DIY Clutch Delay Valve (CDV) Removal

Stvee

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First up, this article covers why you would want to remove your clutch delay valve: https://www.zeckhausen.com/catalog/index.php?cPath=6562

In short, the CDV makes clutch engagement inconsistent and annoying for anyone who is used to driving manual cars. This is especially noticeable on the 1-2 shift with these cars. Removing it just makes the clutch engagement feel like every other car.

In certain use cases it may also help to extend clutch life. For those already experiencing clutch slip, this is not going to be a magic fix.

Tools/materials required:
Small screwdriver
8mm socket
9mm socket
11mm wrench
~2 inch wood screw (make sure the end of the screw isn't slotted like with decking screws, it makes it hard to grip the CDV)
3 feet of 3/16" ID vinyl tubing
1 bottle of BMW DOT 4 brake fluid for bleeding or whatever you normally use

~1 hour of time if you've never done this before


1. After the car is in the air, remove the under tray pictured below by removing 10 8mm bolts

IMG_6922.JPG



2. After removing this tray, you should see the transmission as pictured below. The CDV will be located to the left. You will want to use a 9mm socket to remove 2 plastic nuts holding the metal shield partially pictured at the very left to gain better access to the CDV.

IMG_6923.JPG


3. Once this is removed, you will have enough access to remove the hard clutch fluid line from the slave cylinder where the CDV is located. You do not need to remove the 12mm bolt holding the clutch line bracket. There is more than enough room to move that line around without removing the bracket. It might not hurt to slightly loosen it if needed.

Before separating the clutch line from the slave cylinder, use a hose clamp on the soft rubber line at the bottom left below. This will prevent more brake fluid from draining than is necessary. Even with a hose clamp in place, you will still lose some clutch fluid. Have something underneath to catch it.

The CDV location is pointed out in the picture below. Simply use a small screwdriver to pry the clip up enough to separate the hard line from the slave cylinder. The clip does not need to be completely removed. You can see how much I pulled it up in a picture further down.

IMG_6925.JPG


4. Once the clutch line is separated from the slave cylinder, insert a 2" wood screw into the very center of the slave cylinder opening where the CDV is located and twist until you feel it grip the CDV. Make sure you have a good screw with sharp edges at the tip or you may have issues with this part.

At this point you should just be able to pull the CDV and rubber spacer out with a minimal amount of force. There isn't anything holding it in like other styles of CDV BMW has used in the past.

IMG_6929.JPG


The culprit removed

IMG_6931.JPG




5. Now all that is left to do is reattach the hard clutch line to the slave cylinder and bleed the clutch. Attach a 3 foot long piece of 3/16" ID vinyl tubing to the bleed valve for clutch bleeding. This is located on the slave cylinder as well.

IMG_6930.JPG



I'm not going to cover the specifics of clutch bleeding because it's the same as on any other BMW and there are tons of guides already out there that cover this. I personally used a Motive power bleeder but the old clutch pumping method should be fine as well.


*** I should also mention that instead of removing the CDV itself from the slave cylinder, you can replace the whole slave cylinder with the version from the E90 chassis below. It's the same thing but does not contain the CDV like our cars. It was located in a different position on those.

BMW part# 21526785964 -- costs around $80
Sponsored

 
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Stvee

Stvee

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Before anyone asks, yes it is worth it. This is the 4th BMW manual I've had and it's the 4th time I've removed the CDV. Every time I remove it, I only wish that I had earlier.

After removing the CDV it actually takes your brain a little to re-calibrate to shifting into second normally. You end up compensating in the opposite direction since you don't have to pause a split second to shift smoothly as you would with the CDV in place.
 

RaceReX

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First up, this article covers why you would want to remove your clutch delay valve: https://www.zeckhausen.com/catalog/index.php?cPath=6562

In short, the CDV makes clutch engagement inconsistent and annoying for anyone who is used to driving manual cars. This is especially noticeable on the 1-2 shift with these cars. Removing it just makes the clutch engagement feel like every other car.

In certain use cases it may also help to extend clutch life. For those already experiencing clutch slip, this is not going to be a magic fix.

Tools/materials required:
Small screwdriver
8mm socket
9mm socket
11mm wrench
~2 inch wood screw (make sure the end of the screw isn't slotted like with decking screws, it makes it hard to grip the CDV)
3 feet of 3/16" ID vinyl tubing
1 bottle of BMW DOT 4 brake fluid for bleeding or whatever you normally use

~1 hour of time if you've never done this before


1. After the car is in the air, remove the under tray pictured below by removing 10 8mm bolts

IMG_6922.JPG



2. After removing this try, you should see the transmission as pictured below. The CDV will be located to the left. You will want to use a 9mm socket to remove 2 plastic nuts holding the metal shield partially pictured at the very left to gain better access to the CDV.

IMG_6923.JPG


3. Once this is removed, you will have enough access to remove the hard clutch fluid line from the slave cylinder where the CDV is located. You do not need to remove the 12mm bolt holding the clutch line bracket. There is more than enough room to move that line around without removing the bracket. It might not hurt to slightly loosen it if needed.

Before separating the clutch line from the slave cylinder, use a hose clamp on the soft rubber line at the bottom left below. This will prevent more brake fluid from draining than is necessary. Even with a hose clamp in place, you will still lose some clutch fluid. Have something underneath to catch it.

