[TurboAra]

Hello, I have a 2013 335 with a 6 speed. I have read through countless threads trying to figure out where the CDV is on this car or if it even has one. After beginning to get some excessive slip going from 1st to 2nd under full throttle I decided to remove the slave cylinder and found what looks to be a metal restriction on the inlet for the Slave. I attempted to drill the plate and In the process was able to have the plate pull out on the drill bit. There is 2 rubber seals, 1 cone shaped that should get put on the hard line end but will most likely get stuck in the slave, and one that’s perfect round and is holding in the metal plate, these can easily be removed with a pick. After reassembly, it took me longer trying to bleed the hydraulic system now that there is lots of air in the master and slave. I tried the gravity bleed method and pump bleed and even using a brake power bleeder kit. I spent hours and nothing worked. I watched a YouTube video showing reverse bleed procedure pushing new fluid through the slave, I gave that a try this morning. I used a clean hospital syringe and it worked flawless, I was done in 30 mins. I haven’t tried the 1st 2nd shift full throttle again but I can say the clutch pedal operates smoother and slightly easier to push, also no jerking when normally driving and shifting from 1st to 2nd. This along with the BMS clutch stop makes a very smooth shifting experience.

[Littlebear]

Good work, Turbo!
This will help make our big luxury cars into driving machines....

Murf

[B58 parts]

Is this piece comparable in form to what the EXX cars had ... just in a different location?

subscribing....

[TurboAra]

The picture that I took was after I drilled it. That hole was tiny!! I should have made a better write up but was just trying to finish the car because it was was taking up space in the shop.

[bavarianride]

Originally Posted by YuminNuman

Is this piece comparable in form to what the EXX cars had ... just in a different location?

subscribing....

the E39/E46 CDV is much easier to access than F-chassis.

https://www.zeckhausen.com/catalog/index.php?cPath=6562

[jparnes1]

Originally Posted by TurboAra

The picture that I took was after I drilled it. That hole was tiny!! I should have made a better write up but was just trying to finish the car because it was was taking up space in the shop.

I can't believe someone finally has info on the CDV! Way to go!
So are you saying that you drilled the hole larger and reinstalled the plate, or you discarded the plate all together? Also, did you reinstall the seals or discarded them also? Please explain clearly cuz I really want to do this!

[TurboAra]

Originally Posted by jparnes1

I can't believe someone finally has info on the CDV! Way to go!
So are you saying that you drilled the hole larger and reinstalled the plate, or you discarded the plate all together? Also, did you reinstall the seals or discarded them also? Please explain clearly cuz I really want to do this!

Gladly, once the slave cylinder is removed from the car, the disconnect point should be between the rubber hose and hardline when taken out from the car. Now put the salve on a bench with rags or paper towels because it’s going to get messy, remove the circlip holding the hardline to plastic slave, remove the hardline and watch for a cone shaped seal on the end of the hardline. Mine was stuck in the slave and I pulled it out with a pick tool, put the rubber seal on the end of the hardline in its resting spot. Now there will be a round rubber seal and below that is the restrictor. At this point i used a drill bit and began drilling but you should easily be able to pull the seal out and restrictor with a set of angled pick tools. I began drilling and as the bit was about to punch through it pulled the metal restrictor and rubber seal out on to the bit. The restrictor needs to be reused because it looks like it’s taking up space to hold the seals together. I will find out what drill sizes I used. After drilling you can push any remaining fluid from the Slave to get as much debris out then assemble drilled restrictor and seal.

You can feel a difference in driving immediately, i used to hate the 1st to 2nd shift, but it transitions so smoothly now. Clutch pedel feels less resistance towards the end of its travel. This should be done to every manual F chassis car period

F10 5 series received a separate CDV valve for the manual cars so if anybody wants to research if part number 21526785964 f10 slave cylinder will work for F30’s then that’s worth a shot. The slave used on the F30 with resistrictor is also used on 2 series, 4 series and M2,M3, and M4

[the dope steez]

Thanks for the write up and experiment! Might be worthwhile to buy a new OEM slave cylinder to do the restrictor removal and then replace the entire unit

[phat8186]

Interesting I'm wondering if this is the reason why I hate shifting from 1st to 2nd in my 6spd f30 335xi

[pjkbrit]

Awesome work turboara!!!!
Will be doing this to my 2013 335.

[Mouse]

[B58 parts]

Slave Cylinder
Product ID: 21-52-6-795-713
$72.30

Not bad .... it's not $400 or something. I'm considering. Would like some more analysis of this first though..

[kern417]

I wish I was more familiar but I can't picture where this is. Can you pull it without dropping the trans or tearing apart the interior?

