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Discussion Starter · #1 · (Edited)
Having trouble adding a clutch stop to your E46?

Midway through the 2001 model year, BMW changed the design of the clutch
master cylinder, removing the externally mounted starter interlock switch,
and incorporating it into the master cylinder itself. The result is that it
has become much more difficult to modify or bypass the starter interlock

Difficult, but not impossible.

Below is a picture of the older style master cylinder (top), and the newer
style master cylinder with the interlock with integral interlock switch
(bottom). Pictured between them is a retrofit harness.

<img src="http://www.uucmotorwerks.com/images/CDV1.jpg"

This next picture shows the new style master cylinder disassembled. At the
bottom of the "plunger" is a magnet, which is what is responsible for
telling the interlock switch that the clutch is depressed. The magnet can be
removed, or fooled with another magnet, but this will in turn also defeat
the cruise control safety interlock. Not good.

<img src="http://www.uucmotorwerks.com/images/CDV2.jpg">

Now let's turn our attentoin back to that retrofit harness. That harness
exists for one reason: there is no set cut-off date for when the newer style
master cylinder was first added to the E46, nor for when an older car should
not be equipped with it. So your dealer has the ability to retrofit the
newer master cylinder to your E46 with that plug-and-play harness.

The solution is simple, but not cheap: the older style master cylinder and
interlock switch can be retrofitted. There is no factory harness for this
retrofit, so you'd have to do the wiring yourself. Then you can perform the standard interlock modification to make your clutch stop work.

I'll be the first to admit that this is a lot of work to do simply to
install a $20 part. But UUC knows there are some fanatics who will be
interested in making the swap, and countless others who wanted to know
the real truth about why there was a problem.

- Rob
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