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How to bench bleed a master cylinder #4604262
12/15/17 10:14 AM
12/15/17 10:14 AM
Joined: Jun 2002
Posts: 12,524
The Motor City
Kestas Offline OP
Kestas  Offline OP
Joined: Jun 2002
Posts: 12,524
The Motor City
I need to replace the brake master cylinder on my 2010 Nissan Murano. I already bought the new unit.

The instructions give a choice of bleeding methods. One is to plug the ports and pump the piston until it can't move. The other is to use bleeder tubes that direct the fluid back to the reservoir. What are the pros and cons of each method? I have the plugs for the ports, but I don't have bleeder tubes.


Re: How to bench bleed a master cylinder [Re: Kestas] #4604321
12/15/17 11:07 AM
12/15/17 11:07 AM
Joined: Aug 2017
Posts: 560
MN
14Accent Offline
14Accent  Offline
Joined: Aug 2017
Posts: 560
MN
Either one works. I usually just do the port plug method, then install on the car and have someone pump the pedal while I crack the lines at the master, just like a bleeder screw. Doing it this way I almost never have to bleed at the wheels.


2013 Chevrolet Volt - Saves enough in fuel to pay for itself!

2003 Cadillac Seville STS - The winter "beater", it uses the Volt's fuel
Re: How to bench bleed a master cylinder [Re: Kestas] #4604341
12/15/17 11:25 AM
12/15/17 11:25 AM
Joined: Jun 2009
Posts: 3,699
Chicago, IL
tomcat27 Offline
tomcat27  Offline
Joined: Jun 2009
Posts: 3,699
Chicago, IL
I just finished doing the "port plug" method on the MC for my Cougar. worked well.


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Re: How to bench bleed a master cylinder [Re: Kestas] #4604347
12/15/17 11:29 AM
12/15/17 11:29 AM
Joined: Sep 2012
Posts: 5,384
DFW
DBMaster Offline
DBMaster  Offline
Joined: Sep 2012
Posts: 5,384
DFW
Never tried the port plug method. May have to if there's a next time. My 89 Accord used to go through MCs every 100K miles like clockwork. I replaced the unit three times on that car using the small tubes directed into the reservoir. It worked fine, too.

Re: How to bench bleed a master cylinder [Re: Kestas] #4604412
12/15/17 12:52 PM
12/15/17 12:52 PM
Joined: Jan 2004
Posts: 4,167
California
nthach Online content
nthach  Online Content
Joined: Jan 2004
Posts: 4,167
California
I've done port plug last time I've replaced a MC. Worked fine, not as messy as the tubes.

Re: How to bench bleed a master cylinder [Re: Kestas] #4604421
12/15/17 12:57 PM
12/15/17 12:57 PM
Joined: Jun 2013
Posts: 1,039
iowa
Traction Offline
Traction  Offline
Joined: Jun 2013
Posts: 1,039
iowa
Port method is the easiest, and works. You can also mount the MC and use the brake pedal to bench bleed. The problem with either method is when you go to hook up the lines it runs out, and all over. But, if you hold the brake pedal just halfway down or more with a prop rod, or something, then when the pedal is depressed, it blocks the output ports inside the cylinder bore, and then nothing runs out. You can do the same thing when changing calipers, etc. Makes bleeding much easier too, by not letting all the fluid leak out of the master, and lines. It's like holding water in a drinking straw with your finger. You can hold brake fluid for days in the system using that method, but you would probably want to unhook the battery, because your brake lights will be on is all.


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Re: How to bench bleed a master cylinder [Re: Kestas] #4604476
12/15/17 02:00 PM
12/15/17 02:00 PM
Joined: Jan 2007
Posts: 17,501
Clovis, CA
Merkava_4 Offline
Merkava_4  Offline
Joined: Jan 2007
Posts: 17,501
Clovis, CA
All you do is thread in the little plastic adapters where the brake lines normally go. Then you hook the little clear hoses to the adapters and submerge the other end of the hoses below the brake fluid in the master cylinder. Then you take a #3 Phillips screwdriver and push the piston several times. When the bubbles quit coming out of the hoses, you're done.


Re: How to bench bleed a master cylinder [Re: Kestas] #4604643
12/15/17 04:41 PM
12/15/17 04:41 PM
Joined: Jun 2002
Posts: 12,524
The Motor City
Kestas Offline OP
Kestas  Offline OP
Joined: Jun 2002
Posts: 12,524
The Motor City
Thanks for the feedback. One bonus with this job is that a brake fluid flush was in the queue. By putting it off I will have only needed to do it once.

Re: How to bench bleed a master cylinder [Re: Kestas] #4606551
12/17/17 07:54 PM
12/17/17 07:54 PM
Joined: May 2005
Posts: 2,202
Toronto, Canada
George7941 Offline
George7941  Offline
Joined: May 2005
Posts: 2,202
Toronto, Canada
I have always used the tubes to direct the flow back into the mc and the method works extremely well. I don't see how all the air can be purged if the ports are plugged since any bubble that gets trapped has nowhere to go. If the mc is mounted in the vise with the front inclined down, I can see most of the bubbles, but perhaps not all, escaping through the compensating ports when the outlet ports are plugged.


2006 GMC Sierra 4.3l, NV3500,G80 , Mobil 1 5W30, Dexcool.
1987 BMW R80 - sold
2015 Honda CBR300R

Staying out of the right lane a lot.
Re: How to bench bleed a master cylinder [Re: Traction] #4606555
12/17/17 07:58 PM
12/17/17 07:58 PM
Joined: May 2005
Posts: 2,202
Toronto, Canada
George7941 Offline
George7941  Offline
Joined: May 2005
Posts: 2,202
Toronto, Canada
Originally Posted By: Traction
Port method is the easiest, and works. You can also mount the MC and use the brake pedal to bench bleed. The problem with either method is when you go to hook up the lines it runs out, and all over. But, if you hold the brake pedal just halfway down or more with a prop rod, or something, then when the pedal is depressed, it blocks the output ports inside the cylinder bore, and then nothing runs out. You can do the same thing when changing calipers, etc. Makes bleeding much easier too, by not letting all the fluid leak out of the master, and lines. It's like holding water in a drinking straw with your finger. You can hold brake fluid for days in the system using that method, but you would probably want to unhook the battery, because your brake lights will be on is all.


Holding the pedal halfway down or more does NOT block the output ports. However, holding the pedal down, even if just a bit, blocks the compensating ports and then vacuum will prevent fluid running out. It works well, I can attest to that from experience.


2006 GMC Sierra 4.3l, NV3500,G80 , Mobil 1 5W30, Dexcool.
1987 BMW R80 - sold
2015 Honda CBR300R

Staying out of the right lane a lot.

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