Under hard braking the pedal will momentarily travel freely and then re-engage. This is rather disturbing as it happens only on those rare occasions that you really want to get to a stop in a hurry. I originally suspected the abs, however, I read that if the abs goes out it would only make you work harder to stop. I now suspect a worn master cyclinder. I have had the vehicle 7 years and routinely inspect and replace brake pads and faulty calipers. The car has 150,000 miles on it and i don’t think it has ever had the master cyclinder replaced. Any thoughts??
You need to see a good mechanic ASAP. Your brake system is failing and it could be your master cylinder or one of several other problems. You may use the brakes and the momentary free travel will be permanent. If this happens…you will not have the ability to stop the truck. Guessing at a mechanical problem is a costly and ineffective way to troubleshoot any vehicle defect.
To check for a worn master cylinder, pump the brake pedal a few times and then hold down the brake pedal. If the brake pedal sinks slowly to the floor it’s an indication of a worn brake master cylinder.
After you get the faulty brake parts replaced (my guess is master cylinder) get the brake fluid changed every 3 years.
That will greatly extend the life of brake components.