For last couple of weeks I am having a problem in my Vitz 2004 running only on petrol. The brake works fine most of the time but sometimes while driving when I press the brake pedal, it feels very light and brake doesn't respond timely like it does normally and naturally my foot presses the pedal little more and then suddenly it feels the wheels are jammed and car halts for a while and as a result I almost fall on steering. As soon as I lift my foot from pedal car resumes it motion as normal. This unusual braking hurts as it shakes your body badly for a while and a couple of times because of sudden stalling of car, the motorcycle hit car from back. I need to know what's wrong with brake system, why does it behaves abnormally sometime, any idea how to fix it?
The frequency of happening of the said issue is increasing with passing of each day and some times the issue happens continuously for some time.
Another thing is when I press brake pedal it gives "shoop shoop" sound not sure what does mean.