2005 Yukon brake bleeding

[Blue85]

I'm looking for ideas on how to get fluid to the left rear caliper (Oh, and venting!). A couple of years ago it blew a brake line, so I got the Dorman whole vehicle stainless kit. It was enough of a pain that I only replaced the lines from the ABS unit forward. Bleeding it was a pain, but I was eventually able to get enough pedal to go on the gravel, activate the ABS, bleed some more and repeat (I don't have a bidirectional scan tool). Recently a rear line gave it up, so I replaced both hardlines from the ABS unit (underneath the floor) to above the rear axle. It was a pain since this vehicle is very high mileage and very rusty (and all of the lines are so close to each other and the floor you can't get tools up there, but I digress). I've been putzing with it for probably a month now, sometimes just getting one fitting a day (or less).

I bled the right rear using a vacuum pump and mason jar setup. I had to cycle the pump on and off dozens of times. It spurts a little foamy fluid and then a big air burb. With the pump off, the air gurgled in the lines, but less each time, until clear fluid came out. On the left side, the line holds a vacuum. I disconnected the caliper flex and the frame-axle flex and they are open to both pressure and vacuum. Disconnecting that line from the ABS unit lets fluid drip out. I can put pressure on the bleeder and air bubbles all the way through and out the master cylinder. After that, it still holds a vacuum. I bought another MC cap and installed a fitting on it to pressurize the reservoir. This does not push fluid out of the bleeder, even with pressure at one end and vacuum at the other.

What to do next? Is the ABS module acting like a check-valve because there's so much air?
-build a setup to push fluid from the bleeder screw forward?
-Pull the line from the ABS module and look for dirt or rust at the fitting?
-Give up and replace the ABS module?
-Borrow a scan tool that cycles the ABS?

 

[Truckman4life]

I went with a regular 2005 GMC Yukon/Denali 4wd. I'm assuming it's the same whether it's an XL or 1500 or 2500.

Looks like a complicated one that definitely requires a scan tool according to AllData. There are 2 different procedures depending on if it has JL4 brakes or not. You have to do the scan tool bleeding procedures then you bleed the brakes like normal after that.

ABS Automated Bleed Procedure (w/o JL4)

Notice: When adding fluid to the brake master cylinder reservoir, use only Delco Supreme 11(R), GM P/N 12377967 (Canadian P/N 992667), or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container. The use of any type of fluid other than the recommended type of brake fluid, may cause contamination which could result in damage to the internal rubber seals and/or rubber linings of hydraulic brake system components.

Notice: Refer to Brake Fluid Effects on Paint and Electrical Components Notice in Service Precautions.

Important: This procedure may be performed on all vehicles EXCEPT those equipped with option code JL4, Vehicle Stability Enhancement System (VSES).

Important: The base hydraulic brake system must be bled before performing this automated bleeding procedure. If you have not yet performed the base hydraulic brake system bleeding procedure, refer to Hydraulic Brake System Bleeding (Manual) Hydraulic Brake System Bleeding (Pressure) in Hydraulic Brakes before proceeding.

1. Install a scan tool to the vehicle.
2. Start the engine and allow the engine to idle.
3. Depress the brake pedal firmly and maintain steady pressure on the pedal.
4. Using the scan tool, begin the automated bleed procedure.
5. Follow the instructions on the scan tool to complete the automated bleed procedure. Release the brake pedal between each test sequence.
6. Turn the ignition OFF.
7. Remove the scan tool from the vehicle.
8. Fill the brake master cylinder reservoir to the maximum-fill level with Delco Supreme 11(R), GM P/N 12377967 (Canadian P/N 992667), or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container.
9. Bleed the hydraulic brake system.
10. With the ignition OFF, apply the brakes 3-5 times, or until the brake pedal becomes firm, in order to deplete the brake booster power reserve.
11. Slowly depress and release the brake pedal. Observe the feel of the brake pedal.
12. If the brake pedal feels spongy, repeat the automated bleeding procedure. If the brake pedal still feels spongy after repeating the automated bleeding procedure inspect the brake system for external leaks. Refer to Brake System External Leak Inspection in Hydraulic Brakes.
13. Turn the ignition key ON, with the engine OFF; check to see if the brake system warning lamp remains illuminated.
14. If the brake system warning lamp remains illuminated, DO NOT allow the vehicle to be driven until it is diagnosed and repaired.
15. Drive the vehicle to exceed 13 kph (8 mph) to allow ABS initialization to occur. Observe brake pedal feel.
16. If the brake pedal feels spongy, repeat the automated bleeding procedure until a firm brake pedal is obtained.


