C8 brake bleed discussion
Instructor
Joined: Nov 2019
Posts: 197
Likes: 114
From: Edmond, OK
I haven't done it on a C8, but that is the procedure I have used on every vehicle I've had. If you do it exactly as you describe, and tighten the bleed screws without letting pressure drop, there is zero chance of introducing air in the system, and there is no way to mess it up. I would not go all the way down to min line (I'm just paranoid about it), just in case the electric booster kicks in or you inadvertently leave the bleed screw open too long.
I've been doing this forever. Every time I changed brake pads I repeat the above procedure to get old fluid out of the calipers. This way I always have fresh fluid in the system.
Your procedure is still the best way, IMHO. Good luck.
P.S. I assume you have a clear tube and bottle to catch the bled fluid. Good way to detect air, impurities, etc. You can also buy a fluid moisture tester and keep track of moisture content on your fluid. (hint: you will never see any significant moisture on a newer, well maintained car)
I've been doing this forever. Every time I changed brake pads I repeat the above procedure to get old fluid out of the calipers. This way I always have fresh fluid in the system.
Your procedure is still the best way, IMHO. Good luck.
P.S. I assume you have a clear tube and bottle to catch the bled fluid. Good way to detect air, impurities, etc. You can also buy a fluid moisture tester and keep track of moisture content on your fluid. (hint: you will never see any significant moisture on a newer, well maintained car)
Supporting Vendor
Joined: Jul 2007
Posts: 30,982
Likes: 406
From: Raleigh NC
I have done 2 cars now with the pedal method. No issue.
On the second one with the front calipers off I had to open the door /reconnect battery etc and of course the car complained.
Got it all bled and yes it took a few minutes to cycle and clear codes but it worked fine.
I use gravity (14.7 psi) and then the master cyl. to create pressure. I tried a Motive once on a different car but it felt over complicated and exposed the fluid to so much air. I like having the nearest person with a leg describe the firm pedal.
YMMV
-Ken
On the second one with the front calipers off I had to open the door /reconnect battery etc and of course the car complained.
Got it all bled and yes it took a few minutes to cycle and clear codes but it worked fine.
I use gravity (14.7 psi) and then the master cyl. to create pressure. I tried a Motive once on a different car but it felt over complicated and exposed the fluid to so much air. I like having the nearest person with a leg describe the firm pedal.
YMMV
-Ken
Racer
Joined: Jun 2013
Posts: 489
Likes: 272
I'm confused here. Why do you guys need to reconnect the battery to open the door to press the pedal (for those using that method)?
Can't you just use the mechanical release on the floor or the mechanical key on the fob?
Can't you just use the mechanical release on the floor or the mechanical key on the fob?
Melting Slicks
Joined: Jun 2012
Posts: 2,226
Likes: 1,029
From: Thomas Texas
There is always that one guy who figures it out and tells you a better way after you’ve already made that mistake.
Racer
Joined: Jun 2013
Posts: 489
Likes: 272
Been there, done that (mistakes while working on my cars) countless times. I appreciate that you have gone through it, so we can learn from you.
Track Rat
Joined: Oct 2006
Posts: 6,466
Likes: 3,464
Originally Posted by CZS
Has anyone used their Motive bleeder to pressure bleed their C8 brakes yet? I'm about to order the Motive kit, but am a total novice to using it. My plan is to remove some fluid from the master cylinder, then top off with fresh fluid and use the Motive to pressure bleed each caliper until the fluid level is down to just above the 'minimum' line. Then fill and repeat until all four corners are bled. Anyone used this method successfully yet?
I did buy another cap and quick disconnect for the motive that seal better, it's the same one I use on the C7. Also note that you need to add fluid very slowly to the reservoir to fill it in between bleed cycles.
2nd Gear
Joined: Aug 2019
Posts: 2
Likes: 0
Good question - Any body have an answer from actual C8 DIY?
On the weekend schedule, love to know what the experience is with just using pressure bleeder to keep reservoir filled on C8. THANKS!
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Melting Slicks
Joined: Feb 2000
Posts: 3,425
Likes: 567
From: new orleans
Changed the fluid to SRF probably about a month after getting the car in August of 2020. I pressure bleed all the calipers after 2 track days to put fresh fluid I the calipers. Been SRF since then, and check the water content of the fluid with a Brake fluid checker and it has always been fine. I see no reason to change back to a lower grade of fluid after a track day. IMO
Pro
Joined: Sep 2018
Posts: 664
Likes: 302
From: Nova Scotia Canada
I see many people use the Motive bleeder to PUSH fluid through. Although I do have a Motive bleeder I prefer my other bleeding tool which draws fluid through. Has anyone else tried this method? I find it less messy too.
Race Director
Joined: Aug 2016
Posts: 12,766
Likes: 10,201
From: Garden Valley CA
If you are talking about a vacuum bleeder GM recommends not to use one.
Racer
Joined: Apr 2024
Posts: 353
Likes: 180
From: Michigan
There are really nice pressure bleeders, and while many have Motive, I find Ares makes a far superior unit with much better fitting caps and quick disconnects.
Pro
Joined: Feb 2021
Posts: 690
Likes: 177
The best way to bleed is with a fluid pusher. The professional units use a diaphragm to separate the air from the new fluid. The second would be the two-person method.
The motive bleeder is a non-separate bleeder that is designed to push the new fluid with air. It appears some use it to just pressurize the system. This is not ideal because it does not separate the air from the fluid. The effects of the humidity, and aspiration of the fluid becomes more of a factor. When using the motive bleeder, the way it was designed, which is to push the fluid will reduce the negative effects of the air pressure since it is working against a larger volume of fluid. The issue is that this method can be messy, although no worse than the gold standard diaphragm bleeders.
Vacuum bleeding should not be used since the sealing in the brake system is designed to be loaded from the inside.
I have used the Motul RBF dot 4 fluids (600) for many track cars with good results and have used it on the street without any issues. They also offer it in a 660, 700 and 5.1. I have very little experience with the 5.1, (not the same as dot 5) and has a higher boiling point then the dot 4.
.
The motive bleeder is a non-separate bleeder that is designed to push the new fluid with air. It appears some use it to just pressurize the system. This is not ideal because it does not separate the air from the fluid. The effects of the humidity, and aspiration of the fluid becomes more of a factor. When using the motive bleeder, the way it was designed, which is to push the fluid will reduce the negative effects of the air pressure since it is working against a larger volume of fluid. The issue is that this method can be messy, although no worse than the gold standard diaphragm bleeders.
Vacuum bleeding should not be used since the sealing in the brake system is designed to be loaded from the inside.
I have used the Motul RBF dot 4 fluids (600) for many track cars with good results and have used it on the street without any issues. They also offer it in a 660, 700 and 5.1. I have very little experience with the 5.1, (not the same as dot 5) and has a higher boiling point then the dot 4.
.
Last edited by Drew888; Nov 18, 2024 at 05:46 PM.
Racer
Joined: Aug 2018
Posts: 255
Likes: 94
From: West Palm Beach, Florida
There are really nice pressure bleeders, and while many have Motive, I find Ares makes a far superior unit with much better fitting caps and quick disconnects.
https://www.amazon.com/gp/product/B07CP79C7S/
https://www.amazon.com/gp/product/B07CP79C7S/
Racer
Joined: Apr 2024
Posts: 353
Likes: 180
From: Michigan
I used the 49.5mm adapter which was an additional purchase above and beyond the bleeder. I couldn't find a Ares part number with this size adapter online at the time, but for me it works for all 4 of my vehicles (3 gm and 1 Ford).