Removing CDV Valve
Discussion
citizen smith said:
Can anyone tell if removing the CDV valve on a 3.0 Z4 lightens the feel of the Clutch Pedal, or is it about the clutch action being more positive.
It's about the action being more positive or direct. I did the CDV delete on my E46 330i; it certainly didn't lighten the pedal on mine, just made taking off in 1st gear briskly a lot smoother.Removing the CDV is 50/50 waste of time. It makes the clutch pretty sharp, some like it, some don't. It masks a worn clutch quite well so a heavy pedal will be the clutch coming to the end of its life. Make sure you use a pressure bleeder to bleed the clutch - pedal pumping can easily flip the master cylinder seals and ruin it. Replacing a master cylinder on one of these (same as E46) is not funny at all. It's a f
king horrible job.
king horrible job. Touring442 said:
Removing the CDV is 50/50 waste of time. It makes the clutch pretty sharp, some like it, some don't. It masks a worn clutch quite well so a heavy pedal will be the clutch coming to the end of its life. Make sure you use a pressure bleeder to bleed the clutch - pedal pumping can easily flip the master cylinder seals and ruin it. Replacing a master cylinder on one of these (same as E46) is not funny at all. It's a fking horrible job.
Many thanks for comments about the removal of the CDV, the car is very low mileage car and there seems to be a lot of conflicting view's on the pros and cons of such a removal - you've seemed to have summed it up well.king horrible job. Touring442 said:
Removing the CDV is 50/50 waste of time. It makes the clutch pretty sharp, some like it, some don't. It masks a worn clutch quite well so a heavy pedal will be the clutch coming to the end of its life. Make sure you use a pressure bleeder to bleed the clutch - pedal pumping can easily flip the master cylinder seals and ruin it. Replacing a master cylinder on one of these (same as E46) is not funny at all. It's a fking horrible job.
I would disagree with this. Never heard of a single person say they didn't like the feel after it was removed. It is pretty much the most recommended mod to make on the Z4 and E46 forums. Made my Z gear change much more positive.king horrible job. Touring442 said:
Removing the CDV is 50/50 waste of time. It makes the clutch pretty sharp, some like it, some don't. It masks a worn clutch quite well so a heavy pedal will be the clutch coming to the end of its life. Make sure you use a pressure bleeder to bleed the clutch - pedal pumping can easily flip the master cylinder seals and ruin it. Replacing a master cylinder on one of these (same as E46) is not funny at all. It's a fking horrible job.
I agree with this. I’ve never removed a cdv from any of my BMWs. It seems to be an Internet “thing” to do as according to the net all manual BMW gearchanges are terrible.king horrible job. aka_kerrly said:
The delay valve is that,, it makes the clutch release slower to help mask crap driving and so everyone can pull away smoothly. If you can drive properly without slipping the clutch or treating it like an on/off switch then binning the cdv, new clutch line an fresh fluid is wonderful
So, by removing the delay valve the cars clutch operates more precisely which is good. But does it make the pedal pressure feel any lighter.My weekend toy has no driver aids baring the Steering Wheel, Clutch, Brake and Throttle pedals.
citizen smith said:
But does it make the pedal pressure feel any lighter.
Going by the laws of physics it cant as the input/output of the clutch hydraulic system remains the same, but what it does do is remove a restriction, just think of trying to squeeze a tube of toothpaste, silicon or something, if the opening of said tube is small, it takes more squeezing input to squeeze anything out, enlarge the hole and it takes less input to get the same amount out. So yes your left foot might notice a difference.Total loss said:
Going by the laws of physics it cant as the input/output of the clutch hydraulic system remains the same, but what it does do is remove a restriction, just think of trying to squeeze a tube of toothpaste, silicon or something, if the opening of said tube is small, it takes more squeezing input to squeeze anything out, enlarge the hole and it takes less input to get the same amount out. So yes your left foot might notice a difference.
Many thanks, never thought of it in that way - but that's logic for you. I'll have to give it a go. The clutch on BMWs are all pretty heavy, compared to many cars, many have a bit of judder when pulling away as well, mid 2005 to mid 2011 were really bad, if you remove the CDV the cluctch is just much easier t control.
It does give the impression of being lighter imho, I have always removed the CDV and found it so much nicer to drive.
With it still in place I find I have to sort of nanny it on its release to stop it juddering, you get used to it and work around it, but it is there on every manual BMW.