ABS Automated Bleed Procedure (W/JL4)

Notice: When adding fluid to the brake master cylinder reservoir, use only Delco Supreme 11(R), GM P/N 12377967 (Canadian P/N 992667), or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container. The use of any type of fluid other than the recommended type of brake fluid, may cause contamination which could result in damage to the internal rubber seals and/or rubber linings of hydraulic brake system components.

Notice: Refer to Brake Fluid Effects on Paint and Electrical Components Notice in Service Precautions.

Important: The following procedures may be performed on vehicles equipped with option code JL4, Vehicle Stability Enhancement System (VSES).

Pre-charge Bleed
The Pre-charge bleed procedure is to be performed when air may have been introduced into the precharge pump inlet hose, the precharge pump or the combination valve. Perform the procedure as follows.

Important: If the brake system warning lamp is illuminated, DO NOT allow the vehicle to be driven until the concern is diagnosed and repaired.

1. Ensure that the master cylinder reservoir is filled to at least the minimum-fill level with Delco Supreme 11, GM P/N 12377967 (Canadian P/N 992667), or equivalent DOT 3 brake fluid from a clean, sealed container.
2. Ensure the master cylinder reservoir cap is ON securely.
3. Install a scan tool.
4. Turn ON the ignition.
5. Select the VSES Special Functions menu on the scan tool.
6. Select Pre-charge Bleed.
7. Press the On key. The precharge pump runs for approximately 3 seconds, circulating fluid from the master cylinder fluid reservoir, through the precharge pump and combination valve, then back to the master cylinder.
8. Evaluate the feel of the brake pedal. If the pedal feels spongy, perform a base brake system bleed.
9. Ensure that the master cylinder reservoir is filled to at least the minimum-fill level with Delco Supreme 11, GM P/N 12377967 (Canadian P/N 992667), or equivalent DOT 3 brake fluid from a clean, sealed container.

Automated Bleed
The Automated Bleed procedure is to be performed when the brake pressure modulator valve (BPMV) is replaced. Perform the procedure as follows.

Important: The base brake system must be bled before proceeding.

Important: If the brake system warning lamp is illuminated, DO NOT allow the vehicle to be driven until the concern is diagnosed and repaired.

1. Ensure that the master cylinder reservoir is filled to at least the minimum-fill level with Delco Supreme 11, GM P/N 12377967 (Canadian P/N 992667), or equivalent DOT 3 brake fluid from a clean, sealed container.
2. Ensure the master cylinder reservoir cap is ON securely.
3. Install a scan tool.
4. Turn ON the ignition.
5. Select the VSES Special Functions menu on the scan tool.
6. Select Pre-charge Bleed.
7. Press the On key. The precharge pump runs for approximately 3 seconds, circulating fluid from the master cylinder fluid reservoir, through the precharge pump and combination valve, then back to the master cylinder.
8. Select Automated Bleed.
9. Press the On key. The precharge pump and ABS pump run for approximately 6 seconds while air is purged from the BPMV.
10. Ensure that the master cylinder reservoir is filled to at least the minimum-fill level with Delco Supreme 11, GM P/N 12377967 (Canadian P/N 992667), or equivalent DOT 3 brake fluid from a clean, sealed container.
11. Perform a base brake system bleed.
12. Evaluate the feel of the brake pedal. If the pedal feels spongy, repeat steps 1-11. If the pedal feel is acceptable, proceed to the next step.
13. Ensure that the master cylinder reservoir is filled to at least the minimum-fill level with Delco Supreme 11, GM P/N 12377967 (Canadian P/N 992667), or equivalent DOT 3 brake fluid from a clean, sealed container.



Hydraulic Brake System Bleeding (Manual)

Caution: Refer to Brake Fluid Irritant in Service Precautions.

Notice: Refer to Brake Fluid Effects on Paint and Electrical Components in Service Precautions.

Notice: When adding fluid to the brake master cylinder reservoir, use only Delco Supreme 11, GM P/N 12377967 (Canadian P/N 992667), or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container. The use of any type of fluid other than the recommended type of brake fluid, may cause contamination which could result in damage to the internal rubber seals and/or rubber linings of hydraulic brake system components.

