Bench Bleeding Master Cylinder Question
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Staging Lane
Joined: Jan 2004
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Bench Bleeding Master Cylinder Question I just finished plumbing the brakes on my 69 Camaro. All late model LS1 calipers, new master cylinder and booster, Stainless brakes hoses, Adjustable Proportioning value, etc. A question concerning bench bleeding the new Master Cylinder:
1) I can't remember the details beyond placing the MC in a vise with brass plugs and adding fluid and pushing the piston a few times to remove the air. But once I remove the brass plugs to install the regular lines doesn't air re-enter the master cylinder off -setting the prior bleeding? Or does the fluid running out while connecting the regular brake line stop the air from re-entering so it's not a problem. Please advise and thanks in advance for your response!
1) I can't remember the details beyond placing the MC in a vise with brass plugs and adding fluid and pushing the piston a few times to remove the air. But once I remove the brass plugs to install the regular lines doesn't air re-enter the master cylinder off -setting the prior bleeding? Or does the fluid running out while connecting the regular brake line stop the air from re-entering so it's not a problem. Please advise and thanks in advance for your response!
Place MC in a vice, install temp brake lines that go into a container of some sort and submerge those lines. Fill the reservoir.
Pump the MC piston and watch for the air leaving the temp lines in the container.
The lines are submerged so that when you pull the piston back, it doesn't suck air back up into the cylinder, rather it pulls fluid.
Once all the air is out, pull the piston back to the rest position which has the ports sealed off.
Then, install.
Pump the MC piston and watch for the air leaving the temp lines in the container.
The lines are submerged so that when you pull the piston back, it doesn't suck air back up into the cylinder, rather it pulls fluid.
Once all the air is out, pull the piston back to the rest position which has the ports sealed off.
Then, install.
If you using the plugs and not them temp lines, then after you have got all the air out of the MC by doing as you stated bolt it back up in the car with the plugs still in it and then get in the car and press the brakes to ensure you have a tight pedal. If not re-bleed is you do then take off the plugs and hook the brake lines up.
Originally Posted by Jditlfm
If you using the plugs and not them temp lines, then after you have got all the air out of the MC by doing as you stated bolt it back up in the car with the plugs still in it and then get in the car and press the brakes to ensure you have a tight pedal. If not re-bleed is you do then take off the plugs and hook the brake lines up.
I'm just not seeing in my mind's eye how doing that way fills the MC up with fluid displacing the air. Does the compressed air leak past the inner seals?
Just curious
