How to modify your CDV (Clutch Delay Valve)

How to modify your CDV (Clutch Delay Valve)

Postby srhutch - Thu Sep 06, 2007 8:49 am

This is the one you have all been waiting for.

I have posted this How to Do in this section to ensure maximum exposure.

This valve is from a non M Z4, although I am assuming the process would be the same, if someone want to send me a M valve, I will test.

Although this is a simple process I do not accept any responsibility for any damage to you, your vehicle or any third party if you carry out this procedure.

I would also like a couple of our members to validate this process. I know our leader has a spare one, or at least one that requires modification.

I would suggest that you do this process on a spare valve just incase you do run into trouble. There are enough Z4 owners out there that have changed this part so hopefully you could find someone who will either give you their old one or loan you one until you take yours off.

If however you wish to purchase one from your dealer the price I obtained is £7.79 + vat. There is no stock in this country so delivery would be 3-4 days.

Unfortunately, I wasn’t present when I got my guy to remove this as I thought it was going to be harder than it was and therefore left him to it. But once I have changed mine, I do intend to carry out this procedure, after which I will happily donate. I would however suggest that all owners generally modify their own to prevent any problems with comeback etc.

This is a simple process that requires no special tools other than a hammer and two drills bits of 3.5mm and 9mm NO DRILLING IS INVOLVED. If you have ever replaced a wheel bearing this should be a simple procedure.

Image
Image

Fig1. shows a sectional view of the valve, the device and principal are both simple. When you depress the clutch the piston (C) moves towards the insert (B) due to hydraulic pressure which allow hydraulic fluid around the piston due to its design, when you remove your foot from the clutch the hydraulic pressure forces the piston back which forces the hydraulic fluid through the 1.5mm diameter hole. There is no spring in the valve; the force of the hydraulic fluid alone moves the piston to its required position.

The insert does two jobs, to retain the piston, and locate and seal the rigid hydraulic pipe. As it located on a step when the insert is refitted it will be in its original location. The insert is retained only by the slight interference fit with the body so is easily removed and reinserted. The slight interference is confirmed by the fact the piston has retained most of its shape after removal, if this had required a lot of force the piston would be have deformed more before the insert was removed and would probably be flat.

The process:

Insert the 3.5mm drill bit into the end with the male thread (small bore) ensuring you insert the flat end of the drill. If you insert the pointed end you will probably damage the piston and it will then be impossible to remove successfully.

It is possible to use any cylindrical object that fits the bore with a snug fit and has at flat end to locate against the piston. A screwdriver with the end ground of may also work.

By gently tapping the drill with a hammer will push the piston and insert out of the bottom. Be aware that this will probably damage you drill bit. It would be advisable to hold the valve in a vice if possible, it does not need to be done up tight, as the hex flats will locate above the jaws and prevent movement. Doing this will allow the piston and insert free exit from the body.

Once you have removed the piston you then use the 9mm drill bit again with the blunt end against the insert and tap back into place. Ensure you insert the valve the correct way with the chamfered bore facing out. It maybe easier to use a socket if the outside diameter is around 9mm as this will have a flat end top and bottom, but ensure it will fit inside the bore before attempting to refit. Again you need to use something like this for two reasons; one is so the flat bottom locates on the flats of the insert to prevent damage to the sealing chamfer, and also to ensure the insert is inserted squarely to prevent damage to the threads.

Once you have replaced the insert you are ready to fit to your car and enjoy the smoother clutch operation this procedure gives.

Apologies for grammatical errors, spelling mistakes etc. and I look forward to your feedback.

Steve
Last edited by srhutch on Mon Jul 07, 2008 9:45 pm, edited 3 times in total.
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Re: How to modify your CDV (Clutch Delay Valve)

Postby srhutch - Thu Sep 06, 2007 10:06 am

I need to make an alteration to this post, which I will do at 13:00 today

My diagram is not 100% accurate and the alteration will show this change and makes the process easier.
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Re: How to modify your CDV (Clutch Delay Valve)

Postby sp3ctre - Thu Sep 06, 2007 11:09 am

Nice one... I will leave it here for a little while, then relocate it to "How To" in a day or so, once everyone has seen it... Thanks for your efforts :D
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Re: How to modify your CDV (Clutch Delay Valve)

Postby srhutch - Thu Sep 06, 2007 1:30 pm

As mentioned he is a small amendment

Image

After final confirmation with the guy who did this for me he confirmed that there is a step on the back end of the insert.