1. Place a clean shop cloth beneath the brake master cylinder to prevent brake fluid spills.
2. With the ignition OFF and the brakes cool, apply the brakes 3-5 times, or until the brake pedal effort increases significantly, in order to deplete the brake booster power reserve.
3. If you have performed a brake master cylinder bench bleeding on this vehicle, or if you disconnected the brake pipes from the master cylinder, you must perform the following steps:
3.1. Ensure that the brake master cylinder reservoir is full to the maximum-fill level. If necessary add Delco Supreme 11, GM P/N 12377967 (Canadian P/N 992667), or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container.
If removal of the reservoir cap and diaphragm is necessary. clean the outside of the reservoir on and around the cap prior to removal.
3.2. With the rear brake pipe installed securely to the master cylinder, loosen and separate the front brake pipe from the front port of the brake master cylinder.
3.3. Allow a small amount of brake fluid to gravity bleed from the open port of the master cylinder.
3.4. Reconnect the brake pipe to the master cylinder port and tighten securely.
3.5. Have an assistant slowly depress the brake pedal fully and maintain steady pressure on the pedal.
3.6. Loosen the same brake pipe to purge air from the open port of the master cylinder.
3.7. Tighten the brake pipe, then have the assistant slowly release the brake pedal.
3.8. Wait 15 seconds, then repeat steps 3.3-3.7 until all air is purged from the same port of the master cylinder.
3.9. With the front brake pipe installed securely to the master cylinder - after all air has been purged from the front port of the master cylinder-loosen and separate the rear brake pipe from the master cylinder. then repeat steps 3.3-3.8.
3.10. After completing the final master cylinder port bleeding procedure, ensure that both of the brake pipe-to-master cylinder fittings are properly tightened.
4. Fill the brake master cylinder reservoir with Delco Supreme 11, GM P/N 12377967 (Canadian P/N 392667), or equivalent DOT 3 brake fluid from a clean. sealed brake fluid container. Ensure that the brake master cylinder reservoir remains at least half-full during this bleeding procedure. Add fluid as needed to maintain the proper level.
Clean the outside of the reservoir on and around the reservoir cap prior to removing the cap and diaphragm.
5. Install a proper box-end wrench onto the RIGHT REAR wheel hydraulic circuit bleeder valve.
6. Install a transparent hose over the end of the bleeder valve.
7. Submerge the open end of the transparent hose into a transparent container partially filled with Delco Supreme 11, GM P/N 12377967 (Canadian P/N 992667), or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container.
8. Have an assistant slowly depress the brake pedal fully and maintain steady pressure on the pedal.
9. Loosen the bleeder valve to purge air from the wheel hydraulic circuit.
10. Tighten the bleeder valve, then have the assistant slowly release the brake pedal.
11. Wait 15 seconds, then repeat steps 8-10 until all air is purged from the same wheel hydraulic circuit.
12. With the right rear wheel hydraulic circuit bleeder valve tightened securely - after all air has been purged from the right rear hydraulic circuit - install a proper box-end wrench onto the LEFT REAR wheel hydraulic circuit bleeder valve.
13. Install a transparent hose over the end of the bleeder valve, then repeat steps 7-11.
14. With the left rear wheel hydraulic circuit bleeder valve tightened securely - after ail air has been purged from the left rear hydraulic circuit - install a proper box-end wrench onto the RIGHT FRONT wheel hydraulic circuit bleeder valve.
15. Install a transparent hose over the end of the bleeder valve, then repeat steps 7 11.
16. With the right front wheel hydraulic circuit bleeder valve tightened securely - after all air has been purged from the right front hydraulic circuit - install a proper box-end wrench onto the LEFT FRONT wheel hydraulic circuit bleeder valve.
17. Install a transparent hose over the end of the bleeder valve, then repeat steps 7-11.
18. After completing the final wheel hydraulic circuit bleeding procedure, ensure that each of the 4 wheel hydraulic circuit bleeder valves are properly tightened.
19. Fill the brake master cylinder reservoir to the maximum-fill level with Delco Supreme 11, GM P/N 12377967 (Canadian P/N 992667), or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container.
20. Slowly depress and release the brake pedal. Observe the feel of the brake pedal.
21. If the brake pedal feels spongy, repeat the bleeding procedure again. If the brake pedal still feels spongy after repeating the bleeding procedure, perform the following steps:
21.1. Inspect the brake system for external leaks. Refer to Brake System External Leak Inspection.
21.2. Pressure bleed the hydraulic brake system in order to purge any air that may still be trapped in the system.
22. Turn the ignition key ON, with the engine OFF. Check to see if the brake system warning lamp remains illuminated.

