BluePrint Engines

Visit our community sponsor

Thanks Thanks:  0
Likes Likes:  0
Results 1 to 10 of 10

Thread: Pressure Bleeding / CNC1459A

  1. #1
    Senior Member RickP's Avatar
    Join Date
    Feb 2016
    Location
    Boyertown, PA
    Posts
    683
    Post Thanks / Like

    Pressure Bleeding / CNC1459A

    I have recently upgraded my FFR supplied single brake reservoir with the dual CNC reservoirs. This required replacing all the hosing from reservoirs to Master Cylinders (Wilwood). In my attempt to bleed the brakes in the traditional manner, I am no longer able to push fluid out any of the calipers while my significant other is working the pedal. Leads me to believe I have introduced a big pocket of air into the MC's.

    I came across a thread where EdwardB recommends pressure bleeding using part CNC1458A. This makes sense to me except a couple of questions have come up in my head. Part CNC1458A appears to have a Schrader valve installed on the cap, which begs the question, is the air pressure applied to the cap constant, or is the cap pressurized then source air removed? Should I backup and bench bleed the reservoirs before trying to pressurize the system(s)?

    1. how much air pressure?
    2. are the reservoir bellows left in place?
    3. will I be expected to pressurize the cap, crack a caliper valve, then re-pressurize the cap, until I get all air past the MC and out the caliper end?


    RickP

  2. #2
    Senior Member cv2065's Avatar
    Join Date
    Dec 2017
    Location
    Orlando, FL
    Posts
    1,837
    Post Thanks / Like
    If you look at post #124 in my build thread, you can see my comments around the process.

    Regarding pressure amount, its very little, which is why I went to a handheld pump. I'd say 2lbs at best. If you get this pump, you can use one hand and feel it tightening up and you'll know you're at the limit. I pressurized, cracked the valve, let it drain for a couple of minutes, then closed and pressurized again. Had to do multiple rounds before it all came out.

    You don't have to bench bleed the masters, but I did bleed them in the car. Not sure if its necessary with this method though.

    https://thefactoryfiveforum.com/show...d-Thread/page4
    Last edited by cv2065; 02-17-2019 at 09:33 AM.
    MKIV Roadster - #9380 - Complete Kit - Delivered 7/17/18 - SOLD 5/2023
    Build Thread #1: https://thefactoryfiveforum.com/show...V-Build-Thread
    MKIV Roadster - #TBD - Complete Kit - Delivered 11/6/23 - In Progress
    Build Thread #2: https://thefactoryfiveforum.com/show...Build-Thread-2

  3. #3
    Senior Member
    Join Date
    Mar 2011
    Location
    Heart of Dixie, Alabama
    Posts
    1,849
    Post Thanks / Like
    Make sure your master cylinder piston can return to full release. The push rod coming off the pedal needs a little free play. Hope this is what it takes. You should be able to gravity bleed, if this was the issue.
    20th Anniversary Mk IV, A50XS Coyote, TKO 600, Trunk Drop Box, Trunk Battery Box, Cubby Hole, Seat Heaters, Radiator hanger and shroud.

  4. #4
    #9160 BB767's Avatar
    Join Date
    May 2017
    Location
    Chehalis, WA
    Posts
    400
    Post Thanks / Like
    Hi Rick,

    Ditto what cv said.

    Yes on #3 above. Pressurize the system, bleed the air, close the bleeder, re-pressurize and repeat. (Unless you have two people and can maintain a constant pressure.)

    No on #2. The fluid needs to have constant pressure, the bellows would fill and either stop the flow or burst.

    I spent a week trying to properly bleed my brakes the old fashioned way of pump and bleed, never did work right on these. My theory is that air is sucked in around the MC valve seal, it is not designed for negative pressure and air entered easier and quicker than the fluid could when releasing the pedal. Some MC's may have better seals than others.

    Be sure as you pressurize and bleed that the reservoirs do not run low on fluid! If they do you will simply be pumping air back into the system. The goal is to keep a constant but small amount of pressure on the fluid while you are opening the valves to let air out. But obviously you will have to occasionally open the cap to check the fluid level so it will take a number of cycles to get all the air out.

    This method should work easily for you once you get the hang of it.
    MK4 - complete kit - Blueprint 427W - Holly Sniper EFI - TKO 600 .64 - 3.55 3 link - 17" Halibrands

  5. #5
    Papa's Avatar
    Join Date
    Dec 2016
    Location
    Parker, CO
    Posts
    5,594
    Post Thanks / Like
    I used the CNC bleeder cap to do mine as well and like others have said, it works very well. I did bench bleed the master cylinders first and would recommend it. As the name would seem to imply, you don't need to remove the master cylinders to "bench" bleed them. Just make a short piece of tubing that goes from the MC back into the top of the reservoir. Fill the reservoir and pump the brake pedal until it is bubble-free. Re-attach your brake lines and proceed to pressure bleeding. It only takes 2-4 lbs. of pressure on the cap and I used a hand-held pump. Start at the right-rear caliper (or the furthest from the reservoir). Attach a piece of tubing to the bleeder valve to catch the fluid that will come out of the caliper. Open the valve and let the fluid flow until there are no air bubbles. This may take a few times, ensuring that the reservoir never runs dry!!! Next move to the next furthest caliper and repeat. Once I hit all four, I went back through them just to be sure I didn't have any additional trapped air in the system.
    My Build Thread: http://thefactoryfiveforum.com/showt...ter-Build-9754
    (Most viewed Roadster build thread on this forum!)

