# Checking for vacuum leaks

**URL:** <https://community.cartalk.com/t/checking-for-vacuum-leaks/7132>\
**Category:** Maintenance/Repairs\
**Created:** [November 10, 2007, 10:43pm UTC](https://community.cartalk.com/t/checking-for-vacuum-leaks/7132 "2007-11-10T22:43:37Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![bscar](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/bscar/32/34_2.png) [@bscar](https://community.cartalk.com/u/bscar)\
**Post date:** [November 10, 2007, 10:43pm UTC](https://community.cartalk.com/t/checking-for-vacuum-leaks/7132/1 "2007-11-10T22:43:37Z")

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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?

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**Author:** ![hellokit](https://avatars.discourse-cdn.com/v4/letter/h/6a8cbe/32.png) [@hellokit](https://community.cartalk.com/u/hellokit)\
**Post date:** [November 10, 2007, 11:53pm UTC](https://community.cartalk.com/t/checking-for-vacuum-leaks/7132/2 "2007-11-10T23:53:18Z")

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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.

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**Author:** ![willey](https://avatars.discourse-cdn.com/v4/letter/w/a9adbd/32.png) [@willey](https://community.cartalk.com/u/willey)\
**Post date:** [November 11, 2007, 3:12am UTC](https://community.cartalk.com/t/checking-for-vacuum-leaks/7132/3 "2007-11-11T03:12:14Z")

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

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**Author:** ![bscar](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/bscar/32/34_2.png) [@bscar](https://community.cartalk.com/u/bscar)\
**Post date:** [November 11, 2007, 3:37am UTC](https://community.cartalk.com/t/checking-for-vacuum-leaks/7132/4 "2007-11-11T03:37:31Z")

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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).