reservoir was attached.

The green "plugs" that came with my master cylinder do not fit. I may have to go pick up a couple of kits at the parts store.

I've never seen one like this but I rarely work on cars these days. I'm not going to go spend $600 to $1500 for a mechanic to do it though...

 

So if the reservoir is completely separate from the MC can you run the hoses to the opening(s) where the reservoir or lines from it connect? Cycle fluid thru it that way? Otherwise I think you'll need to install the MC, don't connect the outgoing lines however. Put in the plastic connectors and run the hoses into the top of the reservoir. If you need longer hoses, get them. Fill the reservoir and have someone else pump the brake pedal until you have the air out. Then connect the outgoing lines and bleed the rest of the brake system as normal. Hope this helps. Good luck.

 

Thanks for clearing that up. I was afraid to mount the master cylinder and use the brake pedal to do the bleeding.

Thanks again,
-Jim