[FieldingMellish]

Very interesting stuff re. CDVs on this thread:

http://www.e90post.com/forums/showth...=164626&page=2

Particularly this link re. replacing CDVs:

http://www.zeckhausen.com/CDV.htm

MOst relevant for my experience was their description of the effects of having a CDV, and how replacing it would improve the experience of changing gears:

" No more vague, inconsistent clutch engagement. No more jerky 1-2 shifts. "

Exactly my experiece. Jerky first to second changes and vague bite point the rest of the time, vagueness doesn't really matter so much at higher speeds of course but vague it certainly is.

Anybody replaced tehir CDV here?

[willhollin]

Mate speak to Ant @ Speedreligion, he is right on your doorstep and stocks / installs them.

http://shop.speedreligion.net/modifi...alve-137-p.asp

[FieldingMellish]

Thanks willholin, actually I'll be seeing Ant next week as I'm having Black Lines fitted. I'm sure he can do teh CDV thing, but what I want to know is how many people on here have had their CDV replaced and has it helped?

[M3-FAST]

I was told previously that 325 engine models and above have this valve?

Mine had had this judder from day 1 - even managed to get BMW to fit a new clutch at 4k miles. Seemed to improve for a while but returned soon after.

Coincidentally, I had not noticed it for a few weeks, but it returned with a vengeance this afternoon, juddering badly 3-4 times when pulling from standstill.

[PeteJ]

Well mine is going in this week for the stealer to have a look at the clutch problem and I've said about the CDV however the tech seemed to think it isn't fitted to the 320d.

He said he would double check either way, however will let you all know for sure when it goes in on Friday

[roofer]

Bear in mind the CDV also extends the life of the dual mass flywheel. Its a type of shock absorber.

[NFS]

I've never had a problem with the CDV.

You can't 'feel' the bite point as such, but you can tell where it is all the same.

Problems with jerky 1st - 2nd shifts go away with time and are more to do with the stiffness of the box than the cdv.

[Ant397]

Originally Posted by NFS

I've never had a problem with the CDV.

You can't 'feel' the bite point as such, but you can tell where it is all the same.

Problems with jerky 1st - 2nd shifts go away with time and are more to do with the stiffness of the box than the cdv.

You may never have had a problem with it consciously, but it has always been there interfering with your every gear change and use of the clutch, you have just adapted to work around it... It is always limiting the engagement of your clutch and when removed gives you back 100% control and feel.

I’m not saying everyone needs to do the modification, but everyone deserves the right to control their clutch as they see fit... and I would be very surprised if you didn’t prefer the drive of your clutch with this modification carried out...

I appreciate your views NFS and I would like to offer you the chance to see what difference a modified CDV does and then ask you to write about your findings for everyone to read and we will fit it for you F.O.C. If you prefer your car with the CDV (which I highly doubt) then we will put your car back to as it was before with no cost. Obviously you will have to re-adapt to the change, but it is for the better and the biting point is greatly enhanced, I promise.



Anthony.

[NFS]

Originally Posted by Ant397

You may never have had a problem with it consciously, but it has always been there interfering with your every gear change and use of the clutch, you have just adapted to work around it... It is always limiting the engagement of your clutch and when removed gives you back 100% control and feel.

I’m not saying everyone needs to do the modification, but everyone deserves the right to control their clutch as they see fit... and I would be very surprised if you didn’t prefer the drive of your clutch with this modification carried out...

I appreciate your views NFS and I would like to offer you the chance to see what difference a modified CDV does and then ask you to write about your findings for everyone to read and we will fit it for you F.O.C. If you prefer your car with the CDV (which I highly doubt) then we will put your car back to as it was before with no cost. Obviously you will have to re-adapt to the change, but it is for the better and the biting point is greatly enhanced, I promise.



Anthony.

Thanks for the kind offer Ant, if you were a little bit closer to me I would probably take you up on it - if only out of curiosity.

Unfortunately, I don't get up to Manchester much though.

You may well be right that I am simply used to the CDV. I had 4 manual e46's before my current car so It's perfectly possible that I have just adapted to it.

I will admit that I did find the changes in the 330i a bit tricky at first. I particularly remember struggling with clutch control when going over speed bumps. Pretty sure that this was due to the CDV and I do remember 'lurching' a bit as a result.