It is this step that has the interference fit, which makes life easy as the insert will drop into place through the bore without any problems, and just need a gentle tap to locate.
Last edited by srhutch on Tue Jul 08, 2008 1:56 pm, edited 1 time in total.
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Re: How to modify your CDV (Clutch Delay Valve)

Postby carl - Thu Sep 06, 2007 10:42 pm

I don't see what the insert does. Bear in mind you can remove the CDV in its entirety, I can't see what adverse effect leaving the insert out would do. It looks like even with the piston removed the insert is acting as a venturi.
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Re: How to modify your CDV (Clutch Delay Valve)

Postby Top pup - Thu Sep 06, 2007 11:54 pm

carl wrote:I don't see what the insert does. Bear in mind you can remove the CDV in its entirety, I can't see what adverse effect leaving the insert out would do. It looks like even with the piston removed the insert is acting as a venturi.

The insert forms part of the female fitting that the clutch pipe screws into, the taper on the insert sits agaisnt a matching taper on the male fitting.
The same fittings are used on brake pipes.
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Re: How to modify your CDV (Clutch Delay Valve)

Postby carl - Fri Sep 07, 2007 12:04 am

Aye I can see that, but the whole thing is made out of one piece of metal. Where would the clutch fluid leak to? Unless you're suggesting it would leak around the thread?

If you take the CDV out entirely, is there a similar type of female fitting on the bit of hose that goes into the other end?
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Re: How to modify your CDV (Clutch Delay Valve)

Postby Top pup - Fri Sep 07, 2007 12:06 am

srhutch wrote:The insert does two jobs, to retain the piston, and locate and seal the rigid hydraulic pipe. As it located on a step when the insert is refitted it will be in its original location. The insert is retained only by the slight interference fit with the body so is easily removed and reinserted. The slight interference is confirmed by the fact the piston has retained most of its shape after removal, if this had required a lot of force the piston would be have deformed more before the insert was removed and would probably be flat.


Mine had more than a 'slight interference fit' to say the least, but if you split the washer with a thin screwdriver or simlar it is possible to get all the pieces out of the CDV with the insert in place.
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Re: How to modify your CDV (Clutch Delay Valve)

Postby Top pup - Fri Sep 07, 2007 12:31 am

carl wrote:Aye I can see that, but the whole thing is made out of one piece of metal. Where would the clutch fluid leak to? Unless you're suggesting it would leak around the thread?

If you take the CDV out entirely, is there a similar type of female fitting on the bit of hose that goes into the other end?


The pipe that goes into that side of the CDV seals on the taper, the thread is for the fitting that pushes the pipe against the taper. It won't seal against
the thread.

If you take the CDV out the fittings each side are exactly the same and screw straight together. The CDV looks like an after thought that they simply added to an existing connection.
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Re: How to modify your CDV (Clutch Delay Valve)

Postby vaderZ4M - Fri Sep 07, 2007 1:09 am

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Re: How to modify your CDV (Clutch Delay Valve)

Postby torino - Thu May 28, 2009 4:34 pm

Top pup wrote:
If you take the CDV out the fittings each side are exactly the same and screw straight together. The CDV looks like an after thought that they simply added to an existing connection.


So can you just remove the valve without modding it?
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Re: How to modify your CDV (Clutch Delay Valve)

Postby Ian_Mac - Thu May 28, 2009 4:59 pm

Yep you can do away with it totally, that's what they did to mine .
Image
Mods so far : 3" stubby ariel, chrome exhaust tips, de-badging, clear side indicators, CDV delete, cruise, clear 3rd brake light, cup-holders, Z4M alloys. Sadly now gone!
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Re: How to modify your CDV (Clutch Delay Valve)

Postby torino - Thu May 28, 2009 5:00 pm

Right, i know what i'm doing this weekend. well that and replacing my broken spring, i'm sure they're not made like they used to be :headbang:
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Re: How to modify your CDV (Clutch Delay Valve)

Postby Z4 REX - Thu May 28, 2009 8:01 pm

I have modified the CDV myself and got it fitted but my mechanic told me that it would be more benificial to get a braided clutch hose fitted. The problem was that the end of the hose which will be the oposite to the CDV is a push-in fitting with a clip, a sort of quick release coupling so it was a bit hard to source. Eventually i found a place inthe U.S.A. that advertise on E-Bay and they had one in stock for the same price as a modified CDV. They were brilliant to deal with and delivery. By the way mine is 2.5l on a 53 plate. If you want I will send you details of the seller. I havn't fitted the new hose as yet as I am waiting for the next service to get that done the same time as the hydraulic change.
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Re: How to modify your CDV (Clutch Delay Valve)

Postby Z4 REX - Thu May 28, 2009 8:09 pm

Here is a picture of the original clutch hose with the special fitting on the left and the CDV side on the right.
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