I have a 1978 K5 Blazer that does not get driven as much as I'd like. Vehicle sat for 6 months and I cranked it the other day, fired right up with no problems. Drove it around town to get things warmed up, etc. Ten minutes into my journey the car in front of me was stopped at a light and was slow to take off when it changed green. I put my foot on the brake pedal and applied steady pressure. Pedal gave normal resistance and braking was steady until the pedal was about half way down then it went straight to the floor with no resistance. Fortunately the car in front of me had pulled away. At the next light while stopped I pumped the pedal and could replicate the issue. My question is do I have a bad master cylinder, brake booster, both or something else. This vehicle stays garaged at a location other than my home and due to time constraint I did not check brake fluid level in MC or fluid leak around wheels. Thanks!
