I have been researching this a little bit and the out come...
Diagnosis - Jerky movements when changing up through the gears & not being able to release all of the power when wanted.
Slow clutch engagement on E36, E46, E39, and E53
Many owners of the E36, E46 3-series, E39 5-series, and Z8 cars have noticed that they will get an excessive amount of clutch slippage and poor clutch engagement feel. This problem is most noticeable in situations calling for hard acceleration or quick shifting.
The cause is an added check valve (BMW refers to this as the "E36 Lock Valve (21)" & "E46 Lock Valve (15)" and we call it a CDV) in the clutch hydraulic circuit that 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 build-up in the flywheel leading to early failure.
...and also on E36 M3/Z3M 3.2l with a aftermarket lightweight flywheels!
A little-known detail about the 1996-1999 M3/MZ3 3.2l (including Euro cars) is that they too have this part. Similar to the affliction of the E46 and E39, except this valve seems to affect cars with aftermarket lightweight flywheels ever so more than those that have standard flywheels. Due to the quick-revving nature of these setups, the slow-down of the check valve causes momentary excessive clutch slippage. A particular example is a "power shift" where the revs hang for a moment before fully engaging. E36 M3s with the 3.0l (1992-1995) engine do not have this part - Most other E36 do have the CDV - Listed below (thanks to Pangster)
Click for larger image - Below E36 & other models possible locations of the Lock Valve (CDV)
Click for larger image - Below E46 & other models possible location of the Lock Vavle (CDV)
This is what a CDV looks like - image below
Removal of the valve in these cars results in very crisp and firm shifts. With a lightweight flywheel, the engagement is so positive and quick that passengers are pushed into the seat with greater force than ever before.
The good news is this valve can be removed from the system with no additional parts required. The check valve is threaded into the clutch slave cylinder with an end that matches the end on the metal hydraulic line so all that needs to be done is remove the valve assembly and reinstall the line to the slave cylinder. Bleed any air out of the hydraulics and you are done.
With a Big thanks to Pangster! Here is a link to show E36, E46 & Z3 models with the CDV
Hope this is useful to any one with any of these models of BMWs
Thank you to those below...
Compiled with information contributed by Paul Dzimian and Rob Levinson - EDITED by Devil318iS
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