Author Topic: brake bleeding question  (Read 3463 times)

cascadia

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brake bleeding question
« on: April 17, 2010, 00:13:54 »
I'm about to get my barn pagoda fired up for the first time since August of last year.  I'm bleeding the brakes using a miti-vac, have it up on the lift, and when I spin the front tire and push on the brake pedal I'm getting nothing.  Bled the brakes a 2nd time, (starting from the rear right, etc) , still the same result.  The miti-vac makes bubbles of its own so maybe that's not the best tool to use for a good visual read. I have pedal, but no braking action.  My question is whether this is because the brake booster has no vacuum in it?  Haven't started the car yet, that's set for Monday.
Bob in Portland, Oregon.

jeffc280sl

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Re: brake bleeding question
« Reply #1 on: April 17, 2010, 00:57:52 »
The brake booster does not have to be under vacuum to bleed the brakes.  It is a power assist only.  How are you using the Mity Vac?  You need to crack open the bleeder valve ever so slightly to suck brake fluid though the lines.  If you open the valve too much you will not get a good brake fluid suction because you will also be sucking air that leaks in around the bleeder valve.  I have used teflon tape on the bleeder valve to help eliminate this.

ja17

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Re: brake bleeding question
« Reply #2 on: April 17, 2010, 02:02:37 »
Hello,

Sounds like your rubber brake hoses are restricted and fluid cannot pass through.

Joe Alexander
Blacklick, Ohio
1969 Dark Olive 280SL
2002 ML55 AMG (tow vehicle)
2002 SLK32 AMG (350 hp)
1982 300TD Wagon turbo 4spd.
1963 404 Mercedes Unimog (Swedish Army)
1989 flu419 Mercedes Unimog (US Army)
1998 E430
1974 450SLC Rally
1965 220SE Finback

badali

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Re: brake bleeding question
« Reply #3 on: April 17, 2010, 08:24:39 »
Joe,
I just put a new mastercylinder on a few days ago and used the 2 person method.  I noticed the one on the drivers side rear had low flow when the bleeder was opened.  It was the only one that has the original hose so I am going to change it.  The others all looked new.  Today while driving I got a strange vibration from the rear after letting off the brakes so I am guessing that wheel cylinder was sticking from the fluid not flowing back.  Am I correct to assume this.
Brad

1961 220 Sb
1966 230 SL (Sold)
2019 E 450 4 Matic
2022 GLC 300 4 Matic

cascadia

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Re: brake bleeding question
« Reply #4 on: April 17, 2010, 22:05:47 »
I pulled off the master cylinder today, I suspected something was binding up in there, preventing full travel of the pedal.  Was I thought was firm pedal before turned out to be caused by something internally in the master holding things up.  So that explains my 'no brakes' dilemma.  :P
Bob in Portland, Oregon.