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Discussion Starter #1 (Edited)
A lot of interest was generated lately when we made it widespread knowledge that the E36 M3 (and early standard E46 3-series) was equipped with a "lock valve" device that restricts clutch slave cylinder speed, making for mushy clutch engagement and slipping when shifting/clutching very fast.

According to the ETK, the E46 M3 is not supposed to be equipped with this part.

This is the interesting thing: a local E46 M3 owner recently reported that his car did indeed have the lock valve, and removal resulted in the nice crisp shifts that one should expect in the M3.

Details on this part and how to remove it:

http://www.uucmotorwerks.com/html_techtip/techtips/check_valve.htm

For those of you that have the opportunity, please check the slave cylinder in your M3 to see if it is present. The slave cylinder is located on the driver's side (LHD cars) of the transmission, roughly halfway up the side and about in the middle of the length.

Please post if you find this part.

If it is there, it will be found in one of two locations (both very close).

Here:



or here...



- Rob Levinson
 

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who is the ETK and what year was that M3 that had it?

I find it hard to believe that my year M3 (2003) has that part b/c I have no problem launching hard and making crisp shifts.
 
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Discussion Starter #3 (Edited)
maynardc said:
who is the ETK and what year was that M3 that had it?
ETK is not a "who"... it's a "what". ETK is the Electronischer Teilekatalog, or EPC - Electronic Parts Catalog. It is the official BMW database of parts information that every BMW dealer uses. You can buy one of your own at http://www.koalamotorsport.com/mall/etk.asp



The M3 that had it was either a 2001 or 2002.

maynardc said:
I find it hard to believe that my year M3 (2003) has that part b/c I have no problem launching hard and making crisp shifts.
Lots of E36 M3 owners said the same thing. Then they removed the valve and experienced the difference.

Like I said, the E46 M3 is not supposed to have it, yet this one did.

No need to guess - just check if you have a chance.

- Rob
 

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Rob, are you familiar with Dave Zeckhausen's drilled out CDV's? It replaces the CDV with a drilled out one, which both prevents stripping the threads if you just bypass the unit (I gathered from Dave that this was an issue), and keeps it looking stock in the event of a warranty issue. While the CDV being drilled out/removed would not cause a problem - we all know how dealers love to place blame on things so they can get their full shop rate vs. the 80% rate that warranty work pays.

-Dan





Rob Levinson * UUC Motorwerks said:


ETK is not a "who"... it's a "what". ETK is the Electronischer Teilekatalog, or EPC - Electronic Parts Catalog. It is the official BMW database of parts information that every BMW dealer uses. You can buy one of your own at http://www.koalamotorsport.com/mall/etk.asp



The M3 that had it was either a 2001 or 2002.



Lots of E36 M3 owners said the same thing. Then they removed the valve and experienced the difference.

Like I said, the E46 M3 is not supposed to have it, yet this one did.

No need to guess - just check if you have a chance.

- Rob
 
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Discussion Starter #5
BFP said:
Rob, are you familiar with Dave Zeckhausen's drilled out CDV's? It replaces the CDV with a drilled out one, which both prevents stripping the threads if you just bypass the unit (I gathered from Dave that this was an issue), and keeps it looking stock in the event of a warranty issue. While the CDV being drilled out/removed would not cause a problem - we all know how dealers love to place blame on things so they can get their full shop rate vs. the 80% rate that warranty work pays.

-Dan
I am aware of it, and it is definitely a good idea for the reasons you listed. I have not had any problems with stripping the threads, but I suppose anything is possible.

I would be really surprised if a dealer could reasonably claim removal of the CDV caused some failure, and particularly because it is simply so difficult to see... but again, anything is possible.

On the E36, most of them are beyond warranty at this point, so it is not a concern for those cars.

- Rob
 

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Yeah, I hadn't actually heard of anyone stripping the threads either, but DaveZ mentioned it as a risk.

In any event, good call on your part with this issue. I'm going to check my friends' M3's and let you know what I find.

-Dan

:thumbup:



Rob Levinson * UUC Motorwerks said:


I am aware of it, and it is definitely a good idea for the reasons you listed. I have not had any problems with stripping the threads, but I suppose anything is possible.

I would be really surprised if a dealer could reasonably claim removal of the CDV caused some failure, and particularly because it is simply so difficult to see... but again, anything is possible.

On the E36, most of them are beyond warranty at this point, so it is not a concern for those cars.

- Rob
 
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Discussion Starter #8
Irrenarzt said:
Is this some kind of check valve that when drilled allows for two way flow?
It always allows for two-way flow, just at a reduced rate.

Drilling it (or removing it) makes it non-functional, so it acts as part of the hydraulic line with no restriction.

- Rob
 

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I definitely need to check for this. My M3 has a 2/01 production date and I've had the clutch slip very bad on two occasions when shifting very fast from first to second.
 

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ILLCOMM said:
it must serve a purpose ...

From UUC's link

http://www.uucmotorwerks.com/html_techtip/techtips/check_valve.htm

"is intended to slow the engagement of the clutch as you release the pedal. This constant engagement device is intended to smooth out the feel of shifts and potentially reduce the shock load on the drivetrain. The reality is it causes a high rate of wear on the clutch and excessive heat buildup in the flywheel leading to early failure. "
 

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wow, thanks for the heads up rob and all the links guys, just sent zeckhausen an email. ive always been wanting to remove the cdv from my 330xi... i brought it in twice to have it checked because it just didnt respond like the loaner non-awd cars i had driven, and now i can finally do it without having to do all the dirty work myself. i love diys, but when it comes to engine-transmission, etc parts i get nervous.
 

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interesting...
i will see if i can find it tomorrow...
 

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wow, thats some pretty interesting info there rob
now if i only had an e46 m3 to check out....hehe
 

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Another data point: I have an early RWD 328i- (12/98 production). It does not have the CDV valve.
The car does exibit the same shifting charataristics as described in many threads: stumbling on 1-2 shifts and starts.
This is the most difficult street car to shift smoothly that I have ever driven. I have owned nothing but manual gearboxes for over 25 years.
Any other ideas?
 

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I just pulled a CDV from a 2003-build E46 M3 this morning. Since the BMW documentation shows it as NOT being there, I did not replace it with a modified valve. Unlike the E39 5-Series, the E46 3-Series and E46 M3 CDV removal does not involve a risk of cross-threading because a rubber line, rather than a hard line, is threaded into it and there's enough slack in the rubber line to work with the valve missing.

For the M3, I recommend removing and discarding the CDV. For the E46 3-Series, there is some concern about warranty, since it is supposed to be there on the 320i, 325i, 325xi, 330i, and 330xi models (but not the 328i). So you should probably stick a modified valve in there if you don't want to be concerned about the issue ever coming up during a service visit. It would be hard for them to show a deleted CDV caused a failure, but it's not worth the hassle of having to challenge them if it comes down to that. Better to just not have the issue come up at all.

CDV on a 2003 BMW M3



Here's the little bugger after being removed


Here's what you will see if your M3 does NOT have a CDV


I originally thought that the occasional CDV turning up in an M3 was due to an assembly line error. However, if this was true, the M3 CDV would look the same as the ones installed in the "ordinary" E46 models. This is not the case. The M3 CDV is a unique part. And it appears that they are being installed in ALL of the new (2003+) E46 M3 models with a 6-Speed manual.

E46 3-Series CDV (left), E46 M3 CDV (right)

For lots more details on this evil device, check out my CDV page at: http://www.zeckhausen.com/CDV.htm
 
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