I have a 2003 sequoia. Today I was in the drive thru and when I hit the brakes, the pedal was so hard to press. When you press the pedal it hisses at you like an air leak comming from the pedal itself. The brakes dont work that great, even when I put all my weight on the pedal. One thing I have noticed is that when you let the pedal go, it shoots fluid back into the master cylinder resevior, and it shoots it hard. Also I have abs check lights on but nobody can check these kind of codes. I guess you have to have a special scanner for abs systems. My question is: what do you think that it is the, master cylinder or the booster

 

The ABS might not have anything to do with the brake issue unless it so happened to come on at the same time. Then it could possibly be an issue with your abs pump or just as simple as a sensor that lost its magnatism. I have a good feeling it is the booster cause if you hear a hissing noise of any sort that is vacuum leaking from the booster. In turn there is no pressure on the diaphram and it is stiff to push. Also check your vacuum line going to the booster to make sure it is not disconnected or dryrotted.

 

From what ive seen if a Sequoia loses braking system pressure The ABS, Brake, VSC, and trac lights come on. This can be caused by ALOT of things. You really need to bring the car to a Toyota dealer and have them look at it. Thats a very large truck and if it isnt as simple as a disconnected vacuum hose some can be killed by a crash with that thing.

 

+1 on safety

 

There is a way to check for brake booster failure. You can do this by pumping up the brake while the vehicle is off. Once the pedal gets hard keep pressure on your brake pedal and start the vehicle, if the pedal does not go down you have a bad brake booster.