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lost brake pressure during bleeding
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trekvana
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Dec 4, 2011, 3:41 PM
Post #1 of 9
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lost brake pressure during bleeding
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Automatic 98 2.2L GMC Sonoma 2WD
So while I was bleeding the rear passenger wheel, I lost brake pressure. The petal was pumping and getting stiff no problem but after a few pumps and bleeds the brakes no longer pump up. They just go down to the floor every time I pump them. The fluid is no longer coming out the reservoir either. If I open up the bleed valve and push the brake pedal to the floor I only get a light trickle of fluid every time. No matter how much I bleed the brakes this way the level of the reservoir stays the same which leads me to believe I'm just pumping out the fluid that is already in the lines. I'm thinking the master cylinder broke? Maybe the seals inside the cylinder went bad? Or possibly the piston inside? Or maybe the master cylinder got clogged up? The brake fluid was pretty much black.
Whatever I do I can't get the brakes to pump up and get stiff
(This post was edited by trekvana on Dec 4, 2011, 3:49 PM)
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Sidom
Veteran
/ Moderator
Dec 4, 2011, 3:49 PM
Post #2 of 9
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Re: lost brake pressure during bleeding
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What did you do to the system that required bleeding????
If you crack the brk lines (one at a time) at the master, do you get fluid out of either line???
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Hammer Time
Ultimate Carjunky
/ Moderator
Dec 4, 2011, 3:57 PM
Post #3 of 9
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Re: lost brake pressure during bleeding
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Also, are you sure the master didn't go dry in one of the compartments?
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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trekvana
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Dec 4, 2011, 3:59 PM
Post #4 of 9
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Re: lost brake pressure during bleeding
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The fluid was real dirty so I just wanted to flush the fluid out. My ABS light is on as well so I figured black fluid is not good to begin with
(This post was edited by trekvana on Dec 4, 2011, 4:00 PM)
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trekvana
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Dec 4, 2011, 4:02 PM
Post #5 of 9
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Re: lost brake pressure during bleeding
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Ill try to crack the lines at the cylinder and take a look.
@Hammer time: How to check if one of the compartments went dry?
(This post was edited by trekvana on Dec 4, 2011, 4:03 PM)
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Hammer Time
Ultimate Carjunky
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Dec 4, 2011, 4:06 PM
Post #6 of 9
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Re: lost brake pressure during bleeding
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If you don't know for sure that you kept the master full, then it probably did go dry and now you have air through the whole system. Keep the master full and keep bleeding. If the fluid was that bad, you could have a bad master now too from bottoming it out during bleeding.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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trekvana
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Dec 4, 2011, 5:10 PM
Post #7 of 9
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Re: lost brake pressure during bleeding
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actually i first siphoned out the bad fluid and then filled the reservoir up with fresh fluid. I never let the fluid get below the low mark the whole time. I did however bleed with the reservoir cap off. Could that have introduced air?
pretty much everything was going fine and then i got this issue. its as if the master doesn't want to suck fluid out of the reservoir. regardless how many times i pump the reservoir doesn't go down
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Discretesignals
Ultimate Carjunky
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Dec 4, 2011, 5:46 PM
Post #8 of 9
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Re: lost brake pressure during bleeding
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If you have ABS, you may need to do an automated bleed routine. Unfortunately it requires an enhanced scan tool.
Procedure for brake bleeding with ABS:
TWO PERSON PROCEDURE
1. Raise the vehicle in order to access the system bleed screws.
2. Bleed the system at the right rear wheel first.
3. Install a clear hose on the bleed screw.
4. Immerse the opposite end of the hose into a container partially filled with clean DOT 3 brake fluid.
5. Open the bleed screw 1/2 to one full turn.
6. Slowly depress the brake pedal. While the pedal is depressed to its full extent, tighten the bleed screw.
7. Release the brake pedal and wait 10-15 seconds for the master cylinder pistons to return to the home position.
8. Repeat the previous steps for the remaining wheels. The brake fluid which is present at each bleed screw should be clean and free of air.
9. This procedure may use more than a pint of fluid per wheel. Check the master cylinder fluid level every four to six strokes of the brake pedal in order to avoid running the system dry.
10. Press the brake pedal firmly and run the Scan Tool Automated Bleed Procedure. Release the brake pedal between each test.
11. Bleed all four wheels again using steps 3-9. This will remove the remaining air from the brake system.
12. Evaluate the feel of the brake pedal before attempting to drive the vehicle.
13. Bleed the system as many times as necessary in order to obtain the appropriate feel of the pedal.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Dec 4, 2011, 5:48 PM)
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Hammer Time
Ultimate Carjunky
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Dec 4, 2011, 6:45 PM
Post #9 of 9
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Re: lost brake pressure during bleeding
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Automated bleeding is not required on this vehicle but you could really benefit from a pressure bleeder. I'm suspecting that since your fluid was in such bad shape that the inside of some of the components may be also, including the master cylinder. It's not unusual for a master cylinder to fail during bleeding because you push the rubber seals deep into the bore into areas that they do not usually travel and rust and cylinder damage builds up which damages the seals.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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