Possible Brake booster issue (1 Viewer)

[RyRoRyan]

Dont have my cruiser with me so I dont have my FSM with me either. However I am pretty sure that I have a booster problem and was going to grab the part on the way home but wanted to confirm with yall first to confirm my suspicions.

• Brakes do work better when engine is running than not. (I can feel the booster giving me SOME help)
• Brakes seem to work fine when pedal is about 1/3 down or less. (Dont know if there is any or much boost helping here or not)
• When more than 1/3 down, the pedal gets much harder to press, very quickly.
• I can pull 17" of vacuum on the tube supplying the booster so I know I have sufficient vacuum.
• If I pull vacuum with the brakes released on the booster itself, I can pull it down to about 19" or so, but it will bleed down to 0 in about 10-15 seconds.
• If I try to pull vacuum while someone is pressing on the pedal, I can get down to about 7" of vacuum and it drops back to 0 within a few seconds of me stop pumping.
• I cannot get the pedal down as far as to lock up the tires...pretty close to this though, as I am comfortable driving it safely.

Do to the above results...primarily the issue of it not holding a vacuum for longer than a few seconds, tells me that I likely have a leak in it. Does this sound accurate?

 

[inkpot]

Tires should not lock up if ABS is operating properly

 

[RyRoRyan]

Tires should not lock up if ABS is operating properly

Let me clarify...I cant get it to stop as such the ABS pump will kick in.

 

[SUMMIT CRUISERS]

The tell tell sign of a bad booster is: If you depress the brake pedal down and you hear a wooosh and the rpm's of the engine drop, the booster is bad. If your hearing is bad, spray some soapy water around where the booster attaches to the firewall on the inside of the cab and depress pedal looking for big bubbles.

If the vacuum doesn't hold in the booster the check valve or grommet at the booster could be bad. Remove and inspect/test.

Couple of tips:
Have you flushed the brake lines with a qt or more of brake fluid?
Have you activated the abs system on a dirt road? This also seems to help.