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Tricky To Bleed C8 Brakes

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  • #31
    It is NOT brake by wire. It is electric power assist, nothing more. That's been confirmed by GM.

    Especially given that GM's own instructions say you have to disconnect power to service the brakes, the statement that you can't do that seems pretty dumb.
    SunKissed, my 2015 2LT, 7MT, Black over Daytona Sunrise Orange Metallic, Stingray convertible (One of about 40)

    Purchased 5/2/2015,
    >36,000 miles

    Proud member of the Old Dominion Corvette Club. Check us out http://www.olddominioncorvetteclub.org

    Never grow up - It's a trap.

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    • #32
      GM would use their own tools to command ABS wheel positions on/off when bleeding or replacing brake fluids
      Due to the costs of GM tools, most vehicle owners would not have them

      If owning a good OBD-II scanner tool and it has bi-directional control
      allows sending a command to each wheels ABS control which allows then to open/close ABS unit to allow fluid to flow
      through each wheel position

      Here is an example, and you can see commands for each wheel position (inlet and outlet)

      Click image for larger version

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      Corvettes owned, wrenched on and raced since 1975:
      1974,75,77,84,87,89,91,93,94 ZR-1 & 1999 Mallett 435

      Comment


      • #33
        Originally posted by Neil H View Post
        It is not "Brake by Wire".
        It is electronic/electric boost as compared to hydraulic or vacuum boost.
        Here's another thread:

        https://www.midenginecorvetteforum.c...-wire-function
        Yeah I shouldn’t have used that term. But it’s still separated and according to the owners manual you will loose boosted assist in a power loss.

        Comment


        • #34
          Originally posted by Panic Button View Post

          Do we know for a fact that a scan tool is needed? There's no mention of a scan tool in the GM Techlink article I read.

          But of coarse, the article doesn't really do into much detail, so how does one know for sure since I don't think there are any repair manuals out there for the C8 yet.

          If there are some sources available, I'd really be interest in looking at them.
          I'd say it is highly unlikely that a scan tool would be required to bleed the brakes. Per the owners manual you need to put in high boiling point fluid before tracking a Z51 and remove it before using it on the street. Track rats would be up in arms if they had to purchase a scan tool to track their car.
          On Deposit: 2020 C8 Stingray Convertible - Torch Red - Natural Dipped 3LT - Z51 w/MSRC - Front Lift

          Comment


          • #35
            Originally posted by RKCRLR View Post

            I'd say it is highly unlikely that a scan tool would be required to bleed the brakes. Per the owners manual you need to put in high boiling point fluid before tracking a Z51 and remove it before using it on the street. Track rats would be up in arms if they had to purchase a scan tool to track their car.
            Scan tools do not have bi-directional control to command the ABS solenoids for no reason

            Yes you can replace fluid without it, but by doing it allows a complete replacement of fluid with opening solenoids through that fluid path

            If you flush the fluid out, then you will need a Tech II (or OBD-II scanner) to cycle the ABS solenoid valves and pump to get any dirty fluid or air out of them as you are bleeding the lines.

            As for the pump and solenoid valves during a power flush without cycling the ABS with a tech II, it not air,
            but only small amounts of old fluid that will cycle out the first time the ABS activates instead.

            Note,
            Power flushing is driving the old fluid out of the lines (including those for ABS and its unit) with new fluid until the fluid is running clear, and at no time do you allow air to get in the lines.
            Corvettes owned, wrenched on and raced since 1975:
            1974,75,77,84,87,89,91,93,94 ZR-1 & 1999 Mallett 435

            Comment


            • #36
              Originally posted by RoketRdr View Post

              Yeah I shouldn’t have used that term. But it’s still separated and according to the owners manual you will loose boosted assist in a power loss.
              I am almost certain that there always will be a mechanical link between your foot on the brake pedal and the master cylinder piston to create at least some hydraulic pressure to apply the brakes.
              I believe it is one of the biggest safety requirements on any vehicle with hydraulic brakes.

              I also would assume that the electric boost system would have a hydraulic accumulator, like ABS systems have, to give you one, maybe 2 brake applications at close to normal boost pressure, the same way a vacuum assisted system would work.
              The trick there, in an emergency situation is to apply and hold the brake because as soon as you release the brake pedal, you have less reserve of the high pressure fluid to use.
              Once you deplete the high pressure reserve and get down to manual pressure only, you really have to stand on the brakes and you might bend the steering wheel because you are pushing so hard -- at that time you have no boost -- and you are probably filling you pants!

              All of this, of course, is my opinion & needs to be corroborated with GM's info.
              TPW March 2. 3LT, Z51, FE4, Black GBA, ZZ3, Black interior with Red seats/red stitch HU0 & 2 tone TU7, E60, J6N, RIK, Q8Q, etc.
              Medicine Hat, Alberta, Canada

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              • #37
                Originally posted by Teamzr1 View Post

                Scan tools do not have bi-directional control to command the ABS solenoids for no reason

                Yes you can replace fluid without it, but by doing it allows a complete replacement of fluid with opening solenoids through that fluid path

                If you flush the fluid out, then you will need a Tech II (or OBD-II scanner) to cycle the ABS solenoid valves and pump to get any dirty fluid or air out of them as you are bleeding the lines.