[TurboAra]

The removal of the slave is easy enough once the plastic cover over the transmission is removed or pushed out the way. Remove the slave then disconnect the hydraulic hose. When you remove the hydraulic hose fluid is going to pour down like a stream. Bmw says to pinch the hose with pliers but I prefer to cap the hose or you can do what I did and that’s push the clutch pedal in the downward position to stop fluid from flowing (doing this will cause air to enter when pedel is released but we will be reverse bleeding later) slave is only held in by 2 nuts and is pretty easy to get to, for the top nut, I used a series of wobble extensions to get the angle I needed.

Attached shows the round seal still on the drill bit.

I used pentosin DOT 4 low viscosity, ATE also makes a good brake fluid for our cars.

Last pic is a 1 oz syringe I used to push in the fresh fluid from the slave bleed screw. Now is also a good time to suck out all the old fluid in brake resoirvoir and push in all the new fluid from the slave side.

Note: the slave cylinder is plastic and so is the bleeder screw, it takes a few turns of the bleed screw for it to open and allow fluid movement, don’t jus crack it half turn. Do not overtighten the bleeder screw! Plastic.

[MacklinUSOB]

Excellent work, this CDV has been pretty illusive, definitely putting this on the top of the mod list.

[B58 parts]

I guess .. if anyone has a non F30 slave cylinder and can take it apart and confirm that the little metal washer thing seen in figure 1 is not present .. that would help me chop the car up. I'm concerned that is some special thingy that is not a CDV.

[jparnes1]

Originally Posted by TurboAra

Gladly, once the slave cylinder is removed from the car, the disconnect point should be between the rubber hose and hardline when taken out from the car. Now put the salve on a bench with rags or paper towels because it’s going to get messy, remove the circlip holding the hardline to plastic slave, remove the hardline and watch for a cone shaped seal on the end of the hardline. Mine was stuck in the slave and I pulled it out with a pick tool, put the rubber seal on the end of the hardline in its resting spot. Now there will be a round rubber seal and below that is the restrictor. At this point i used a drill bit and began drilling but you should easily be able to pull the seal out and restrictor with a set of angled pick tools. I began drilling and as the bit was about to punch through it pulled the metal restrictor and rubber seal out on to the bit. The restrictor needs to be reused because it looks like it’s taking up space to hold the seals together. I will find out what drill sizes I used. After drilling you can push any remaining fluid from the Slave to get as much debris out then assemble drilled restrictor and seal.

You can feel a difference in driving immediately, i used to hate the 1st to 2nd shift, but it transitions so smoothly now. Clutch pedel feels less resistance towards the end of its travel. This should be done to every manual F chassis car period

F10 5 series received a separate CDV valve for the manual cars so if anybody wants to research if part number 21526785964 f10 slave cylinder will work for F30’s then that’s worth a shot. The slave used on the F30 with resistrictor is also used on 2 series, 4 series and M2,M3, and M4

You're the man! Thanks.

[jparnes1]

Originally Posted by YuminNuman

I guess .. if anyone has a non F30 slave cylinder and can take it apart and confirm that the little metal washer thing seen in figure 1 is not present .. that would help me chop the car up. I'm concerned that is some special thingy that is not a CDV.

It is def the CDV. It talks like one and walks like one. And the change in shifting after modification was what you'd expect.

[jparnes1]

If the seal and restrictor can be removed from the slave with a pick, why do you need to remove the slave at all? I can disconnect the hardline from both ends, modify the restrictor and put everything back. Am I missing something? The only reason I'm asking is because the upper bolt on the slave is pretty hard to get to. I'm working blind in a very tight space.

[TurboAra]

The trick is to use a long extension and reach it from around the trans mount area. The inlet for the slave Is crowded because it’s so close to transmission tunnel. If you can see what you are removing you can try that, but from what I saw working under there it’s pretty tight. It’s best to remove the Slave and not hard if you use the wobble extension. I’m going to put in a new poly trans mount soon so I can try and show how I got to the top nut with the extension.

[jparnes1]

Originally Posted by TurboAra

The trick is to use a long extension and reach it from around the trans mount area. The inlet for the slave Is crowded because it's so close to transmission tunnel. If you can see what you are removing you can try that, but from what I saw working under there it's pretty tight. It's best to remove the Slave and not hard if you use the wobble extension. I'm going to put in a new poly trans mount soon so I can try and show how I got to the top nut with the extension.

I did try to position an extension up there and managed to get it on the bolt head. I was more concerned about being able carry the bolt on the extension and get it back into the hole later. Any additional help would be appreciated. TIA.

[TurboAra]

Remove the bottom nut first and get the bracket off the stud, once it’s off you should be able to get 2 fingers around the top nut being able to hand tighten or loosen the nut off the threads. The slave will have a spring loaded effect but it’s not going anywhere. Now is a good time to clean the old dried grease off the end of the slave and the fork side. Use some thick grease on the end of the rod and fork