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Thread: Clutch Delay Valve compilation (CDV delete)

  1. #1
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    Clutch Delay Valve compilation (CDV delete)

    This is a compilation of information regarding the Clutch Delay Valve and its removal from manual transmission BMW Z3s. This is a common modification which allows the driver to have more control over the clutch engagement speed. Many experienced manual transmission drivers found the CDV to hinder the timing and smoothness of clutch engagement, and benefit from its removal. See the links below for more information regarding the purpose and result.


    What is a Clutch Delay Valve and what does it do?

    The following website explains the CDV for 01-02 non-M Z3s. The description of the effect of the CDV in the article reflects both the bolt type CDV (01-02 non-M Z3s) and the restrictive clutch line “CDV” (All model years of the M Z3s)

    http://www.zeckhausen.com/CDV.htm
    Note: Zeckhausen offers a modified CDV to replace the original CDV for 01-02 non-M Z3s. The included walk-through does not involve the modified CDV. The modified CDV will maintain a factory appearance, but will not make the removal process any easier.


    Does my Z3 have a CDV or restrictive clutch line “CDV”?
    *Only manual transmission Z3s have a CDV or restrictive clutch line "CDV".

    Some model year Z3s and M-Z3s have enough evidence to say with confidence, that they have the CDV or restrictive line “CDV”. Other model years of non-M Z3s have conflicting evidence regarding the presence of a CDV or restrictive line “CDV”s. I’ve included a chart to help clarify which model years have been confirmed by more than one source, to have the bolt type CDV or to have the restrictive line “CDV”.


    B = Bolt type CDV - - - - - L = Restrictive line “CDV” - - - - - ? = No strong enough evidence to report


    I’m hoping more people with 96’-00’ non-M Z3s come forward with information regarding the presence of a CDV or restrictive line within this thread. I will update the chart accordingly if so.

    Realoem.com is a great source for parts researching. Rtav on bimmerforums.com has researched realoem’s database and found it suggests that all 96’-00’non-M Z3s have the Restrictive line “CDV”. I have found no evidence searching many CDV, rough shifting, and stuck shifter threads to support realoem’s part number search results. I have a few 96’-00’ non-M Z3 owners who claim to have checked and found no CDV or restrictive line “CDV”. We need 96’-00’ non-M Z3 owners to verify whether or not there car was built with either the type of CDV device. Please post your findings within this thread, or PM me at JaBr1884 on bimmerforums.com.

    Informative CDV related threads on bimmerforums.com:
    For those who broke their search function…

    Trouble removing a flange nut:
    http://forums.bimmerforums.com/forum/showthread.php?t=852553&highlight=cdv+delete

    Which cars have what debate:
    http://forums.bimmerforums.com/forum/showthread.php?t=1251485&highlight=CDV

    Supportive information:
    http://forums.bimmerforums.com/forum/showthread.php?t=1113168&highlight=CDV

    Aftermarket or stock replacement line for Ms:
    http://forums.bimmerforums.com/forum/showthread.php?t=1103373&highlight=CDV

    After bleeding the slave:
    http://forums.bimmerforums.com/forum/showthread.php?t=1246699&highlight=bleeding+the+sl ave


    What else do I need to know if I want to remove it?

    If you decide to remove your CDV or restrictive clutch line “CDV”, you must bleed the slave cylinder. The tutorial within this thread will walk you through bleeding the slave cylinder using a pressure bleeder on a non-M, and may cover Ms well enough. There are several ways to bleed the slave cylinder; the old fashioned way of pumping the clutch requires two people. The pressure bleeder included in the walk through below makes this entire project capable of being performed by one person. After either of the bleeding methods is performed, it is advisable to remove the slave cylinder and depress the plunger. I do not have a walkthrough with pictures, but I’ll list the steps below. You should also visit the “After bleeding the slave:” informative thread link above.