I don't find this to be a problem now though, which probably proves your theory.

[PeteJ]

Well I have just phoned 2 local dealers and both have never heard of this fault! Seems we are the only ones! Mine is still booked in with my normal dealer for Friday however even they were't aware of this 320d feature!

One slight worrying comment by one dealer (not my usual one) was that it would be 3 hours labour charges should it turn out that they can't find a fault or it was "driver" related then I would be in the line for a £100+vat per hour labour bill!! Ouch!

None of them could confirm if the 320d had the CDV.

If no joy from my dealer on Friday, I think this might be a letter to BMW.

[FieldingMellish]

Originally Posted by PeteJ

One slight worrying comment by one dealer (not my usual one) was that it would be 3 hours labour charges should it turn out that they can't find a fault or it was "driver" related then I would be in the line for a £100+vat per hour labour bill!! Ouch!

Heh. I have experienced this syndrome. When they can't find and/or fix the problem, they resort to suggesting that it is a 'driver issue' i.e. it is your fault. They told me it might be a 'driver issue' that my car kept cutting out, while I was doing, say, 35 mph in 4th gear. Now I may not be Sterling moss, but I'm not so bad a driver as to make a car stall while driving steadily along at speed.

[roofer]

None of them could confirm if the 320d had the CDV.

All BMW's with the DM Flywheel have a cdv. This includes the 320d. They call it the lock valve.

[FieldingMellish]

Originally Posted by roofer

All BMW's with the DM Flywheel have a cdv. This includes the 320d. They call it the lock valve.

So are you happy enough to keep your CDV/lock valve, Roofer? I am considering getting rid of mine, I have to say.

[roofer]

Originally Posted by FieldingMellish

So are you happy enough to keep your CDV/lock valve, Roofer? I am considering getting rid of mine, I have to say.

I have a 335d, auto only. I drilled the CDV out on a 528 (E39) i had once, heavy launches, and brutal clutch use will destroy the Flywheel eventually, which will cost aprox £1200 to replace. I would leave well alone if you intend keeping the car for big mileage.

[FieldingMellish]

Point taken, but i would love to get rid of that jerky, lurching feeling you get when trying to change gears reasonably quickly. The only way I can start off from teh lights, and not jerk, is to let the clutch up really slowly, meaning it takes ages to get up to speed.

Ideally I'd like to try someone else's car who's had teh CDV replaced and see how the clutch feels.

[roofer]

The cdv controls the flow of fluid to the slave cylinder, so regardless of how quick you lift the pedal, it will always engage at its own speed.

I would try bleeding it with high grade fluid, see if it helps. I had an E46 330 with a similiar issue, bleeding it through had a marked improvement, and cost a tenner.

[NFS]

Originally Posted by FieldingMellish

The only way I can start off from teh lights, and not jerk, is to let the clutch up really slowly, meaning it takes ages to get up to speed.

Ideally I'd like to try someone else's car who's had teh CDV replaced and see how the clutch feels.

I don't have any problem letting in the clutch quickly and I still have the CDV. I slow down at the point of engagement, but that's how I have always shifted gear to avoid 'slapping' the plates together.

I reckon roofer may be on to something with the bleeding suggestion.

[G33]

what grade fluid do u guys recommend?

[FieldingMellish]

I can't say I slow down at the point of engagement, because I can't feel one! But (at low revs) I'll get a jerky change if I don't do it slowly. So rather than allowing me to let the clutch up quickly, in fact it slows me down!

[NFS]

Originally Posted by FieldingMellish

I can't say I slow down at the point of engagement, because I can't feel one! But (at low revs) I'll get a jerky change if I don't do it slowly. So rather than allowing me to let the clutch up quickly, in fact it slows me down!

There isn't much feedback through the pedal, but in my car I can definitely still feel where the bite is.

[FieldingMellish]

Hmmm, in mine I would say it's less of a 'bite', more of a 'nibble' :-)

The vagueness doesn't matter at high speeds/revs, but leads to prolonged clutch releases at lower speeds, so it's most apparent when changing up/down through first, second, and third.

[PeteJ]

although i get some judder moving off lights, i don't get it all the time. I really get the judder when doing a hill start. If I use just the clutch to move off, i get a very slight judder, however if I apply any power at all the car judders really badly