# 04 Sonoma slow to stop **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** sonoma, gmc\ **Created:** [November 7, 2019, 2:19am UTC](https://community.cartalk.com/t/04-sonoma-slow-to-stop/152267 "2019-11-07T02:19:29Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Bob-Burnett](https://avatars.discourse-cdn.com/v4/letter/b/46a35a/32.png) [@Bob-Burnett](https://community.cartalk.com/u/Bob-Burnett)\ **Post date:** [November 7, 2019, 2:19am UTC](https://community.cartalk.com/t/04-sonoma-slow-to-stop/152267/1 "2019-11-07T02:19:30Z")
04 GMC is slow to stop like weak brakes …is it the brake booster or calipers or something else ? Thanks ---
**Author:** ![VOLVO-V70](https://avatars.discourse-cdn.com/v4/letter/v/8e8cbc/32.png) [@VOLVO-V70](https://community.cartalk.com/u/VOLVO-V70)\ **Post date:** [November 7, 2019, 2:37am UTC](https://community.cartalk.com/t/04-sonoma-slow-to-stop/152267/2 "2019-11-07T02:37:10Z")
Bob , since you are on the web asking a forum for Brake advice I assume you do not know how to repair a brake system . Therefore you only have one option . Have this thing towed to a brake shop before you have a wreck and injure yourself or someone else. ---
**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:** [November 7, 2019, 2:58am UTC](https://community.cartalk.com/t/04-sonoma-slow-to-stop/152267/3 "2019-11-07T02:58:54Z")
If you have a good firm pedal (i.e. it isn’t sinking to the floor when you press on it), and the stopping performance is always poor, common causes - pads are worn out - rotor is worn out - caliper problem - only one half of the brake system (e.g. rear brakes only) is working - contaminated surfaces on the pads and rotor - faulty power booster This is something a good shop can usually figure out quickly. ---
**Author:** ![db4690](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/db4690/32/2583_2.png) [@db4690](https://community.cartalk.com/u/db4690)\ **Post date:** [November 7, 2019, 3:14am UTC](https://community.cartalk.com/t/04-sonoma-slow-to-stop/152267/4 "2019-11-07T03:14:34Z")
soft pedal? rock hard pedal? ---
**Author:** ![Bob-Burnett](https://avatars.discourse-cdn.com/v4/letter/b/46a35a/32.png) [@Bob-Burnett](https://community.cartalk.com/u/Bob-Burnett)\ **Post date:** [November 12, 2019, 6:26am UTC](https://community.cartalk.com/t/04-sonoma-slow-to-stop/152267/5 "2019-11-12T06:26:53Z")
Its parked in the garage…not driving it Volvo 70 ---
**Author:** ![Bob-Burnett](https://avatars.discourse-cdn.com/v4/letter/b/46a35a/32.png) [@Bob-Burnett](https://community.cartalk.com/u/Bob-Burnett)\ **Post date:** [November 12, 2019, 6:30am UTC](https://community.cartalk.com/t/04-sonoma-slow-to-stop/152267/6 "2019-11-12T06:30:04Z")
It’s my project. I like to work on it and ask dumb ques and after awhile it all comes together…thx ---
**Author:** ![Bob-Burnett](https://avatars.discourse-cdn.com/v4/letter/b/46a35a/32.png) [@Bob-Burnett](https://community.cartalk.com/u/Bob-Burnett)\ **Post date:** [November 12, 2019, 6:32am UTC](https://community.cartalk.com/t/04-sonoma-slow-to-stop/152267/7 "2019-11-12T06:32:39Z")
I’m thi kin the proportioning valve…cuz not gettin fluid to the back brakes…was that on your list? ---
**Author:** ![It\_s-Me](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/it_s-me/32/12660_2.png) [@It\_s-Me](https://community.cartalk.com/u/It_s-Me)\ **Post date:** [November 12, 2019, 6:35am UTC](https://community.cartalk.com/t/04-sonoma-slow-to-stop/152267/8 "2019-11-12T06:35:24Z")
> [@Bob\_Burnett](#): > > I’m thi kin the proportioning valve…cuz not gettin fluid to the back brakes I’m thinking you need a special tool/scanner to bleed them because of the ABS unit. ---
**Author:** ![Bob-Burnett](https://avatars.discourse-cdn.com/v4/letter/b/46a35a/32.png) [@Bob-Burnett](https://community.cartalk.com/u/Bob-Burnett)\ **Post date:** [November 12, 2019, 6:36am UTC](https://community.cartalk.com/t/04-sonoma-slow-to-stop/152267/9 "2019-11-12T06:36:13Z")
Soft but pumps up to rock hard then goes to floor after you start it… ---
**Author:** ![Bob-Burnett](https://avatars.discourse-cdn.com/v4/letter/b/46a35a/32.png) [@Bob-Burnett](https://community.cartalk.com/u/Bob-Burnett)\ **Post date:** [November 12, 2019, 6:38am UTC](https://community.cartalk.com/t/04-sonoma-slow-to-stop/152267/10 "2019-11-12T06:38:56Z")
Yea me too. Ebay or Amazon abt 200$ with autobleed… ---
**Author:** ![Scrapyard-John](https://avatars.discourse-cdn.com/v4/letter/s/f6c823/32.png) [@Scrapyard-John](https://community.cartalk.com/u/Scrapyard-John)\ **Post date:** [November 12, 2019, 5:57pm UTC](https://community.cartalk.com/t/04-sonoma-slow-to-stop/152267/11 "2019-11-12T17:57:51Z")
Obvious question, but does the master cylinder have fluid? Is the brake system (hard lines etc) leaking fluid anywhere? ---
