Checking for vacuum leaks


Was out driving the Chevelle today when I noticed that the brake pedal would sometimes start to loosen up and go further down towards the floor while sitting at a stop sign or light. The pedal would return to normal after I let off of it then pushed it again. The pedal had made it to the floor at one light, the car lurched forward a bit and I threw it into Park to avoid rear ending a guy(thankfully I don’t sit too close behind anyone at stoplights). The pedal wouldn’t always loosen up, just if it was stopped at a light for about a minute.

I am hoping this is a vacuum leak and not something more serious. What kind of tools would I need to check for a vacuum leak?


Nope. It’s not a vacuum leak. It’s the brake master cylinder leaking internally, under pressure. Replacement of the brake master cylinder is the usual remedy, today.


I agree. The master cylinder is failing. Replace it.


well, I guess this is a sign for me to upgrade the car to power disc brakes. I just hope there wasn’t too much damage done to the tranny when I put it in park as the car was trying to move forward(gears were grinding, almost sounded like someone missed a gear with a stick shift when I did it).