Important: If the brake system warning lamp remains illuminated, DO NOT allow the vehicle to be driven until it is diagnosed and repaired.

23. If the brake system warning lamp remains illuminated, refer to Symptoms - Hydraulic Brakes.

 

[imiceman44]

I am so happy I don't live in the rust belt.
I don't think I will have that problem on my 98.
All my other trucks are no ABS.
Good luck with this.

 

[Blue85]

AFAIK, the bleeding issue is not rust-related. Just the difficulty in getting stuff apart. Of course, if the truck lived in the desert, these lines wouldn't have failed. I understand that the '00-'03 or so lines rusted much faster, but I have no idea about the GMT400's. 330,000 miles driven year-round in MI before it failed, that's actually a good quality part.

Yeah, most of the official instructions say to do base bleeding before bothering with the scan tool, which is why that hasn't been officially holding me up, I more wondered if something was stuck in there that would free up by cycling the system. I should mention that I've tried turning the key on and off multiple times and disconnecting the battery, as I've heard it does something to initialize the unit. I've also tried bleeding with the key on.

Something else that crossed my mind: there is a junction block/valve thing underneath the master cylinder with a rubber cap on the end. It may have no purpose other than triggering the "Brake" light in the cluster (which is illuminated, BTW). Maybe I should get something to hold it. This could be a safety that reduces how much fluid it pukes when there's no pressure in the back.

 

[imiceman44]

AFAIK, the bleeding issue is not rust-related. Just the difficulty in getting stuff apart. Of course, if the truck lived in the desert, these lines wouldn't have failed. I understand that the '00-'03 or so lines rusted much faster, but I have no idea about the GMT400's. 330,000 miles driven year-round in MI before it failed, that's actually a good quality part.

Yeah, most of the official instructions say to do base bleeding before bothering with the scan tool, which is why that hasn't been officially holding me up, I more wondered if something was stuck in there that would free up by cycling the system. I should mention that I've tried turning the key on and off multiple times and disconnecting the battery, as I've heard it does something to initialize the unit. I've also tried bleeding with the key on.

Something else that crossed my mind: there is a junction block/valve thing underneath the master cylinder with a rubber cap on the end. It may have no purpose other than triggering the "Brake" light in the cluster (which is illuminated, BTW). Maybe I should get something to hold it. This could be a safety that reduces how much fluid it pukes when there's no pressure in the back.

It's not rust related but if no rust, no replacement, hence no need for full line bleeding which i think is the problem

 

[Wes Harden]

If you fell up to it, drive it. Get the abs module activate, then try your base bleed again.
Piston in module maybe stuck

 

[Truckman4life]

I bet this is your issue. Especially since you said you had a sudden loss of rear pressure and the rears won't bleed properly. The shuttle valve in the proportioning valve(the thing under the master) is supposed to shift when there is a line that blows and it will shut off fluid to either the front or rear circuit and trigger the brake warning light. My '83 had it happen. There is a little plastic tool you install in place of the brake warning switch to hold it centered til you get the system bled. They also sell metal ones.

 

[Truckman4life]

Tool looks like this. You just gotta get the correct one that fits your vehicle.

 

[Blue85]

If you fell up to it, drive it. Get the abs module activate, then try your base bleed again.
Piston in module maybe stuck

I don't dare drive until I have some pedal. Plus, there is pretty much no chance of the ABS activating with no brake power, although that instruction above makes it sound like something happens at 8MPH. Too bad I haven't fixed the parking brake.

I bet this is your issue. Especially since you said you had a sudden loss of rear pressure and the rears won't bleed properly. The shuttle valve in the proportioning valve(the thing under the master) is supposed to shift when there is a line that blows and it will shut off fluid to either the front or rear circuit and trigger the brake warning light. My '83 had it happen. There is a little plastic tool you install in place of the brake warning switch to hold it centered til you get the system bled. They also sell metal ones.

Supposedly there is some kind of cross-circuit on cars, where you lose 1 front and 1 rear, but the other 2 still work. That valve has 2 lines from the master coming in the top and 4 lines going out, so that must be its function. If that theory is correct, I should be able to bleed the FL, but not the FR. This all makes good sense, but I've never seen a proportioning valve lock one up like this - including when this truck broke the front line. It obviously is not a complete stop because the pedal was sinking with every press.

