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if you mean removing them from the bracket leaving the brake lines disconnected, no you don't have to clear codes. It's a general rule of thumb to disconnect the battery with modern cars and brake systems.
If you're removing the brake lines, you probably also don't have to clear codes as long as you bleed the system.
yea id be completely removing them off the car for paint/powder
With the C8 it's more than a rule of thumb, it's a decision to keep your thumbs.
There shouldn't be any codes if the battery is disconnected. For some odd reason the GM tech manual says to also disconnect the brake fluid level sensor (why if the battery is also disconnected????)
Also, to bleed the brakes it requires a pressure bleeder per the GM procedure. Supposedly you can't vacuum bleed this system. Getting a cap to seal and hold pressure was a chore for me, but I found a good cap that seals well and holds pressure.
The problem with this cap is it has a proprietary top brass QD fitting. I popped an o-ring into the groove, attached hose and used an oetiker clamp fitting to hold it all together. This cap has an internal expanding o-ring seal that expands when you turn the black ****.
On my C8 the 1118 sprayed oil everywhere. I believe the issue is the chevy dealer that I had service my vehicle damaged the top edge of the reservoir neck and created some nicks in the plastic that prevent the motive (and several other caps) from sealing properly and they leak like crazy.
The tesla cap above works well. It is just tricky to get it installed. You have to turn the black **** until the o-ring starts to expand a little before trying to install the cap. When you turn the ****, it causes a center hub that has a beveled edge to expand the o-ring, but it also reduces the height of the hub under the cap. This has to happen for you to get the cap far enough down to engage the lugs on the filler neck. Once the cap goes on and turns to lock in place you can then further tighten the black **** to expand the internal o-ring to seal with the ID of the filler neck. I slowly applied pressure and if it started to leak, just tightened the black **** further. Once it was holding pressure, just left it alone and it held pressure.
Last edited by dohabandit; Nov 23, 2023 at 08:54 PM.
Does the battery disconnect require re-training the window open/close?
Should one open the windows or leave the door open before disconnecting the battery?
Does the battery disconnect require re-training the window open/close?
Should one open the windows or leave the door open before disconnecting the battery?
Sometimes it doesn't require reindexing when the battery is disconnected but it isn't a big deal when it does.
I recommend leaving the driver's window down and the door closed when doing pads since you are going to want to pump the brakes without reconnecting the battery. With the window down you can reach in and pull the manual release to open the door. If you disconnect the battery with the window up and the door open the window will hit the top if you close the door.
Isn't the C8Z brake by wire? I didn't think pumping the brakes with the battery disconnected would do anything.
Thanks, trying to pre-game this before doing it this weekend.
The assist is controlled by wire but it is still a full hydraulic system connected to the pedal. You will still have brakes with a complete power failure (albeit without assist).
If you are bleeding the brakes or you push the pistons back to replace the pads you need to pump the brake pedal several times to get the new pads seated against the rotors. If you do this while the battery is connected you can confuse the computer and make it think there is something wrong which could require a code to be cleared.
I know most have said not to vacuum as per GM, but I would like to hear there explanation? I owned a brake shop for 30 years and had all of the different bleeder systems and the vacuum ones always seemed to work the best. Just make sure you dont let the resevoir run dry. This is still a sealed system like all the newer GM vehicles, I will give a few things a try and report back with results. One thing for sure is the vacuum systems are alot less messy.
Somewhere I read there’s a secondary reservoir you can’t see. It’s possible a vacuum may somehow run that dry without pulling from the primary reservoir you can see.
Why try something that’s specifically recommended NOT to do? Seems like you’d have to be a glutton for punishment.
Somewhere I read there’s a secondary reservoir you can’t see. It’s possible a vacuum may somehow run that dry without pulling from the primary reservoir you can see.
Why try something that’s specifically recommended NOT to do? Seems like you’d have to be a glutton for punishment.
You must know me, lol. I am a gluten for punishment. I owned a brake repair shop for 25 years and am very interested in the inner workings of this system. Have seen a lot of speculation of the reasons not to do it, but no concrete answers. I wont do it without knowing whats going on in the system, but always hated the mess made while pressure bleeding.
Old fashioned way. Just push the new fluid out of the system with the pedal topping off as you go. You can do this by yourself as long as you keep the tube from the caliper in a container with fluid in it. Just don't run the reservoir dry. And doing it this way without a pressure bleeder doesn't make you open and close the bleeder a lot which guards against any thread issues (low risk but this system won't tolerate any pressure issues in the system even if extremely minor).
Old fashioned way. Just push the new fluid out of the system with the pedal topping off as you go. You can do this by yourself as long as you keep the tube from the caliper in a container with fluid in it. Just don't run the reservoir dry. And doing it this way without a pressure bleeder doesn't make you open and close the bleeder a lot which guards against any thread issues (low risk but this system won't tolerate any pressure issues in the system even if extremely minor).
If I have to bleed it, for now thats what I would do. I really dont want to cause an unneeded problem, but after doing this kind of stuff for years would like to find out how this system works. I will keep on looking and if i find out i will post when i do. Steve
Just to help out, this cap worked great. Inner o-ring seal fits perfectly and no marring of the reservoir attachment points. I use it with an OMT pressure bleeder. It’s much nicer than my motiv pressure bleeder and has quick connect fittings.
ARES 18054-49.5mm Master Cylinder Adapter - for Use with Late Model GM and Some Mazda Master Cylinders - Use 70921, 18051, and 18053 Brake Fluid Bleeders Only
Last edited by spearfish25; Apr 1, 2024 at 08:29 AM.
Isn't the C8Z brake by wire? I didn't think pumping the brakes with the battery disconnected would do anything.
Thanks, trying to pre-game this before doing it this weekend.
Originally Posted by RKCRLR
The assist is controlled by wire but it is still a full hydraulic system connected to the pedal. You will still have brakes with a complete power failure (albeit without assist).
If you are bleeding the brakes or you push the pistons back to replace the pads you need to pump the brake pedal several times to get the new pads seated against the rotors. If you do this while the battery is connected you can confuse the computer and make it think there is something wrong which could require a code to be cleared.
The master cylinder is a brake by wire when it is operating properly with battery connected. When the pedal applies brake pressure, the direct hydraulic circuit is disconnected/blocked. Then the brake pedal makes force on a "pedal simulator" which measures the brake pedal force with pressure sensors and converts that to an electric signal that controls an actuator and piston pushing fluid through the normal hydraulic circuit. Whenever power is off, lost, or there is a controller failure, the pedal simulator chamber remains directly connected to the hydraulic circuit and fluid can be manually pushed through the circuit. Again, during normal operation a solenoid closes off the direct hydraulic circuit creating a closed volume with pressure sensors that measure the pedal force and convert that to an electric signal.