The CDV location is pointed out in the picture below. Simply use a small screwdriver to pry the clip up enough to separate the hard line from the slave cylinder. The clip does not need to be completely removed. You can see how much I pulled it up in a picture further down.

IMG_6925.JPG


4. Once the clutch line is separated from the slave cylinder, insert a 2" wood screw into the very center of the slave cylinder opening where the CDV is located and twist until you feel it grip the CDV. Make sure you have a good screw with sharp edges at the tip or you may have issues with this part.

At this point you should just be able to pull the CDV and rubber spacer out with a minimal amount of force. There isn't anything holding it in like other styles of CDV BMW has used in the past.

IMG_6929.JPG


The culprit removed

IMG_6931.JPG




5. Now all that is left to do is reattach the hard clutch line to the slave cylinder and bleed the clutch. Attach a 3 foot long piece of 3/16" ID vinyl tubing to the bleed valve for clutch bleeding. This is located on the slave cylinder as well.

IMG_6930.JPG



I'm not going to cover the specifics of clutch bleeding because it's the same as on any other BMW and there are tons of guides already out there that cover this. I personally used a Motive power bleeder but the old clutch pumping method should be fine as well.


*** I should also mention that instead of removing the CDV itself from the slave cylinder, you can replace the whole slave cylinder with the version from the E90 chassis below. It's the same thing but does not contain the CDV like our cars. It was located in a different position on those.

BMW part# 21526785964 -- costs around $80
thanks Steve.

although I don’t own a manual one at the moment, I will eventually, so this is good info. Really appreciate it.

now, for the record, why does BMW do this?

is this designed for those who are bad manual shifters? I’ve met more than a few.
 

Joker328

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thanks Steve.

although I don’t own a manual one at the moment, I will eventually, so this is good info. Really appreciate it.

now, for the record, why does BMW do this?

is this designed for those who are bad manual shifters? I’ve met more than a few.
Pretty much. It's to reduce drivetrain lashing from people who dump the clutch too abruptly. If you are not smooth with your clutch release, you will put all of that torque back into the drivetrain, which will increase wear over time. The CDV slows the clutch engagement (whether you want it to or not), so the clutch takes the abuse rather than the expensive metal parts. The problem is it makes the clutch feel like it has a mind of its own and makes it even harder to shift both quickly and smoothly.
 

Supra_UK_

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Hi,

Non-mechanic / non-dyi guy here - so I read a lot about this cdv topic, and how some are saying it can lead to pre-mature clutch wear - is this true, can someone explain?

And, how does the Supra's rev matching affect cdv / cdv issues?
If the wear on the clutch is caused by two speeds mismatched, but the rev match aligns those 2 speeds resolving this discrepancy, does the cdv still mess up that adherence?

Or are we saying this is only a problem (cdv/clutch slip) when upshifting then?

Thanks :)
 

nashcarr

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I had that same question. Does the delay valve exist for the rev matching feature?
 

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Hi,

Non-mechanic / non-dyi guy here - so I read a lot about this cdv topic, and how some are saying it can lead to pre-mature clutch wear - is this true, can someone explain?

And, how does the Supra's rev matching affect cdv / cdv issues?
If the wear on the clutch is caused by two speeds mismatched, but the rev match aligns those 2 speeds resolving this discrepancy, does the cdv still mess up that adherence?

Or are we saying this is only a problem (cdv/clutch slip) when upshifting then?

Thanks :)
It's only a problem in the mind as far as I'm concerned. Go out and start your car and put it in first gear raise the rpm to say 1200 bring the clutch up to just before the friction point then side step the clutch pedal. If it doesn't stall and you pull away without any issues then I'll believe the anti clutch valve people. If it stalls then it's all a load of shit.

Phil
 

Supra_UK_

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It's only a problem in the mind as far as I'm concerned. Go out and start your car and put it in first gear raise the rpm to say 1200 bring the clutch up to just before the friction point then side step the clutch pedal. If it doesn't stall and you pull away without any issues then I'll believe the anti clutch valve people. If it stalls then it's all a load of shit.

Phil
Thanks Phil
 

Allenyao09

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That explains why the 1-2 shift is always so jerky. I thought it was the big mass flywheel causing the rev hang. Thanks for the write up. I will add this to my list.
 
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Stvee

Stvee

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I had that same question. Does the delay valve exist for the rev matching feature?
No they've been using CDV's since the mid 90's. It doesn't affect the auto rev matching at all.
 

Spart

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That explains why the 1-2 shift is always so jerky. I thought it was the big mass flywheel causing the rev hang. Thanks for the write up. I will add this to my list.
It has an effect any time you need to quickly find the bite point. 1-2 shift, heel-toe and rev matching, hill starts, aggressive launches.

Coming from a car without the CDV, it was immediately noticeable that something was goofy with the clutch engagement, but I didn't know what. It was just inconsistent. I had never heard of this whole CDV thing with BMWs, my only knowledge of them was from something in the same vein - the accumulator in the Tacoma.

I'm very happy with the manual driving experience in the car now. It does what I want and I don't have to think about it.
 

Spart

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I had that same question. Does the delay valve exist for the rev matching feature?
I would wager that it's almost the other way around. It's difficult enough to heel-toe and rev match manually in this car, that in stock form having the rev-match turned on is probably going to feel like a requirement to most people.

BMW looked at a problem they created, and decided to gloss over it with driver aids instead of providing a better driving experience.
 
 




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