Will try and report back.

Something else that crossed my mind: there is a junction block/valve thing underneath the master cylinder with a rubber cap on the end. It may have no purpose other than triggering the "Brake" light in the cluster (which is illuminated, BTW). Maybe I should get something to hold it. This could be a safety that reduces how much fluid it pukes when there's no pressure in the back.

 

[cheavyk10]

Damn, I swapped fresh calipers on the rear of my '04 Tahoe and had no idea this could be an issue. I guess I didn't lose enough fluid for it to be a problem.

 

[Blue85]

I think that's exactly the difference. I've swapped calipers on my Yukons multiple times without issue. Just lightly clamp the rubber line and it's no problem. In fact, this pair is recent enough I was able to get the bleeders to turn out with *just* a week of PB Blaster and a few minutes with a torch. They love to snap off.

For work like this, I like to remove the bleeder, wrap it in Teflon tape and reinstall, so air doesn't suck through the threads. Anybody just leave Teflon in there permanently? Anti-seize doesn't really work because you can't help but dissolve it in brake fluid.

 

[Wes Harden]

It's onlyva problem if you step onbthe prake pedal when the lines are open. Shuttle doesn't shift even if all the fluid is drained.
Yes the proportion valve would stop 1/2 of the brake system from bleeding. That could be a front rear divide or dual diagonal. Front right left rear, and front left right rear.
The only device on this truck that can seperate ea wheel is the abs module. The modue can easily trap moisture in the actuator piston chambers, and rust.

Might time to invest in bi directional scanner. It would be very easy to operate the abs module. Dies your current scanner show any abs codes

 

[Blue85]

Sure enough, the valve was shuttled backwards. It centered easily with a small screwdriver, but no change in how it won't bleed.

It's only a problem if you step on the brake pedal when the lines are open.

Does your current scanner show any abs codes

Of course I stepped on it with the line open. The line blew out in the middle while I was trying to get down the hill from dropping the garbage. Had to let off the brake a few times going downhill to get more fluid in before the pedal was in the carpet. Manually shifted the auto where practical. As for trouble codes, my Innova 1000 will have to stop being a commie state software tethered device to know.

 

[Blue85]

Bought a tool today and shot at least 1/2-quart from the caliper forward and over-filled the reservoir. Still no action from the pedal or trying to vacuum bleed the caliper.

 

[Blue85]

FL bled fine. FR is up next. That will ensure there's fluid everywhere. Then I'll take the RL line off at the ABS to be 100% sure where the blockage is. I'm curious if 12V can be applied to the motor somehow to move it.

 

[Wes Harden]

Why yes it can. The bi direction scan tool turns the solenoids on, so all you have to do is proably provide a ground with the key onbto make them function

 

[Blue85]

The interesting thing is that the hydraulic unit and the electronics are in 2 separate packages, with the interaction being magnetic. The posts on the pump fit inside the control solenoids when they're mated together. Theoretically you could bring your own electromagnet or even permanent magnet maybe to actuate them. I don't know if the pump would need to be powered. I assume the pump provides pressure to shuttle the valves. You would think the default has to be open/no restriction, but maybe one is stuck. I have no idea if it's smart enough to enter that state on purpose based on not having pressure rise in that line.

I just don't see how it can be completely blocked when the line was still shooting fluid while pulling into the garage and then it continued to drip overnight.

 

[Blue85]

FR brake bled completey fine. Pedal feels normal. It stops OK in FWD and REV in the shop. Looking forward to testing ABS once I can figure out where the keys are for the car that parked behind the garage.

 

[Blue85]

It drives fine. Pedal feels OK. Does log some traction control errors (which isn't really new), but ABS actuates as expected. The problematic LR brake is not raising much above ambient, while the other 3 are hot. Brake light is off.

 

[Blue85]

It occurs to me that with a non-clamping brake, the ABS will never need to actuate at that corner. AFAIK, the traction control can apply the brakes (and I activated it several times), but I don't know if that's the same action as cutting brake pressure. This doesn't seem like a control module failure, more like a mechanical issue inside the "pump" section. Even junkyard pulls aren't cheap and that swap means inevitable DOT-3 shower, then hours of bleeding, but that may be where this is headed.