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05-21-2014, 04:39 PM
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#1 |
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Registered User
Join Date: May 2014
Location: Catchall
Posts: 120
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Master cylinder bad?
I got a refurbished master cylinder from O'rielly's a week ago and began to bench bleed it today. I started to pump the MC got all the air out then i noticed the rear reservoir has a constant bubble popping out. It seems its not closing properly.
This master cylinder is faulty right? |
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05-21-2014, 04:49 PM
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#2 |
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Registered User
Join Date: May 2014
Location: Catchall
Posts: 120
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Re: Master cylinder bad?
you can see the bubble forming on the right....
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05-21-2014, 05:53 PM
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#3 |
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Registered User
Join Date: Apr 2004
Location: Las Vegas, NV
Posts: 2,188
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Re: Master cylinder bad?
Even once you are sure you got all the air out, there is likely some more. Bleeding it also causes the big bubbles to break into tiny ones... those may take more time.
Let it sit for an hour or more before bleeding again. I usually do this a few times before bolting it up. Every time I'm surprised by how long they keep bubbling, but eventually they're gone. Double check your block off plugs as well - those little plastic turds dont always want to seal. Make sure to keep the reservoir full enough throughout the process. If the siphon tube gets any air in it, its time to start over.
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RIP EastSideLowLife '72 C20 SWB convert. 5 lug, LS1/4l60e |
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05-21-2014, 06:06 PM
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#4 |
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Registered User
Join Date: May 2014
Location: Catchall
Posts: 120
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Re: Master cylinder bad?
thanks i realized i didnt bleed it enough finally the bubbles stopped.......
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05-21-2014, 06:11 PM
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#5 |
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Registered User
Join Date: May 2014
Location: Catchall
Posts: 120
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Re: Master cylinder bad?
ok here is something wild...
I get the old master cylinder off and look what i find.... I pull a 3 inch cut bolt out... ok what is going on here guys? |
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05-21-2014, 07:55 PM
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#6 |
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Registered User
Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,332
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Re: Master cylinder bad?
Someone lost the original plunger/rod and figured that'd be close enough. I guess if it drove it was. I had to make my own once but I used actual rod, not a bolt, and rounded the nose, and so on.
The original rod (at least in my 3/4t drum truck) looked roughly like that but it was smooth and had a "mushroomed" end on it. If you need photos let me know.
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1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible |
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05-21-2014, 08:04 PM
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#7 | |
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Registered User
Join Date: May 2014
Location: Catchall
Posts: 120
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Re: Master cylinder bad?
Quote:
Is this part readily available? Do i take the booster apart to assemble? Been searching the forum for any info on this but no luck so far.... |
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05-21-2014, 08:16 PM
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#8 |
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Registered User
Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,332
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Re: Master cylinder bad?
Here you go! Looks like the rod tip is adjustable. Normally I'd make that adjustment at the pedal rod on the 72 but this is from a '70 3/4t.
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1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible |
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05-21-2014, 08:29 PM
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#9 |
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Registered User
Join Date: Apr 2004
Location: Las Vegas, NV
Posts: 2,188
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Re: Master cylinder bad?
Yep, someone definitely improvised a new booster rod
 The pushrod is usually supplied with a new booster. I'm not sure of the part number to find one individually. See if a parts store has a booster and try to swing a deal. Otherwise, contact a board vendor
__________________
RIP EastSideLowLife '72 C20 SWB convert. 5 lug, LS1/4l60e |
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05-21-2014, 10:01 PM
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#10 | |
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Registered User
Join Date: May 2014
Location: Catchall
Posts: 120
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Re: Master cylinder bad?
Quote:
Mines a '69 1 ton. Still looking for a replacement. Thinking about calling the chevy dealer tomorrow. |
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