I just put mole grips on the hose either side, take out the CDV housing, push out the grommet and plug it all back in, never been an issue and takes 10-15 minutes to do.
I also use redline D4 Automatic transmission fluid in the gear box too, that makes the gar changes snap into place.
It does give the impression of being lighter imho, I have always removed the CDV and found it so much nicer to drive.
With it still in place I find I have to sort of nanny it on its release to stop it juddering, you get used to it and work around it, but it is there on every manual BMW.
I just put mole grips on the hose either side, take out the CDV housing, push out the grommet and plug it all back in, never been an issue and takes 10-15 minutes to do.
I also use redline D4 Automatic transmission fluid in the gear box too, that makes the gar changes snap into place.
gizlaroc said:
The clutch on BMWs are all pretty heavy, compared to many cars, many have a bit of judder when pulling away as well, mid 2005 to mid 2011 were really bad, if you remove the CDV the cluctch is just much easier t control.
It does give the impression of being lighter imho, I have always removed the CDV and found it so much nicer to drive.
With it still in place I find I have to sort of nanny it on its release to stop it juddering, you get used to it and work around it, but it is there on every manual BMW.
I just put mole grips on the hose either side, take out the CDV housing, push out the grommet and plug it all back in, never been an issue and takes 10-15 minutes to do.
I also use redline D4 Automatic transmission fluid in the gear box too, that makes the gar changes snap into place.
Many thanks for your input and the gearbox oil tipIt does give the impression of being lighter imho, I have always removed the CDV and found it so much nicer to drive.
With it still in place I find I have to sort of nanny it on its release to stop it juddering, you get used to it and work around it, but it is there on every manual BMW.
I just put mole grips on the hose either side, take out the CDV housing, push out the grommet and plug it all back in, never been an issue and takes 10-15 minutes to do.
I also use redline D4 Automatic transmission fluid in the gear box too, that makes the gar changes snap into place.
I wish I had known about this when I had my E46 320td and 123d - they were horribly juddery pulling away!
But I got it done on my E46 325ti and it was much better. Luckily it's already been done to my Z4, but I'll need to see if the E90 I bought last month still has one! If it does, it'll be coming off.
But I got it done on my E46 325ti and it was much better. Luckily it's already been done to my Z4, but I'll need to see if the E90 I bought last month still has one! If it does, it'll be coming off.
Mr Tidy said:
I wish I had known about this when I had my E46 320td and 123d - they were horribly juddery pulling away!
But I got it done on my E46 325ti and it was much better. Luckily it's already been done to my Z4, but I'll need to see if the E90 I bought last month still has one! If it does, it'll be coming off.
Cheers for that, will get mine done. Don't think much about the gearbox, feels a bit notchy and no better than the T5 Box in my Chim. But I got it done on my E46 325ti and it was much better. Luckily it's already been done to my Z4, but I'll need to see if the E90 I bought last month still has one! If it does, it'll be coming off.
Providing you dont let the reservoir run dry no need for fancy bleeders 
just gravity bleed when complete but clamp the clutch hose so you dont lose the res fluid and introduce air when you remove the CDV unit done lots of them no complaints 
with the car off the ground takes no more than 20 minutes start to finish and yes if the fluid is knackered then your killing to birds with one stone , its seldom changed anyway either by the bigger outfits that should know better
just gravity bleed when complete but clamp the clutch hose so you dont lose the res fluid and introduce air when you remove the CDV unit done lots of them no complaints with the car off the ground takes no more than 20 minutes start to finish and yes if the fluid is knackered then your killing to birds with one stone , its seldom changed anyway either by the bigger outfits that should know better Sardonicus said:
Providing you dont let the reservoir run dry no need for fancy bleeders just gravity bleed when complete but clamp the clutch hose so you dont lose the res fluid and introduce air when you remove the CDV unit done lots of them no complaints with the car off the ground takes no more than 20 minutes start to finish and yes if the fluid is knackered then your killing to birds with one stone , its seldom changed anyway either by the bigger outfits that should know better
Cheers for that, I am getting the car booked into my local independent in the next week or so. just gravity bleed when complete but clamp the clutch hose so you dont lose the res fluid and introduce air when you remove the CDV unit done lots of them no complaints with the car off the ground takes no more than 20 minutes start to finish and yes if the fluid is knackered then your killing to birds with one stone , its seldom changed anyway either by the bigger outfits that should know better Gassing Station | BMW General | Top of Page | What's New | My Stuff