I did a complete replacement of all my brake parts (master cylinder, calipers, rotors & pads). I bled out all the old fluid and filled the system with new. Everything was great for about a week when suddenly there was no pedal. I found fluid dripping under the ABS pump. There was no obvious source of the leak. All the line fittings were tight. I had my son pump the pedal a couple of times and fluid squished out from a black plastic quarter sized plug directly under the left rear line connection. I removed the plug and there was a small brass fitting with a hole in the middle. When the pedal was pumped again, fluid sprayed out.

Can anyone tell me what is causing this leak?

Thanks,

Jeff

why would you replace the master cylinder? just curious.