Yesterday i drove my truck for the first time in six weeks and completley lost my braking ability. The pedal went all the way to the floor and my truck hardly even slowed down as I was going 35. I hit the parking brake and nothing happened either. I coasted to a stop on the shoulder and saw that my ABS light was on. I saw that my brake fluid was well below the add line so i filled it back up. After pressing the brakes again there was almost no difference and the fluid level dropped down again. I eventually realized that if i drove under 10 mph i could stop the truck but i had to depress the pedal all the way down and it would very slowly come to a stop. Im sure i have a leak but to my understanding there are two units controlled by the master cylinder to prevent near total brake loss if you have a leak. Does anyone have any idea where it could be coming from that would render the brakes usless over 10mph? Thanks
Sounds like you might have air in your lines. Also, you may have a vacuum line disconnected from your brake system. Check the vacuum lines first, if they are good then I'd suggest bleeding your brakes.
Your parking brakes are mechanical so they have an issue such as a seized cable or parts worn or dislocated. The foot brakes are hydraulic and if you have a leak in the front or rear circuit the pressure differential valve usually shuttles and is locked into that position by the warning light switch. When this occurs the pedal will typically go nearly to the floor to do any braking, either the front or the rear, so the braking is reduced substantially. If your reservoir was empty then you would have air in the system and no brakes, except by pumping several times if you're lucky. Sometimes a reservoir will get to low due to the front brake pad wear as the pistons are displacing the wear of the pads.
losing brake fluid is a definite sign of a leak in your braking system. start by looking under your truck, specifically the inside of your tires and brake backing plates, if you see wetness you probably found your leak. do not do this on a rainy day as water and brake fluid can look alike. also with your truck sitting for 6 weeks, seals at calipers get hard and wheel cylinders if you have rear drum brakes tend to leak after a vehicle has set up for a while
