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Technical Clutch Delay Valve (CDV) removal

hard top

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hard top submitted a new resource:

Clutch Delay Valve (CDV) removal - Clutch Delay Valve (CDV; 01’-02’ non-M Z3s):

Clutch Delay Valve (CDV; 01’-02’ non-M Z3s):

This is a Clutch Delay Valve (CDV) removal and slave bleeding procedure for a 2001-2002 2.5L or 3.0L Z3. This walk-through is intended for those who need more direction and are less familiar with such DIY projects. I used a pressure bleeder, which is not required unless you wish to follow the walk-through exactly.

Please read the entire walk-through before attempting this procedure.

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Rev

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Hi David,

By slowing down the fluid it makes you take more time to change gear and so takes strain from the drive train, but it also makes gear changing gratey if you don't give it time, especially when cold. I do not race the said car nor change that quickly usually, so I can't imagine I put any strain on the box, but I find now everything is a lot smoother.

I cannot imagine that any race car would ever have one fitted, but see it as a device to save BMW from coughing up on warranty issues with boy racers.

This is from Wikipedia and explains:

A clutch delay valve is an automotive component added to the clutch system of an automobile to standardize clutch engagement speed. Its purpose is to engage the drive train of an automobile without introducing shock to the drive train components by engaging too quickly. By preventing drive train shock, CDVs also prevent an automobile's balance from being upset, which aids in handling characteristics.

Clutch delay valves operate on the principle that engagement only needs to occur at a certain rate to be efficient and that engaging at a quicker rate can damage the drive train components of an automobile. Engaging the drive train to the engine too quickly can damagedrive train parts, including the transmission, differential, half shafts, axles, and CV joints. Engaging the drive train too slowly can damage the clutch friction disc and cause clutch slippage.

Clutch delay valves operate as one-way restrictor valves that limit the volume of fluid that can move through the lines in a given time. This ensures a steady quick and firm engagement without being too fast for the drive train to handle since clutches can quickly disengage but re-engagement is damped. The clutch delay valve slows clutch engagement and was intended to reduce drivetrain shock in the event that an inexperienced driver quickly engaged the clutch at higher revs.
 

David Cullen

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Thanks for the reply Rev, I find I can still gear quickly but the lag on the engine is what puts me off...
Can this valve be bore out or does it have to be replaced? Thanks again :)
 

Rev

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I bought a replacement part from the USA. It was just the same but bored out, so I would suggest any opening of the gap will do. Even a half way house would be much better.

I'm very pleased with the gear change now over and above before.

:)
 

David Cullen

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Very good, thanks for the heads up re being able to bore it out, I will have a look soon and hopefully determine whether it can be a DIY job for people to do in the future ;-) thanks again Rev
 

GazHyde

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