Brake Master cylinder unresponsive

Technical and Repair Discussions

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PostPosted: Sun Jul 15, 2018 3:57 pm
Bleeding the brakes today on my Gen 2 - everything goes fine on the fronts, but when I get to the rear, crack the first bleeder screw nothing comes out. I try a couple more times, and still nothing comes out. Go inspect the rear master cylinder, and I find that the piston moves freely by hand and doesn’t seem to be connected to the internals of the cylinder anymore. Plus, the brake light is on full time. Nonetheless the rear brakes are not clamping and the rotors still spin freely. Do I need to replace the master cylinder? Is there a seal inside that needs to be replaced? Piston no longer seems to be connected to anything. Appreciate everyone’s help-I’m still pretty new to the spec racer game and figuring this car out. Like I said it is a Gen2 and the master cylinder is a girling if that matters

Thanks - Adam

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PostPosted: Sun Jul 15, 2018 5:00 pm
FYI pulled back the seal at the end of the MC where the piston goes in and where there should be a load of grease (as evidenced in the front master cylinder) there is not any grease. It is all dried up. Don’t know if that matters
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PostPosted: Mon Jul 16, 2018 8:43 pm
Not knowing the age of your master cylinders, I would recommend rebuilding them. I have rebuilt Girling master cylinders since the 1970s when I owned Triumphs. Rebuild kits can be purchased from The Roadster Factory (part GISP 1967,if your master cylinder is 3/4”). Mine is on my SRF. Pegasus Racing has the same kits also and excellent rebuild instructions on pdf format.
Again not knowing your situation, I’d rebuild each brake caliper also. Hopefully you have the serrated steel pistons in them. Rebuild kits available from your CSR. The pistons can be a challenge to remove. I use compressed air (carefully!) after I drain the brake fluid. I use a a piece of wood or aluminum bar to “catch”the piston as it comes out under pressure. Be careful if you have not done this before.
Good luck!
Mark Fick

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PostPosted: Mon Jul 16, 2018 9:54 pm
Thanks for your help Mark - I figured out that was the likely problem and went ahead and ordered the MC rebuild kits from Pegasus today - saw the instructions and looks straightforward - hoping it doesn't suck up too many hours!

I haven't rebuilt the calipers on these (but have done caliper rebuilds before) but it's on the to do list.

One more question - any idea what size the caliper bleeder screws are? Screwed one up and need to replace it too.

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