    Written steps:

    Thanks to clintjg on bimmerforums.com
    To completely bleed the slave cylinder you have to do the following after using the pedal-pump or pressure bleeding methods:
    1) Unbolt the slave cylinder from the gearbox
    2) Attach a tube from the bleeder screw to a small bottle
    3) Hold the slave cylinder so that the bleeder screw is pointing straight up*
    4) Open the bleeder screw
    5) Push the rod/piston all the way in to the slave cylinder
    6) While holding the rod/piston in, close the bleeder
    7) Repeat steps #4-#6 two or three times
    8) Ditch the tube and old fluid.
    9) Bolt the slave cylinder back in place, be very careful that the tip of the rod lines up with the indentation on the fork


    What do I need to remove it, and how do I do it?
    *Do not loosen the clutch line without fully understanding how to bleed the slave cylinder


    Restrictive clutch line “CDV” (All model year M Z3s):

    Follow the guide in the following link:

    Thanks to E368 S52 and 2kredz3 on bimmerforums.com
    http://forums.bimmerforums.com/forum/showthread.php?p=16265428


    Clutch Delay Valve (CDV; 01’-02’ non-M Z3s):

    This is a Clutch Delay Valve (CDV) removal and slave bleeding procedure for a 2001-2002 2.5L or 3.0L Z3. This walk-through is intended for those who need more direction and are less familiar with such DIY projects. I used a pressure bleeder, which is not required unless you wish to follow the walk-through exactly.

    Please read the entire walk-through before attempting this procedure.

    Things you will need: Thanks to E368 S52 on bimmerforums.com

    Optional: PB Blaster: Spray the nuts the night before if corroded.
    17mm Flare Nut Wrench
    11mm Flare Nut Wrench
    14mm Regular Wrench (for CDV bolt)
    7mm Regular Wrench (for bleed bolt)
    1 Clamp or Vise Grip
    ~2ft of Clear Tubing
    Optional: Pressure Bleeder (needed to follow the guide for bleeding)
    Optional: Turkey baster (needed to follow guide for bleeding)
    Brake Fluid (DOT 4, ATE Super Blue recommended, 1L can is more than enough)
    Drip pan to catch Brake Fluid
    Jack and jack stand(s)


    Preparing the car: (I used a 2 ton jack with two jack stands)

    1: Place the car on solid, level ground. Use the e-brake and put the car in gear. Turn the car off.
    2: On the driver’s side, place the jack in the middle of the beam, between the jack supports.
    *In the picture, the jack stand is next to the jack support under the front, driver’s side of the car.

    3: Raise the car until a jack stand is able to slide under the front driver’s side jack support.
    4: Lower the car onto the jack stand and slide a second loosely under the beam for added support.
    *The second jack stand could be used on another jack support if desired.

    5: Remove the jack.


    Removing the CDV:

    1: Slide under the car, near the transmission, and locate the CDV and its surroundings.
    (Have your wrenches, clamp, and pan close enough to reach while under there.)
    *I found it easiest to slide under the driver’s side door.

    2: Clamp the clutch line as shown in the picture below.

    3: Place the drip pan under the CDV.
    4: Place the 14mm regular wrench on the CDV.
    5: Place the 17mm flare wrench on the clutch line bolt.
    *Forgive my crude Photoshop job.

    6: Make sure of the proper rotation, and break loose the CDV-clutch line bolt connection.
    7: Remove the 17mm clutch line bolt wrench.
    8: Place the 11mm flare wrench on the slave line bolt.
    *Forgive my crude Photoshop job.

    9: Make sure of the proper rotation, and break loose the CDV-slave line bolt connection.
    10: Loosen the slave line from the CDV by rotating in the loosening direction, removing one of the wrenches, rotate in the tighten direction, replace the second wrench, loosen rotation, repeat.
    11: Remove the wrenches and separate the slave line and CDV.

    12: Separate the CDV from the clutch line by hand, or wrench if needed.

    13: Attach the slave line directly to the clutch line, through the existing support bracket.

    14: Tighten the slave line to the clutch line by using the 11mm flare wrench and the 17mm flare wrench appropriately. Tighten the bolts by rotating in the tightening direction, removing one of the wrenches, rotating in the loosening direction, replacing the second wrench, tightening rotation, repeat.
    15: Remove the wrenches, clamp, and drip pan.


    Bleeding the slave:

    1: Locate the brake fluid reservoir in the engine bay.
    *Located toward the rear of the engine bay, on the driver’s side.

    2: Remove the cap and the filter.
    *A flat head screwdriver may help with removing the filter.

    3: Use the turkey baster and drip pan to empty the brake fluid reservoir.


    4: Replace the filter and fill the reservoir with new brake fluid.
    5: Apply the Pressure bleeder to the reservoir.
    *I chose not to put brake fluid in the pressure bleeder.
    6: Set the pressure on the bleeder to ~18 psi.
    7: Slide back under the car, near the transmission, and locate the slave.
    (Have your 7mm wrench, clear tube, and drip pan in reach while under there.)