                As for the pump and solenoid valves during a power flush without cycling the ABS with a tech II, it not air,
                but only small amounts of old fluid that will cycle out the first time the ABS activates instead.

                Note,
                Power flushing is driving the old fluid out of the lines (including those for ABS and its unit) with new fluid until the fluid is running clear, and at no time do you allow air to get in the lines.
                Yea, I meant to say a Tech II. As long as you don't do something that gets air in the system most people will be able to do a fluid flush as long as they are careful.
                On Deposit: 2020 C8 Stingray Convertible - Torch Red - Natural Dipped 3LT - Z51 w/MSRC - Front Lift

                Comment


                • #38
                  I'll second that emotion. There is nothing like the Motive Power Products pressure bleeder. You never have to worry about introducing air into the system if you do it correctly. I've found that using the Harbor Freight setup, for me anyway, can sometimes turn into a bit of a mess. I recently purchased speed bleeders, and after installing them and then again using the Motive Products bleeder, I can't think of a better setup.

                  I track my C7 Z51 all summer and have been for the last five seasons not including 2020. (Except for lately.........), and I usually end up bleeding the system three times a season. And that's with high quality/high temp racing brake fluid.
                  2015 Z51 Stingray
                  2018 Honda Goldwing
                  2018 Suzuki V-Strom

                  Comment


                  • #39
                    As long as there is brake fluid in the Motive PB tank and pressure keep up in it really full proof way of replacing fluid and not getting air into the system

                    I also use a bleeder one way valve on a hose off the caliper bleeder which allows flow only one direction (outward) so no air can be pulled in from that direction
                    As fluid is flowing out the bleeder and shutting it then no air can be pulled into brake system

                    You can go directly to Motive website at (they are in Canada)
                    https://www.motiveproducts.com/

                    I suggest you get the metal brake tank cover over the plastic one that comes with the PB as
                    I had issues of it leaking fluid under pressure and Motive sells a metal one

                    or

                    Can buy Motive PB for $55 at Amazon

                    https://www.amazon.com/Motive-Produc.../dp/B00CJ5DWKO

                    Handy in other uses like putting fluid in tranny or rear end

                    Metal cap is must better design then the plastic one is

                    Click image for larger version

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                    Last edited by Teamzr1; 04-04-2020, 12:36 AM.
                    Corvettes owned, wrenched on and raced since 1975:
                    1974,75,77,84,87,89,91,93,94 ZR-1 & 1999 Mallett 435

                    Comment


                    • #40
                      I've got the metal cap also. But only thing I wish is that there was a pressure relief valve on the bottle so I wouldn't have to unscrew the cap to relieve the pressure. But no doubt, it's a killer tool. I ditched the Harbor Freight one. Another thing it's really great for, but with adaptors, is reverse bleeding motorcycle brakes forcing fluid directly into the calipers.
                      2015 Z51 Stingray
                      2018 Honda Goldwing
                      2018 Suzuki V-Strom

                      Comment


                      • #41
                        Originally posted by VetteStromWing View Post
                        I've got the metal cap also. But only thing I wish is that there was a pressure relief valve on the bottle so I wouldn't have to unscrew the cap to relieve the pressure. But no doubt, it's a killer tool. I ditched the Harbor Freight one. Another thing it's really great for, but with adaptors, is reverse bleeding motorcycle brakes forcing fluid directly into the calipers.
                        Good point
                        On mine I installed a wheel tire stem so I can add or bleed air-pressure without using the hand pump
                        Corvettes owned, wrenched on and raced since 1975:
                        1974,75,77,84,87,89,91,93,94 ZR-1 & 1999 Mallett 435

                        Comment


                        • #42
                          Originally posted by Teamzr1 View Post

                          Good point
                          On mine I installed a wheel tire stem so I can add or bleed air-pressure without using the hand pump
                          Pictures/description to include parts used?!
                          2015 Z51 Stingray
                          2018 Honda Goldwing
                          2018 Suzuki V-Strom

                          Comment


                          • #43
                            Originally posted by VetteStromWing View Post

                            Pictures/description to include parts used?!
                            Just take a tire valve stem and mount it in location that the stem can be installed from the inside and then
                            bit of sealant glue on outside around stem

                            Now can easy connect to a air-compressor hose and keep a constant rate of pressure within fluid in tank

                            Click image for larger version

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                            Click image for larger version

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                            Corvettes owned, wrenched on and raced since 1975:
                            1974,75,77,84,87,89,91,93,94 ZR-1 & 1999 Mallett 435

                            Comment


                            • #44
                              Originally posted by Teamzr1 View Post

                              Just take a tire valve stem and mount it in location that the stem can be installed from the inside and then
                              bit of sealant glue on outside around stem

                              Now can easy connect to a air-compressor hose and keep a constant rate of pressure within fluid in tank

                              Click image for larger version

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                              Click image for larger version

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                              Awesome, thanx!!!
                              2015 Z51 Stingray
                              2018 Honda Goldwing
                              2018 Suzuki V-Strom

                              Comment


                              • #45
                                Does the Motive Products brake bleed adapter cap fit the C8 reservoir (enough to hold the pressure)?
                                Shadow Gray Metallic; 1LT with Z51, FE4, Comp seats, blk int and package with PDR.

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