I replaced the calipers, rotors, and pads on a 2007 Pontiac Grand Prix. I'm trying to bleed the brakes and I'm having trouble. I've got a Mityvac brake bleeder and I'm starting on the passenger side rear and I'm not drawing any fluid from the master cylinder brake reservoir. I'm wondering why. Can anyone help?

  • 1
    This is totally something that you should be able to do on your own, especially with a Mityvac. Are you sure that you've opened the bleed nipple enough to allow fluid out and that you've got fluid in the master cylinder reservoir?
    – dlu
    Dec 18, 2016 at 21:59
  • 2
    Are you getting anything out? I mean, is air coming out? Is the fluid level going down in your master cylinder? Dec 18, 2016 at 23:27
  • Yeah when I bleed the front driver side brake, it bled fine. Then I went to the rear driver side I can't get anything. I replace vet caliper and the other rear caliper. All I get is a steady line of bubbles nothing sporadic so I think it's just coming from around the bleeder valve. So I spread grease around the bleeder valve and cracked the bolt and it held 15 psi for probably 60 seconds and then finally started leaking air again so it's not pulling air out of the line
    – Ams
    Dec 19, 2016 at 1:26
  • did you ever solve this problem? I now have the same problem with my Mazda 3. It has two hyrdaulic circuits.. the RR ( right rear) and the LF ( left front) are on one and the LR ( left rear) and the RF ( right front ) are on the other., I was able to bleed one set the LR RF combo, but when I try the RR - LF combo there is almost no fluid coming out of either of the brake bleeder valves. I tried using a Vacuum bleeder tool and verified it hold pressure, then when I open the bleeder value I get a little more than a miniscule trickle. For the most part I may have got 1 1/2 oz of fluid from the RR
    – chris
    Dec 27, 2018 at 1:22

2 Answers 2


Is the car on the floor? Many vehicles, I'm not sure if yours does for certain, feature a brake bias apportioning valve which is essentially a "tap" which opens or closes depending on the position of the rear beam axle. If the car is heavily loaded (i.e. has people in the rear seats and a boot / trunk full of cargo), more braking force is sent to the rear wheels.

Problems can occur if you try and bleed brakes with the car jacked up and the rear wheels not touching the ground as this system can be tricked into thinking there is no load on the rear at all thus shutting off the rear brake circuit.

Another possibility is that the car needs to be plugged into a diagnostic computer to tell it that it's brakes are being bled in order to open the ABS lines. However, as you say you bled the front without issue, I suspect the bias valve.

  • Steve Mattews, i have the car jacked up and blocked on all 4 corners with no wheels on so you may be onto something. It would be very difficult to bleed the breaks with the wheels on. But I suppose I could put all of the rotors on with the Lugnuts and block Under the rotors so that the suspension had weight on it and then try to Bleed It That Way. What do you think about tying this? Would this alleviate the problem with the bias valve?
    – Ams
    Dec 19, 2016 at 11:19
  • 1
    Do you suppose this could be possible with the car turned off? In the Haynes manual i have it talks about proportioning valves and how they can apply more braking pressure to the front than the rear due to the fact that the rear of the car can be lighter and not require as much breaking force.
    – Ams
    Dec 19, 2016 at 11:25
  • Does this bias valve or proportioning valve work electronically or manually? What I mean is could it detect no weight on the rear suspension with the car being shut off??
    – Ams
    Dec 19, 2016 at 12:00
  • 1
    Typically it's a spring and lever arm attached to the rear suspension physically so it is doesn't depend on the cars electrical system at all. Dec 19, 2016 at 12:03
  • 2
    You could potentially jack the rear rotors to lift the rear wheels a little? Dec 19, 2016 at 12:04

Bleeding the brakes is a 2 person job. One to open and close the valve at the caliper and another stepping on the brake pedal to force the fluid out.

  • 3
    Doesn't the Mityvac let you pull fluid down to the caliper?
    – dlu
    Dec 18, 2016 at 22:27
  • I just bled the driver side front. It bled fine and the level in the master cylinder reservoir dropped. I went directly to the driver side rear brake. Because that's the order you're supposed to bleed the brakes in. All I could get was air. So I pumped the vacuum pump to 15 psi and smeared Greece all around the bleeder valve. When I cracked it open I didn't get any air like I had and the vacuum pressure stayed at 15. That tells me the only air I was pulling was from around the bleeder valve. Something with the ABS or the master cylinder is not allowing fluid to be pulled to the rear brake.
    – Ams
    Dec 19, 2016 at 1:21
  • And yes the Mighty Vac allows you to pull fluid from the master cylinder reservoir to the brake caliper and bleed the air in that fashion. It should be working fine I just don't know why it won't allow the vacuum to pull fluid from the reservoir to the rear brakes. That's what I replaced on the car was the rear calipers brake pads and rotors
    – Ams
    Dec 19, 2016 at 1:22
  • "Bleeding brakes is a 2 person job" - I bleed my brakes by myself - surgical tubing, bucket, gravity feed and a beer.
    – 3Dave
    Dec 19, 2016 at 16:14

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