    8: Remove the cap from the bleed valve.
    9: Fit the clear tubing to the end of the bleed valve.

    10: Use the 7mm wrench to open the bleed valve until a steady flow is sustained.
    *If super blue was used, you will see the change from yellow to blue brake fluid.
    *Continue to drain until no bubbles are seen in the line, and the old fluid is gone.

    11: Tighten the valve and remove the hose.
    12: Replace the cap for the bleed valve.
    13: Remove any tools or parts from under the car.
    14: Release the pressure from the bleeder by removing the bleeders cap.
    *As suggested by the Motive brand bleeder I used.
    15: Remove the bleeder fitment from the reservoir.
    16: Add brake fluid to the reservoir once more to the full mark.
    17: Place the cap back onto the brake fluid reservoir.
    18: Test the bleeding by pressing in the clutch pedal.
    (If bled properly, the clutch pedal should feel as it did prior to the CDV removal.)
    (If there is less resistance in the clutch pedal, there is air in the line. Bleed again.)
    19: Dispose of any extra brake fluid. It is not useable once opened.

    Test drive your car, and report back with your experience and additional advice!
    Last edited by JaBr1884; 01-04-2010 at 06:18 PM.

  2. #2
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    great write up :-) ill try and get you the data i said i would

  3. #3
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    Thanks, that'd be great 2k. I'm also hoping for some constructive criticism.

  4. #4
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    well, its interesting in the written directions you mention pulling the slave cylinder from the bell housing to finish the drain. while i have not done that on any of the cars i have done a flush on today i ran into a snag on a 4 cyl car. bentley outlined taking the slave off but i couldnt see any reason why. the snag was after doing the flush the clutch didnt disengage. it took about 2 min of pumping after the system was all closed and no bubbles were coming through the hose anymore before i got pressure back. the car had 175k mi on so im thinking it is a problem with a worn slave but i suppose they put that step in there for a reason? can you confirm you did that when you bled yours?

  5. #5
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    Correct me if I'm wrong, but cliffnotes are like this:

    remove CDV, tighten slave line back to clutch master cyl, bleed lines
    "If the Corvette is a rebellious child of the extended automotive family, the M coupe is the blackest of sheep." - via Car & Driver

  6. #6
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    Quote Originally Posted by 2kredz3 View Post
    the car had 175k mi on so im thinking it is a problem with a worn slave but i suppose they put that step in there for a reason? can you confirm you did that when you bled yours?
    I also did not remove the slave and have not had a problem with air that I know of. Others have had air in their line until they removed the slave and depressed the plunger. I wanted to include that information for those who may have trouble with air in their lines after bleeding. The hydrolic line feels the same for me after the cdv delete, so I believe if there is air in the lines due to not removing the slave, it's so minute it won't make a difference. The only reason I didn't remove the slave and depress the plunger is because the sun was going down and rain was expected. I still plan to remove the slave and depress the plunger to see if there is any difference.

    Adonnan,
    Those cliffnotes, if you are refering to the 01'-02' non-M Z3s sound correct except you are working with the lines only, and not the actual clutch master cylinder. Really, it should be:

    remove CDV, connect Slave line directly to clutch line, bleed lines.

  7. #7
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    98 2.8 no CDV

  8. #8
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    Thanks jmai, no restrictive line as well? The one removed in the walkthrough for the M Z3s.

  9. #9
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    good work - thanks
    2000 Z3 MCoupe, '01 LSB E46 M3, '99 GTI VR6, '06 Audi A4, Andrew '95 Avus M3

  10. #10
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    Very good consolidation of information.

    Like 2kredz3 said, when we did my car we didn't remove the slave to do a final bleed. It still engages fine and is not much different than pre-cdv delete as far as pedal resistance, But I do occasionnally have difficulty putting it in 1st gear and it was like this even before the cdv delete. Anyone know if it's because I didn't remove the slave to bleed it? Just some extra info, I was never able to properly utilize my clutch stop because if it's dialed in to just be able to shift the gears, I could never get it into 1st gear from a stand still. Now that I have it to where I can get it into 1st gear, it's not much of a clutch stop because the travel is more than I need for shifting through the other gears. Anyone have thoughts on this?


  11. #11
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    98 2.8 also seems to have a non-restrictive hose. I think it is recommended to use a Z3 hose as a replacement for the restrictive Z3M hose.

