# No braking pressure **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** gmc, 1500\ **Created:** [July 31, 2020, 1:08am UTC](https://community.cartalk.com/t/no-braking-pressure/168088 "2020-07-31T01:08:07Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![Brock2972](https://avatars.discourse-cdn.com/v4/letter/b/85e7bf/32.png) [@Brock2972](https://community.cartalk.com/u/Brock2972)\ **Post date:** [July 31, 2020, 1:08am UTC](https://community.cartalk.com/t/no-braking-pressure/168088/1 "2020-07-31T01:08:07Z")
The brakes on my truck had become very soft and airy sounding, so my friend offered to fix them. He loosened the bleeders to gravity bleed the truck and left them open too long and all the brake fluid drained out. I filled up the reservoir and bled them properly, but there was no pressure buildup whatsoever. I suspected the master cylinder may have gone bad so I replaced it with a new one and bench bled it before installing. After installing and bleeding there is a tiny bit of pressure, but it’s almost nonexistent. I’m completely at a loss. Any advice would be appreciated. ---
**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\ **Post date:** [July 31, 2020, 1:11am UTC](https://community.cartalk.com/t/no-braking-pressure/168088/2 "2020-07-31T01:11:18Z")
What year? Some ABS systems require a scan tool to properly bleed the brakes when the brake system is opened. Tester ---
**Author:** ![Brock2972](https://avatars.discourse-cdn.com/v4/letter/b/85e7bf/32.png) [@Brock2972](https://community.cartalk.com/u/Brock2972)\ **Post date:** [July 31, 2020, 1:20am UTC](https://community.cartalk.com/t/no-braking-pressure/168088/3 "2020-07-31T01:20:09Z")
1. I’ve heard conflicting statements about that. Most people have told me that it shouldn’t need a scan tool, but there are a few who said I did. ---
**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\ **Post date:** [July 31, 2020, 1:22am UTC](https://community.cartalk.com/t/no-braking-pressure/168088/4 "2020-07-31T01:22:03Z")
> [@Brock2972](#): > > but there are a few who said I did. Those are the people to listen to. Tester ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [July 31, 2020, 1:27am UTC](https://community.cartalk.com/t/no-braking-pressure/168088/5 "2020-07-31T01:27:54Z")
Abs likely. Since mc is new there is either air in system or movement in brake part somewhere. What happened just prior to this? Any work done? How did you bleed system this last time after mc? ---
**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\ **Post date:** [July 31, 2020, 1:32am UTC](https://community.cartalk.com/t/no-braking-pressure/168088/6 "2020-07-31T01:32:43Z")
> [@Brock2972](#): > > and left them open too long and all the brake fluid drained out. > **[Bleeding ABS Brakes: GM Chevy Silverado Vehicles](https://www.tomorrowstechnician.com/service-advisor-abs-bleeding-procedures-for-common-gm-vehicles/)** > > As a rule, the brake circuits on most vehicles with anti-lock brakes can be bled in the usual manner — provided no air has gotten into the ABS modulator assembly Tester ---
**Author:** ![Brock2972](https://avatars.discourse-cdn.com/v4/letter/b/85e7bf/32.png) [@Brock2972](https://community.cartalk.com/u/Brock2972)\ **Post date:** [July 31, 2020, 1:57am UTC](https://community.cartalk.com/t/no-braking-pressure/168088/7 "2020-07-31T01:57:30Z")
There was no work done prior. After installing the new MC, I gravity bled it first, then went to each bleeder and had a buddy pump for me. ---
**Author:** ![Brock2972](https://avatars.discourse-cdn.com/v4/letter/b/85e7bf/32.png) [@Brock2972](https://community.cartalk.com/u/Brock2972)\ **Post date:** [July 31, 2020, 2:00am UTC](https://community.cartalk.com/t/no-braking-pressure/168088/8 "2020-07-31T02:00:42Z")
So the fluid draining completely out let a bunch of air into the modulator? 🥴 ---
**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\ **Post date:** [July 31, 2020, 2:02am UTC](https://community.cartalk.com/t/no-braking-pressure/168088/9 "2020-07-31T02:02:32Z")
Ya think? Tester ---
**Author:** ![COROLLAGUY1](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/corollaguy1/32/7575_2.png) [@COROLLAGUY1](https://community.cartalk.com/u/COROLLAGUY1)\ **Post date:** [July 31, 2020, 2:19pm UTC](https://community.cartalk.com/t/no-braking-pressure/168088/10 "2020-07-31T14:19:35Z")
> [@Brock2972](#): > > The brakes on my truck had become very soft and airy sounding Did the brake warning light came on?If yes,I would check all brake lines since rust could be a problem on a 17 year old truck. After bleeding it,ask someone to press the brake pedal while you look under the vehicule for a leak. Since your vehicule is equipped with drum brakes in the rear, it is difficult to find a leak in this area unless you take out the drum housing.The most common place for a leak is at the wheel cylinder.