Brake bleed issue

[Ont240]

2007 lt 5.3
for almost a year i've had intermittent service stabili-track light . Brakes still were working fine as i understand the system just shuts that function off. Lately i had a front caliper (r) not backing off and generating a hot rotor. Determined the one piston was quite sticky so replaced both front calipers with rebuilt. Now after several attempts to bleed all four wheels , the fronts are continually pushing air bubbles and the brake pedal has next to no resistance. even with the engine running the pedal goes nearly to the floor and the front rotors can be turned by hand. No braking effect on the front. The back brakes have resistance at the bottom of the pedal travel. is there something special to bleeding these brakes. I'M doing
LF,RF,RR,LR
IT's like the master cylinder is letting air past the front position. Yet everthing was working well before the caliper change.

Help please on this one!

 

[wjburken]

2007 lt 5.3
for almost a year i've had intermittent service stabili-track light . Brakes still were working fine as i understand the system just shuts that function off. Lately i had a front caliper (r) not backing off and generating a hot rotor. Determined the one piston was quite sticky so replaced both front calipers with rebuilt. Now after several attempts to bleed all four wheels , the fronts are continually pushing air bubbles and the brake pedal has next to no resistance. even with the engine running the pedal goes nearly to the floor and the front rotors can be turned by hand. No braking effect on the front. The back brakes have resistance at the bottom of the pedal travel. is there something special to bleeding these brakes. I'M doing
LF,RF,RR,LR
IT's like the master cylinder is letting air past the front position. Yet everthing was working well before the caliper change.

Help please on this one!

You should start your bleeding sequence with the caliper that is furthest from the master cylinder and work your way closer so RR, LR, RF, LF. You also need to make sure you are not letting the reservoir go empty as your bleeding it. Some folks use vacuum systems to pull the fluid out, some pressurize the reservoir to force fluid along, other, like me, use someones foot on the brake pedal and have them pump it slowly. Make sure you don't go too far with the brake pedal or you can cause some damage. Might put a short piece of 2x4 behind the brake pedal to limit the travel of the pedal while you are doing this. You also want to make sure the brake line going to your caliper is in good shape and doesn't show signs of swelling as this can hinder things.

If you have air in your ABS module, there are a few ways that I have heard of people dealing with this. I have never done this but have read many posts on here from folks who have. One is with a Tech2 or similar tool that puts the ABS module through bleeding sequence. The other is to take your vehicle to a grassy field or a gravel area and drive the vehicle and then slam on the brakes so the ABS kicks in, repeating this a 1/2 dozen times.

 

[Ont240]

How can pushing he pedal to the floor damage the B Master?
The sequence i used was what a tech video was showing on an auto bleed after the abs module was replaced.

I'll try your suggestion again.

 

[Ont240]

no luck. on RR LR RF LF sequence after almost 2 litres of brake fluid
PEDAL IS SOFT AS A SPONGE.
no braking effect on the front.
Anyone else have an idea?
does the ignition key need to be turned on while bleeding?

 

[George B]

Just looking for the obvious but are the front calipers mounted with the bleeders on the top. Not long ago we had a tread go to three pages before we figured out the caliper was upside down and full of air.

 

[Rocket Man]

You might invest in a Motive pressure bleeder and yes make sure the bleeders are on top.
Motive Products 0108 Brake System Power Bleeder For Most Late Model GM Cars and Trucks https://www.amazon.com/dp/B000TK9FE8/ref=cm_sw_r_cp_tau_.Ci1Eb78FAH67

 

[swathdiver]

2007 lt 5.3
for almost a year i've had intermittent service stabili-track light . Brakes still were working fine as i understand the system just shuts that function off. Lately i had a front caliper (r) not backing off and generating a hot rotor. Determined the one piston was quite sticky so replaced both front calipers with rebuilt. Now after several attempts to bleed all four wheels , the fronts are continually pushing air bubbles and the brake pedal has next to no resistance. even with the engine running the pedal goes nearly to the floor and the front rotors can be turned by hand. No braking effect on the front. The back brakes have resistance at the bottom of the pedal travel. is there something special to bleeding these brakes. I'M doing
LF,RF,RR,LR
IT's like the master cylinder is letting air past the front position. Yet everthing was working well before the caliper change.