    Delivered: 6/17/2017
    First Start: 12/30/2017
    Completed: 12/7/2019
    Legal: 1/30/2020

    Member of the Mile-Hi Cobra Club
    Dave's Cobra YouTube Channel: https://www.youtube.com/channel/UCbk...npK1UZHj4R-bYQ
    Agora 1:8 Scale Cobra Build: https://thefactoryfiveforum.com/show...l-Build-Thread

  6. #6
    Senior Member jrcuz's Avatar
    Join Date
    Sep 2013
    Location
    Stafford Virginia
    Posts
    675
    Post Thanks / Like
    When I pressure bled mine I called CNC and was told no more than 5#
    JR
    Mk4 complete kit #9059 ordered 1/19/17 delivered 3/23/17, 2015 IRS, Fortes/DART347,TKO 600, hyd clutch, P/S, 12.88 wilwood brakes front and rear, heater/defrost and vintage gauges
    First start and go-cart 4/11/18. Taken To Whitby Motorcars Greensboro, N.C. 2/5/21 for body/paint

  7. #7
    Senior Member edwardb's Avatar
    Join Date
    Feb 2011
    Location
    Lake Orion, Michigan
    Posts
    10,547
    Post Thanks / Like
    I've used the CNC pressure approach on all my builds and it hasn't let me down yet. On my Coupe build, didn't have room for CNC reservoirs (at least where I wanted to mount them) so used a similar unit, although plastic, from Tilton. They don't offer a pressure cap. So bought a spare regular Tilton cap and added my own Schrader valve. Worked fine. I also bench bleed first, exactly as Papa described. Not sure it's necessary, but at the least gets a bunch of air out right from the start. I use my air compressor and turn the regulator way down until I have 4-5 pounds at the end of the air hose. The process is simple, as others have described. Pressurize the reservoir (without the bellows if there is one), go to the caliper, crack the bleeder with a hose in container. I use a small Ball jar with a hole in the lid. The first time, you will probably need to pressurize multiple times. I typically go all around at least twice just to be sure all the air is out. Agree to watch the level in the reservoirs. But you would need to run it a lot to drain it. One word of caution no one has mentioned -- do not under any circumstances push the brake pedal down while the system is under pressure. In other words don't mix this process with the pumping pedal approach for bleeding. Pretty good chance you could damage seal(s) in the MC's. Another hint is this seems to work fine with the Wilwood dual MC setup. Some have had issues with using the standard brake pedal pump method along with the Wilwood balance bar setup. To the point where it's been recommended to do front and back at the same time if pumping the pedal. Nothing like that needed with the pressure setup. Once you're done, fill the reservoirs to the recommended level(s), and replace with the regular cap. Should be good to go.
    Last edited by edwardb; 02-17-2019 at 01:45 PM.
    Build 1: Mk3 Roadster #5125. Sold 11/08/2014. Build 2: Mk4 Roadster #7750. Sold 04/10/2017. Build Thread
    Build 3: Mk4 Roadster 20th Anniversary #8674. Sold 09/07/2020. Build Thread and Video. Build 4: Gen 3 Type 65 Coupe #59. Gen 3 Coyote. Legal 03/04/2020. Build Thread and Video
    Build 5: 35 Hot Rod Truck #138. LS3 and 4L65E auto. Rcvd 01/05/2021. Legal 04/20/2023. Build Thread. Sold 11/9/2023.

  8. #8
    Senior Member RickP's Avatar
    Join Date
    Feb 2016
    Location
    Boyertown, PA
    Posts
    683
    Post Thanks / Like
    Thank you gents for all the input.

    Sounds like I'm on the right track. I did "bench bleed" the cylinders while in the car originally, and subsequently gravity bled the calipers. Took about 4 attempts over a couple of weeks to get it right. Now that I have mucked with the system, I'm back at it. In the end, I will feel much better about having the fronts/rears on their own separate systems.

  9. #9
    Member ChasNMe's Avatar
    Join Date
    Sep 2018
    Location
    Charleston, SC
    Posts
    80
    Post Thanks / Like
    anyone try speed bleeders? seems like that would be pretty simple, especially by yourself

  10. #10
    Senior Member edwardb's Avatar
    Join Date
    Feb 2011
    Location
    Lake Orion, Michigan
    Posts
    10,547
    Post Thanks / Like
    Quote Originally Posted by ChasNMe View Post
    anyone try speed bleeders? seems like that would be pretty simple, especially by yourself
    I've used speed bleeders before, and they work OK if you're doing the traditional pedal pushing method for bleeding. The pressure bleed method described here is also easy by yourself and the speed bleeders wouldn't really help or change the process. The other thing is some have had issues with the pedal push style bleed with the Wilwood dual MC/balance bar setup. Pressure bleeding isn't affected by that.
    Build 1: Mk3 Roadster #5125. Sold 11/08/2014. Build 2: Mk4 Roadster #7750. Sold 04/10/2017. Build Thread
    Build 3: Mk4 Roadster 20th Anniversary #8674. Sold 09/07/2020. Build Thread and Video. Build 4: Gen 3 Type 65 Coupe #59. Gen 3 Coyote. Legal 03/04/2020. Build Thread and Video
    Build 5: 35 Hot Rod Truck #138. LS3 and 4L65E auto. Rcvd 01/05/2021. Legal 04/20/2023. Build Thread. Sold 11/9/2023.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

Breeze

Visit our community sponsor