Brake problems

hey guys I need help yet again with my 2001 pre runner. I had noticed something was wrong with my brakes they had been giving me this soft feel then a sudden thud like something hitting the brake pedal and my brakes would work fine didn't think much of it. Well this went on for 2months or so then just this week over the course of a few days I noticed all my brake fluid was gone from the reservoir. I found this out in almost the worst way possible but none the less I noticed it my pedal sunk almost all the way down before the thud.

So I took to getting all the wheels off and checking for leaks and found nothing. Traced the lines back and still nothing. Removed the master cylinder and it looked to be in pretty good shape but now leaking a little because compromised seal however I have a new gasket ready to install and hopefully oust that as a diagnosis. My attention is now on the brake booster. Could it be bad? Read up on the symptoms and it sounds more so like I'd have a hard time pushing the pedal before it went totally bad where as I feel I had the opposite. Also would a bad brake booster cause my fluid to disappear? Thanks for any help guys.

 

How many miles are on the master cylinder and the truck?

 

Odometer reads 175k

 

If that is the original MC, then replace it . I recommend OEM (pricey, but isn't your life worth it ?).
Have you followed the brake lines to all 4 corners, looking for leaks? Pull the drums?

 

Yessir followed them all the way down pulled the drums and they're dry. Can't say for sure if it's original mc and brake booster as I bought the truck at 150k about 2yrs ago but I'd assume so

 

What about the LSPV (DS above the rear axle) ? No leaks there?

wild-ass-guess (aka WAG) here:
If you do not have any visible leaks, and are losing fluid, then it might be somehow leaking past a bad MC and into the vacuum chamber of the booster. From there it would be sucked into the intake and into the combustion chambers. Any smoke coming out of the exhaust when applying the brakes?

Also, when you start the truck (with foot pressing on the brake pedal) does the pedal sink toward the floor a bit when the motor catches?

 

Either that or it coming out of the rear of the mc on the floorboard under the carpet. You have to find where the fluid is going 1st. After that you can fix it correctly.

 

Well I hear fluid in the brake booster don't think I'm supposed too...

 

Got the situation resolved problem was the brake booster and mc but now have a new problem in order to get the brake booster in I had to remove the vapor canister got everything put back together and ready to roll I turned the engine on and it seems to idle strange now almost lumpy. Would just fueling it up and driving it off solve the issue? It's throwing a code but can't get to it until later to find out

 

Really nice to know just what code tripped the MIL

I have a code reader in both my vehicles

Did you get the hoses on the correct places ??

Have the vacuum hose hooked up to the booster ?? Bad booster leaking already ??

Sounds like you did not

 

Agree that you have a vacuum leak. Canister and booster are both vacuum driven.

However, since you have a code, it's more likely on the canister side.