Help please on this one!

Something is wrong with a brake line and or the master cylinder gave up the ghost. I think the latter. One problem might have been masking another.

If there is air on the ABS side, that needs to be bled with a Tech-2 scan tool.

 

[Fless]

Something is wrong with a brake line and or the master cylinder gave up the ghost. I think the latter.

This is what I was thinking. If the first attempt at bleeding pushed the pedal to the floor, the seals in the MC may have been damaged.

 

[Ont240]

Today we pull the MC and see what it looks like.

 

[Ont240]

bench test OEM Bosch unit:
With the master purged of fluid:
Finger held over furthermost line port and depressing the plunger then releasing the finger one hears that plunger move ahead by the spring pressure as if the rear was getting pedal pressure.
Holding finger over front closest to firewall and depressing there is no pressure on the finger.
Now with fluid in the reservoir, the rear will squirt fluid on each pump.
the front (firewall side ) fluid just runs out all the time. and there is next to no pressure if one holds their finger over that port.
To me I say the front seal must be ???

tried taking apart. After removing the internal c-clip , depressing the plunger and quickly releasing did not let the plunger come out . There is no position screw any where. How does it come apart?

 

[M123]

Many times when problem with air still in the system can be found within the ABS block as mentioned here.
Other times dose the bake hoses acting like a membrane or expending when they are pressurized.
I would look at the hoses in the first step.


I really don't know if I should advice this, if the community think this is bad I remove right away, it's a bit risky and only do this if you know what you are doing!
This following aren't recommending if you are new to breaks and this in some cases can give more problem but if you haven't and tool to force the ABS pump can you bleeding the block by aim for the highest point and bleed it you when pump and car are of. Note brake fluid ruin paint and this can in some cases give more problem if you don't know what you are doing. This should be done without any pressure at the system.

 

[RET423]

Times 2 on the calipers being reversed, your bleed screws must be on the top of the caliper when it is mounted; if they are on the bottom it is not possible to get the air out of the system.

I have a tech 2 but I have found that a normal bleeding procedure with the ABS fuse removed gets all of the air out pretty efficiently.

RR, then LR, then RF, then LF.

That has been accepted bleed procedure on all Left Side Steer vehicles since the invention of hydraulic brakes

With all due respect to YouTube that is

 

[George B]

At this point if you suspect it's bad get a replacement and bench bleed it before you install it. Also, please confirm the correct orientation for the calipers. Helps us rule out possibilities.

 

[Ont240]

Bleeders are up.
New AC delco master on order. Hope to have by the weekend.
Hoses are in good condition. no swelling.
I've done brakes for 40+ years and this one takes the cake.
Still prefer the older systems without without ABS!
Have equipment I can do a vacuum bleed, if no one around

 

[Ont240]

I have a tech 2 but I have found that a normal bleeding procedure with the ABS fuse removed gets all of the air out pretty efficiently.

Which ABS fuse ? Mine has three. #62 heavy duty ABS, #9 ABS2, #64 ABS1

 

[Ont240]

New B Master arrived this morning . AC Delco(Bosch) Oem from amazon.
Bench bled, then installed. Pulled all 3 ABS fuses. Bled system (short pedal pumps) with the aid of a one way valve from an old Kurig. Up and running like a good thing!

Still curious how the master comes apart. Any Ideas? Twist lock? I'm sure the rebuilders know>

 

[kentman]

I always add the Russell speed bleeders to all my vehicles and swap the fluid every 24 months. No brake issues thus far after almost 100K miles. Fingers crossed.

I will be adding new speed bleeders to our sedan in a month or so. It just turned two years old. It is still on lease, but I plan to buy it off lease in a year.