Hi I'm new here and hope to find someone in the know for help with a braking issue. I have a 2000 ss with a 3800 with 134,000 miles. Recently my brake light came on. The husband and myself are "backyard mechanics" and need help because we can't find our manual. I have no fluid in my reservoir, refilled and pumped brakes and fluid is gone again and obviously my pedal goes to floor. I can find no leaks in the lines, at the master cylinder or near the booster. Is there any other part of the braking system particular to this vehicle we are not familiar with that could cause this?

 

So if you are positive there is no leaks visible anywhere then your master cylinder is leaking to the inside of the brake booster, which has two sides to its function. The diaphragm inside it can fill and leak on one side (wet at the bottom of the booster on the outside. Then there is the inside of the diaphragm that is sealed so it can fill up with fluid and not visually leak. There is also the possibility that the front side can fill up and not leak as stated because the engine vacuum is applied to that side and the fluid can be siphoned into the engine vacuum system while the engine is running.


If this is the case then you must change the master cylinder and the brake booster and the booster vacuum check valve all at once and completely bleed the whole system in proper order.