  12. #12
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    Quote Originally Posted by jmai View Post
    98 2.8 also seems to have a non-restrictive hose. I think it is recommended to use a Z3 hose as a replacement for the restrictive Z3M hose.
    That is correct jmai, the non-M hose is recommended to replace the restrictive hose found on all M Z3s. UUC also offers a stainless steel alternative which is less affected by higher temporatures. That said, one end of the UUC line is smaller than the stock line so for the best result, modification to the UUC line is recommended. It us much easier for the M Z3 owners to order the stock non-M Z3 clutch line.

    Thanks for the confirmation on the non-restrictive line on your 98 2.8L.

  13. #13
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    A few years old, but I'm just chiming in for the chart,
    My 99 prefacelift with the M52TUB25 and a build date of 11/98 doesn't have a CDV.

  14. #14
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    Has anyone asked why the valve was placed in the line to begin with? Any correlation between CDV removal and rear pan splits or increased guilbo failures? Just a thought.
    Dan "PbFut" Rose

  15. #15
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    Quote Originally Posted by PbFut View Post
    Has anyone asked why the valve was placed in the line to begin with? Any correlation between CDV removal and rear pan splits or increased guilbo failures? Just a thought.
    I have read that it is there to take some of the "user error" out of engaging/disengaging the clutch while shifting making for smoother transistions between gears.

    I deleted mine and have noticed that I can shift quicker.

  16. #16
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    What does it do regarding pedal pressure? Lighter or the same? If no change, does that have more to do with the compression & return springs?

  17. #17
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    Quote Originally Posted by spacecowboy
    What does it do regarding pedal pressure? Lighter or the same? If no change, does that have more to do with the compression & return springs?
    Pedal pressure is all in the pressure plate, and how well your slave cylinder works. I would say the biggest difference I was able to notice was in how smooth I was able to shift.

  18. #18
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    Euro 1998 Feb build 2.8i - No CDV

    The CDV is there to restrict the speed at which the pedal can come back up, so it acts like a buffer to save wear on the clutch.

    Problem is it can make it feel heavier and harder work.

    Combine this with faulty design with clutches from BMW from 2006-2011 and it makes the judder 100x worse. BMW had a big issue that would never be a recall as it effected every manual they made between this period in regular non M cars, millions.
    My wife had the x1 with a manual 'box back in 2010 and it was atrocious, the CDV deleted it made it driveable but was still horrid, and in 2011 I managed to get BMW to put the revised clutch and flywheel into the car, it was a dream after that.

    The funny thing was it is the only time BMW have ever worked on a car and refused to give me any paperwork for the work done, that was the agreement. I would get a new clutch and flywheel, but there would be no paperwork for me to take or logged on the system.

    The CDV is there to reduce warranty claims from people who don't really know how to drive a manual, nothing more than that.

  19. #19
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    hmmm. guess i better climb under mine and see. it's a 2KM so, seems it came with it...
    shifts like butter though...
    2KredZ3 worked his magic on it last spring... highly recommended.

  20. #20
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    Quote Originally Posted by crashgordan View Post
    hmmm. guess i better climb under mine and see. it's a 2KM so, seems it came with it...
    shifts like butter though...
    2KredZ3 worked his magic on it last spring... highly recommended.
    If it shifts like butter leave it alone.

  21. #21
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    Quote Originally Posted by crashgordan View Post
    hmmm. guess i better climb under mine and see. it's a 2KM so, seems it came with it...
    shifts like butter though...
    2KredZ3 worked his magic on it last spring... highly recommended.
    Don't worry yours is already gone...done with the clutch line i installed ;-)

  22. #22
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    A thought just occurred to me... of those that have had CDV problems, how many have flushed the clutch fluid? Those that had problems after flushing, how many used the correct fluid? Super Blue, as recommended in the first post, is NOT the correct fluid. DSC systems used DOT4-LV.


    /.randy

  23. #23
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    Iv only used super blue once and it was fine. The rest has been DOT 4 Amsoil, which is compliant with low viscosity.

  24. #24
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    Quote Originally Posted by 2kredz3 View Post
    Don't worry yours is already gone...done with the clutch line i installed ;-)

    that's why YOU ROCK!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

    Kelly Williams ROCKS!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

    2kredZ3 ROCKS!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

    Mod Squad Motorsports ROCKS!!!!!!!!!!!!!!!!!!!!!

    ok. now back on topic

  25. #25
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    Thank you for the kind words!

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