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Brake Master Cylinder

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1977MGMidget

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The other day I got in my 77 midget to get the milage because I had to renew my licence plates and I put my foot in a nice puddle of brake fluid. I was in my socks. I checked and the master cylinder was empty. My question is do I rebuild or buy new? The car has very low milage so I would think the leak is from sitting, more than wear.
Ron
 
Ron,
The only way to know what you’re working with is to crack that bad boy open and see what you have to work with! Theirs a hard white plastic collar inside that you’ll have to chisel out not damaging the cylinder wall. Inspect closely the piston, and cylinder wall. If all looks good with no pitting or cylinder wall scuffing then thoroughly clean, lightly hone, then vigorously clean master cylinder. If master cylinder looks good it should take a rebuild if not, time for new one. If you choose to rebuild, a good way to clean the brake reservoir is to get some denatured alcohol and a small container of BB’s plug all the holes and fill halfway with the denature alcohol and pore all the BB’s in and shake vigorously, changing the alcohol several time during the process until everything is clean. Then dump all the BB’s out a final rinse and a blow dry. You’re now ready to install the kit, lube all the rubber seals with brake fluid or assembly lube and install. Then bench bleed prier to installation.

Good Luck!
 
:iagree:
you will also need a long nose snap ring pliers
if you have never done a master cyl this one is not a good one for your first time

hard white plastic collar inside that you’ll have to chisel out not damaging the cylinder wall and the pistion

I do this buy drilling two small hole in the white
collar and and using to 2 small screw in the holes that you drilled to pull it out
 
BUy new, ebay $104 delievered. I never rebuild these things anymore. Not worth my time if it doesn't work out and I find they never do. In my experience, if they leak from bad/cut seals chances are they are too pitted as well. Usually where the seal sits at rest.
 
wow that cheep now ,when I was fixing them in the 90's it was about $250 a pop and $35 for a kit
for $104 get a new one
 
hooey said:
:iagree:
you will also need a long nose snap ring pliers
if you have never done a master cyl this one is not a good one for your first time

hard white plastic collar inside that you’ll have to chisel out not damaging the cylinder wall and the pistion

I do this buy drilling two small hole in the white
collar and and using to 2 small screw in the holes that you drilled to pull it out
Click to expand...

Ditto to all of the above. These are difficult to rebuild, especially if you are a novice to these. In addition to the previous cautions, even if you succeed with all of the above, it will still leak if the forward portion of the piston that passes through the front seal to the outside is scored, scratched or otherwise damaged by your attempts to get it apart. It's almost an absolute certainly without the right tools. I do recommend having these sleeved, even for new ones and the repops don't seem to hold up well beyond about 6 months. For a car that sits for long periods of time, I think it's a must. I have one sleeved unit and one new un-sleeved unit if you are interested. Contact me privately for that and the name of the best guy I know for sleeving master cylinders.

You can check out my disc brake conversion page so see a sample of the workmanship.

https://gerardsgarage.com/Garage/Tech/DbrakeUg.htm
 
I'd replace it, if only for the time, effort and uncertainty of rebuilding. I rebuilt mine a year and half ago, about 3000 miles ago. It's leaking already and I'm not really looking forward to having to pull it again. Spend the extra now and get a good unit and hopefully you'll have to do this job only once.
 
hooey said:
wow that cheep now
Click to expand...

Yep, got one sittin' in the box right in front of me now. Came in last week. Mine's starting to get mushy and I don't like to wait for stuff. When things break; I go in a attic and get what I need. I'm restoring the car one failed part at a time. Looks like my first cycle is up as I'm having to change things I have already replaced once. Yeah, @ $250 I'd try a kit too. Problem is I work on crap all week long. Last thing I want to do at home is have to fix something.....TWICE. Ebay have made some prices raise, however: if it wasn't for the 'bay, m/c's would still be @ 250 or so.
 
I have re-built several, and while the first one was tough, now I know all the tricks and they are easy. Well, not easy, but very doable.

The first trick is to find the longest thinnest pair of needle-nose pliers you can find. Use a grinder to make them even thinner, then use a cut off wheel or hack saw to cut a notch into either side of the very tippy, tip of the pliers. You will use these to remove the circlip ring weeee down inside the MC.

When you get to that gol-durned plastic ring, get out your propane torch and heat the master cylinder until the ring melts. You can then just stick your long needle nose pliers into the melty ring and pull it right out.

Finally, buy the TRW rebuild kit from bpnorthwest.com. It's awesome. The kits VB and Moss sell... not so much.

But if the cheap MCs are any good and you can afford to buy one and you aren't obsessed with rebuilding old junk (like I am) then I say go for new.
 
hooey said:
wow that cheep now ,when I was fixing them in the 90's it was about $250 a pop and $35 for a kit
for $104 get a new one
Click to expand...

Yeah, I recall the $250 cylinders too.

Moss sells their "Gold" repros for $109 now. (I have one in my MGB since last Spring....works fine)

~Click Here~ to see the Moss unit.
 
I just finished rebuilding mine, and I can tell you that it's no walk in the park. In fact, it's leaking a little bit right now.

I'm now faced with purchasing a new one, just to be done with it. Not a job for the uninitiated. Many, many small parts and all must must just right together, in order. Also, lots of ways to screw it up (just ask, I know).

If you have some skill/experience, rebuild it. If not, get a new Moss one.

Good luck, let us know . . . :thumbsup:
 
Thanks for all the help and advice. I went with rebuilding it. I've been a mechanic for 30 years but I work on large trucks not little cars. It WAS a pain in the butt, but it came apart OK and went together OK. I went for a ride after and it even stops. I want to thank everyone again for all your help.
Ron
 
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