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All Brake Experts Please Read.....


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Been a long time, but a good night... low 60's in the Carolinas, girlfriend working till late and Robin Trower radio on Pandora... so I decided to tear off more engine bay parts getting ready to pull it. Some good news and some bad and a few questions...


o 3 of 4 bolts on the brake booster yielded but that fourth, lower outboard, was a bitch 

   until I figured which wrench type to use and which angle. Then off it came... so basic 

   question? For a '75, should I rebuild the master cylinder and reuse the booster? 


   McCartney in his resto book recommends chucking the old master and just replace it with

   new. Is that the prevailing recommendation? And how about the booster. I read that they are 

   very sturdy and should be OK... I had no issues when I drove the car a few times when I

   bought it. How does one actually validate that the booster is OK and ready to re-use?


o Next topic... removing the brake line nuts from the master cylinder went well.. for 3 out of 5....

    The last two bastards would not budge and eventually stripped. So I just clipped the damn 

    brake lines so I could remove the booster/master.... I probably will just run new lines anyway, 

    but I was curious.. is there such a procedure as "splicing" a new section of brake line into an 

    existing run? I figure there must be a line coupling that can join two flared sections?


OK - thanks for any comments.... I am into 5 years already and have sooooooo much to do. 

Fun at the prospect of all of the projects ahead... but depressing that I want to drive this damn




1975 - 2366762 Born 7/75

See the whole restoration at:


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If the brake system worked fine before why are you considering replacing components? Boosters last a long time, like 30+ years (at least mine has). If it ain't broke don't fix it.


Sure if you have a flare tool you can buy line ends and a union joint but why bother? Brake lines are cheap. If you are concerned about an old brake system (as per master and booster), then go through and replace *all* the hard and soft lines. Not required if no rust, but not that expensive or hard to do, particularly if the engine is out. If you don't already have braided flexible lines then this is a good time to upgrade.


Just my '02 cents. --Fred '69 & '74tii


'74tii (Colorado) track car

'69ti (Black/Red/Yellow) rolling resto track car

'73tii (Fjord....RIP)

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+1 on the advice above re the booster...mine are (knock on wood) both original and both function as they should.  Check the booster for evidence of brake fluid inside it--that would be a very good reason to replace the M/C (see below).


M/C -- so long as it's not original--or very old--and shows no sign of leakage or poor brake performance that can be traced to the M/C, I'd reuse it.


Hopefully the brake lines you clipped are the ones that go to the left front caliper--they're easy to replace.  If they go to any other wheel (esp the rears) you're in for a fun job if you don't find a nearby junction.   And remember, those are "bubble flares", aka "double flares", not the more common single flares.   




'69 Nevada sunroof-Wolfgang-bought new
'73 Sahara sunroof-Ludwig-since '78
'91 Brillantrot 318is sunroof-Georg Friederich 
Fiat Topolini (Benito & Luigi), Renault 4CVs (Anatole, Lucky Pierre, Brigette) & Kermit, the Bugeye Sprite

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Rebuilding the brake master cylinder can be worthwhile with two caveats:  1.  You don't mind spending the time cleaning, disassembling and reassembling the original master cylinder with a complete rebuilt kit.  2.  The inside bore of the master cylinder must be completely free of rust, pitting or other damage, otherwise it has to be tossed.  With master cylinders that are no longer available for some marques, some people have them sleeved.


Reassembling it can be tricky but it's doable if you are patient and have the right tools and some rubber grease.


It's very rewarding when you reinstall it and everything works as it should but for most people who don't want to spend the time or who are not interested in the inner workings of the master cylinder, it's probably better to just buy a new one.


If you do decide to rebuild it, let me know if you need photos, etc...


Regards, Maurice.

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Buy an 11mm hydraulic fitting wrench so you don't strip the nuts taking them off the next time. It looks like a box wrench with a gap cut into it so you can get it over the tubing and down onto the brake line nut. This tool will not round off and strip the nuts like you did taking it off. I usually use it to break the nut loose, then you can use an open end.

Definitely reuse he booster if it holds a vacuum. MC is a tough call. It depends on a lot of things; age, maintenance done, visible leaks on the outside, fluid inside the booster when you take off the MC.

Mike Katsoris CCA#13294                                                

74 InkaGangster 4281862

2016 Porsche Boxster Spyder,    2004 BMW R1150RT,  
76 Estorilblau 2740318                      

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Buy an 11mm hydraulic fitting wrench so you don't strip the nuts taking them off the next time. 

= flare nut wrench, like these, for example: http://www.craftsman.com/wrenches-flare-nut-wrenches/b-1305591

John in VA

'74 tii "Juanita"  '85 535i "Goldie"  '86 535i "M-POSSTR"  

'03 530i "Titan"  '06 330ci "ZHPY"


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Try Bel-Metric for a 10mm union for splicing two brake lines with fittings already on them. They have tees available too. I just bought a tee and a short 10" brake line so I could split the outlet on an E21 master into two lines coming out of the bottom. They have another union for lines without fittings like the on you have pictured as well


Mike Katsoris CCA#13294                                                

74 InkaGangster 4281862

2016 Porsche Boxster Spyder,    2004 BMW R1150RT,  
76 Estorilblau 2740318                      

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