**Author:** ![db4690](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/db4690/32/2583_2.png) [@db4690](https://community.cartalk.com/u/db4690)\ **Post date:** [November 13, 2019, 12:35am UTC](https://community.cartalk.com/t/04-sonoma-slow-to-stop/152267/12 "2019-11-13T00:35:45Z")
sounds like the brake booster is working, for what it’s worth But it definitely appears you have a problem with the hydraulic part of your brakes . . . air in the system, bad master cylinder, something like that So please answer this next question . . . When you’re sitting at a stop light in “D” and your foot on the brake pedal, does it slowly sink to the floor? ---
**Author:** ![Bob-Burnett](https://avatars.discourse-cdn.com/v4/letter/b/46a35a/32.png) [@Bob-Burnett](https://community.cartalk.com/u/Bob-Burnett)\ **Post date:** [November 13, 2019, 8:58pm UTC](https://community.cartalk.com/t/04-sonoma-slow-to-stop/152267/13 "2019-11-13T20:58:22Z")
Havnt driven this trk in 2 years however dont recall that happening…a little history…my son in law bled the brakes said were spongy…then now fluid is not present to rear…so I’m thinkin its prop valve…may try to bypass it on rear only…also why couldnt I unscrew that little reset switch at the end of the valve pull it out and stick something like a pick in there and push it back to it’s normal position? ---
**Author:** ![Bob-Burnett](https://avatars.discourse-cdn.com/v4/letter/b/46a35a/32.png) [@Bob-Burnett](https://community.cartalk.com/u/Bob-Burnett)\ **Post date:** [November 13, 2019, 9:01pm UTC](https://community.cartalk.com/t/04-sonoma-slow-to-stop/152267/14 "2019-11-13T21:01:11Z")
Gonna bypass prop valve on tear brake line and jump from m cyl to rear line with tubing …maybe can get some fluid in rear lines. ---
**Author:** ![Mustangman](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/mustangman/32/44130_2.png) [@Mustangman](https://community.cartalk.com/u/Mustangman)\ **Post date:** [November 13, 2019, 9:24pm UTC](https://community.cartalk.com/t/04-sonoma-slow-to-stop/152267/15 "2019-11-13T21:24:00Z")
If you bypass the prop valve permanently, the rear brakes will lock long before the fronts and cause you to spin. Don’t do that permanenly. Have you checked to see if you have fluid at the combo valve? Then the ABS unit? Have you cracked the brake hose connection at the caliper? Keep in mind, bleed screws can easily corrode up the holes solid. Try removing the entire bleed screw and see if fluid comes out. If it does, the screw itself is clogged. ---
**Author:** ![Scrapyard-John](https://avatars.discourse-cdn.com/v4/letter/s/f6c823/32.png) [@Scrapyard-John](https://community.cartalk.com/u/Scrapyard-John)\ **Post date:** [November 13, 2019, 11:42pm UTC](https://community.cartalk.com/t/04-sonoma-slow-to-stop/152267/16 "2019-11-13T23:42:12Z")
Agree that bleeder valves could be, and most likely are, corroded / plugged. I’ve never had issues with the proportioning valve or the ABS unit (regarding bleeding) on this year model truck cause me issues, despite supposedly needing a scan tool to bleed. Usually, it’s something simple. ---
**Author:** ![Bob-Burnett](https://avatars.discourse-cdn.com/v4/letter/b/46a35a/32.png) [@Bob-Burnett](https://community.cartalk.com/u/Bob-Burnett)\ **Post date:** [November 14, 2019, 12:09am UTC](https://community.cartalk.com/t/04-sonoma-slow-to-stop/152267/17 "2019-11-14T00:09:30Z")
Yep it’s at both lines from master cylinder…it flows well from the prop valve(front brakes only).Just a very small drop or 2 from prop valve rear brake. ---
**Author:** ![Bob-Burnett](https://avatars.discourse-cdn.com/v4/letter/b/46a35a/32.png) [@Bob-Burnett](https://community.cartalk.com/u/Bob-Burnett)\ **Post date:** [November 14, 2019, 12:11am UTC](https://community.cartalk.com/t/04-sonoma-slow-to-stop/152267/18 "2019-11-14T00:11:32Z")
Both front calip bleed ok… ---
**Author:** ![Bob-Burnett](https://avatars.discourse-cdn.com/v4/letter/b/46a35a/32.png) [@Bob-Burnett](https://community.cartalk.com/u/Bob-Burnett)\ **Post date:** [November 14, 2019, 12:14am UTC](https://community.cartalk.com/t/04-sonoma-slow-to-stop/152267/19 "2019-11-14T00:14:20Z")
I separated the single line going to back rear at a little block by the differential and it was bone dry. ---
**Author:** ![Bob-Burnett](https://avatars.discourse-cdn.com/v4/letter/b/46a35a/32.png) [@Bob-Burnett](https://community.cartalk.com/u/Bob-Burnett)\ **Post date:** [November 14, 2019, 12:18am UTC](https://community.cartalk.com/t/04-sonoma-slow-to-stop/152267/20 "2019-11-14T00:18:14Z")
Could I put an inline valve on the back brake line…like the original prop for front and an inline valve for back…I dont know if it would be a metering valve or what its called. [Next page](https://community.cartalk.com/t/04-sonoma-slow-to-stop/152267.md?page=2)