Let me start off with a bit of history. I had been having a vacuum issue, door locks mainly, and oil showing up in the line to the intake so I rebuilt the vacuum pump. The diaphragm was worn out and after the rebuild things seemed to improve. the door locks worked for the most part. They still wouldn't open when the Drivers door was unlocked from the outside so I know there must be a leak somewhere. Today though on the way home from work the pedal got really hard like there's no power assist. Worked fine this morning. Got home. Turned off the car. Pumped the pedal a few times and restarted with light pressure on the brake pedal. The pedal dips a bit but still really hard. I take off the line to the booster while the car is running and put my thumb over it. There is vacuum. Oil too. I don't have a fitting that will work on this line for my vacuum gauge so I plug my gauge into the t before the check valve. I only reads 9". So how can I check to see if my booster is bad or if I'm just not making enough vacuum?
Thanks,
john