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Author Topic: Maxi brakes failure  (Read 4444 times)
silversport
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« on: November 11, 2010, 05:40:59 PM »

Fired up the old girl (GM 4106) for a nice weekend in the wine country, when one of the back brake chamber sprung a leak. Went to DA Book but I have Maxi's, replace the diaphragm but air is still escaping from the push rod area. With out a schematic I am unsure on how to take the chamber apart ( are there O rings that need replacing?). Has two air hoses, a plastic cover on one side that has inside a self locking nut on a Allen head stud also a retaining clip holding a washer that the stud is going through ( I think this is to manual release the push rod but I am not sure how). There is a bolt on the bottom of the unit. Any help would be appreciated .
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jackhartjr
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« Reply #1 on: November 11, 2010, 06:16:35 PM »

Not trying to alarm you...however if you do not know what you are doing it could KILL you.  Get someone that knows how to handle this. 
Jack
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Jack Hart, CDS
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lostagain
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« Reply #2 on: November 11, 2010, 06:27:35 PM »

I would just get a new one. Your old one is probably rusty. Not worth fixing.

JC
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JC
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« Reply #3 on: November 11, 2010, 06:45:51 PM »

Amen to the other posts, maxi brakes are too dangerous to fool with. New ones are cheap in comparison to your head.
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PD4107-152
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« Reply #4 on: November 11, 2010, 06:52:28 PM »

I concur. If you want to mess with it. Do so after you've had it replaced.  ...Cable
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Sofar Sogood
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« Reply #5 on: November 11, 2010, 07:37:58 PM »

Don't mess with a spring brake without the proper metal box to put it in, or a properly equipped press.

The spring can knock a cement block out of a wall.

You'll never know what hit you, and those who find you will wish they didn't.

happy coaching!
buswarrior
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« Reply #6 on: November 11, 2010, 08:22:07 PM »

I am reminded of my Dad about 40 some odd years ago that tried to 'fix' an old tube type TV.  One second he was on one side of the room with a screwdriver in his hand...the next he was on the ther side of the room...wondering how he got there.  Those brakes can do that too...or worse!
Jack
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Jack Hart, CDS
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« Reply #7 on: November 11, 2010, 08:49:04 PM »

Just analyze how powerful that spring has to be to stop and hold 30-40 thousand pound vehicles.  You really don't want it jumping out at you.
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« Reply #8 on: November 12, 2010, 01:37:39 AM »

are maxis that different from regular spring brakes?  I changed the diaphragms in my spring brakes, no muss no fuss.  You need the  the bolt that holds the spring, you tighten it to capture the spring, take the can apart, change the diaphragm , and put it alll back together.  Sure a spring is a dangerous thing, but it's not that complicated.  Macpherson struts need spring compressors to be taken  apart for rebuild and that is more dangerous as the compressors are installed by the rebuilder.
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jackhartjr
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« Reply #9 on: November 12, 2010, 04:54:29 AM »

ZuZub, it's not that they are difficult...it's that if you mess up, it is REALLY, REALLY, REALLY BAD!  I was just suggesting that our friend that we want to enjoy this hobby for a long time get help the first time. Grin
Jack
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Jack Hart, CDS
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« Reply #10 on: November 12, 2010, 05:04:01 AM »

From my air brake course notes, the spring in a spring brake exerts about 60% of the force of a full brake application.  Say that is 100 psi into a 30 brake can, that is 60% of 3000, or 1800 lbs.  Looking at the diagrams, that's probably a 600 lbs spring compressed 3 inches or something similar, but the 1800 lbs of force is what the problem is.  Even with a caging bolt, that's a lot of kinetic energy waiting to do something to you.  I think of it as working in a 600 volt 3 phase panel, live...  Wouldn't do it on a bet!

Brian
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« Reply #11 on: November 12, 2010, 06:07:57 AM »

I just don't get it.  Brake cans are cheap and by the time you might start thinking of working on them they are obviously old.  They live in a bad place, covered with road salt, grime and often damp.  Why anybody would even think about servicing them is beyond me.  If it made economic sense the commercial guys would be all over it and they clearly aren't.  Look in the back yard at any truck shop and you'll find an oil drum filled with dead air cans.
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R.J.(Bob) Evans
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« Reply #12 on: November 12, 2010, 06:26:47 AM »

Bob, it's my impression that Maxi chambers are very old design, no longer in production and expensive when you find them.  They are smaller than spring brake chambers so swapping to cheap, new, available parts is hard to manage.  5 minutes with google brought up no links to Maxi chambers for sale, or kits for that matter.  Didn't check ebay.

edit: ebay found a single 30/30 maxi chamber for sale at $175.  http://shop.ebay.com/items/?_nkw=maxi+brake+chamber&_sacat=&_ex_kw=&_mPrRngCbx=1&_udlo=&_udhi=&_sop=12&_fpos=&_fspt=1&_sadis=&LH_CAds=

Brian
« Last Edit: November 12, 2010, 06:29:18 AM by bevans6 » Logged

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Joe Camper
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« Reply #13 on: November 13, 2010, 06:12:14 AM »

175 bucks for that chamber on E-Bay??

Kinda pricy we give 48 bucks a piece for them, new, and not piggyback but complete.
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Eagle Andy
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« Reply #14 on: November 13, 2010, 06:26:00 AM »

I have been watching this post as I have looked at mine and found I have Mini Max cans . Iam thinking I am going to change them out to a newer style. Mine are mounted on the engine side of the drive axle so I think Ihave room for the 30/30 . Like Brian I went on line and could not fined anything related to Maxi cans of mini Max cans .
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