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Brake Bleed Procedure

hoitzed
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hoitzed Enthusiast

hoitzed

Posted
Posted

Hi,

 

I have a 2019 AT4 which is at the 5  year mark for brake fluid.  I haven't seen any posts on bleeding the brakes, just on pad replacements.  I wanted to confirm that no particular service mode is required for just bleeding, and it follows the same basic procedures as older models: add fluid, and pump out starting from RR, RL, FR, FL?

 

Thanks

newdude Senior Enthusiast

newdude

Posted
Posted (edited)
1 hour ago, hoitzed said:

Hi,

 

I have a 2019 AT4 which is at the 5  year mark for brake fluid.  I haven't seen any posts on bleeding the brakes, just on pad replacements.  I wanted to confirm that no particular service mode is required for just bleeding, and it follows the same basic procedures as older models: add fluid, and pump out starting from RR, RL, FR, FL?

 

Thanks

 

 

A scan tool is required.  You have to deactivate the booster and also perform an automated bleed and hydraulic leak test.

Edited by newdude
MaverickZ71 Senior Enthusiast

MaverickZ71

Posted
Posted
2 hours ago, newdude said:

 

 

A scan tool is required.  You have to deactivate the booster and also perform an automated bleed and hydraulic leak test.

 

Same procedure or the old-school method on a 2009 1500 4x4?

newdude Senior Enthusiast

newdude

Posted
Posted
1 hour ago, MaverickZ71 said:

 

Same procedure or the old-school method on a 2009 1500 4x4?

 

 

Old school on an 09 unless you think you need to bleed the ABS pump, there's a scan tool bleed for that.  

 

T1 trucks the booster is also the ABS module and pump and its all electronic and boost-by-wire.  The brake pedal is still attached to the "booster" but there is sensors and stuff to interpret the boost given.  

  • Thanks 2
hoitzed Enthusiast

hoitzed

Posted
  • Author
Posted

Does that mean without the scantool on the T1's to turn off the booster, it just won't bleed, bleed incompletely, or result in other issues (CEL / malfunctions)?

newdude Senior Enthusiast

newdude

Posted
Posted
On 10/30/2024 at 1:17 PM, hoitzed said:

Does that mean without the scantool on the T1's to turn off the booster, it just won't bleed, bleed incompletely, or result in other issues (CEL / malfunctions)?

 

 

To change the fluid for the entire brake system, it must be disabled.  The lines are still manually bled as normal after that, but that can not be done unless the system is disabled.  

 

Steps are:

 

- Fill the reservoir to max

 

- Unplug the level sensor

 

- Disable the booster with a scan tool

 

- Do a "base bleed" aka a traditional bleed.  GM calls for doing it with a pressure bleeder tool.  

 

- Perform an automated brake bleed with a scan tool 

 

- Disable the booster with scan tool again and repeat the base bleed to get any remaining air out

 

- Perform hydraulic system test with scan tool.  If that fails after 3 attempts, inspect for leaks. 

 

repairman54 Enthusiast

repairman54

Posted
Posted

I just gravity bleed, keeping the MC full at all times to avoid ABS pump issues. 

Mostly clean fluid is better than none in the system in my personal vehicles. Drove multiple year Express vans on my job taken to over 250k miles for years than never had a brake fluid change as fleets don't do that. They just replace calipers and bleed enough to get the caliper working again when needed. 

  • Like 1
hoitzed Enthusiast

hoitzed

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Posted

So I did a gravity bleed.. and our reservoirs are tiny! I may have let it get too low, and now I have no brakes at all.  The DIC is throwing all sorts of ESC, Brake, Trailer Brake, and ABS errors, and there is no stopping power.  Anything I should attempt before towing it to the dealer?

newdude Senior Enthusiast

newdude

Posted
Posted
1 hour ago, hoitzed said:

So I did a gravity bleed.. and our reservoirs are tiny! I may have let it get too low, and now I have no brakes at all.  The DIC is throwing all sorts of ESC, Brake, Trailer Brake, and ABS errors, and there is no stopping power.  Anything I should attempt before towing it to the dealer?

 

 

I'm gonna say it...but should have just taken it there to begin with.  Scan tool is needed to bleed it.  

hoitzed Enthusiast

hoitzed

Posted
  • Author
Posted

well deserved "i told you so".  $200 every 5 years, not worth the hassle of doing it yourself.  I just thought I'd give it a go since I had extra fluid from doing my canyon. Guess things changed quite a bit from 2017 to 2019..

newdude Senior Enthusiast

newdude

Posted
Posted (edited)
6 hours ago, hoitzed said:

well deserved "i told you so".  $200 every 5 years, not worth the hassle of doing it yourself.  I just thought I'd give it a go since I had extra fluid from doing my canyon. Guess things changed quite a bit from 2017 to 2019..

 

 

Was it a 15-22 Canyon?  Those take DOT 3, Silverado 19+up takes DOT 4.  3 and 4 are compatible, sure, however, GM does spec DOT 4 in there for its higher boiling points and I wouldn't go to the lower boiling spec DOT 3.  

Edited by newdude
  • 1 year later...
carkhz316 Enthusiast

carkhz316

Posted
Posted (edited)

I end up using GDS2 for certain GM vehicle functions, including Brake System Plunger Motor Position Sensor Learn and the Hydraulic Circuit Installation Verification when doing some of the brake repairs on Tx trucks and SUVs. Some scan tools won't run the routine(s) properly.

 

I like to flush the brake fluid on my vehicles periodically, but unless you absolutely need to perform an automated bleed to rid the EBCM of fluid, then I would recommend a manual or pressurized flush/ exchange and call it a day. Do this with the battery disconnected and you won't have to run the aforementioned routines.

Edited by carkhz316
  • 3 months later...
needafix New Member

needafix

Posted
Posted

I'm not sure if this should be a reply on this thread or a new topic, let me know if it's out of place. This my first post. Thanks

85077522 - ACDelco GM Genuine Parts Brake Master Cylinders. Anyone else had to replace this brake master cylinder yet. I didn't do any brake work, it looks like new parts and I've had the truck for about 4k miles. When it started to throw codes I did the calibrations with a bidirectional scanner and got the codes to clear but they came back so i did the routine; base bleed, automated bleed and final base bleed. All that with Bosch ES16-32N fluid (please look it up). That seemed to fix it but 100ish miles later it failed again so I ran the same process but with a pressure bleeder this time and got the same results, fixed for 100ish miles. The original fluid looked bad and I thought I got most of it out. The codes; P25A2, C05B0-00, C2A1B. I can get them to clear but not for long. The C05B0 indicates a leak in the front circuit (which is bone dry) so I'm thinking of doing the bleed process on that front again today and I don't know if that's taboo to just do the front but at this point it seems like it's worth the try anyway. The new master cylinder/module unit is supposed to get here today. But now I'm pretty much convinced this install is over my head. I've called several shops and some mobile guys that I know but this thing is like radio active material scary wise. I did get 2 local shops say they should be able to do it, one says he has the SPS2 programing capability. And with the battery disconnected is there supposed to be pedal resistance, mine is to the floor, then if I pump it I can get some resistance.

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