Leaking clutch master cylinder

virsipe · Mon, Feb-05-2007, 06:00:42 PM

I popped the hood on my 2004 6-sp manual M3 (~29K miles) this past weekend to admire the engine and noticed that the clutch master cylinder resevoir was a bit leaky. Not so much that it was dripping, but enough that it covered the entire resevoir top and sides with fluid.

I don't race the care and have not taken it to any track events. I will be taking this to the dealer since I need to go in for the smog update anyway, but was curious if anyone else noticed this same problem before? Thanks:nixweiss:

**deilenberger** · Mon, Feb-05-2007, 07:48:27 PM

Ummm..

There isn't a seperate "clutch master cylinder" reservoir - it's a shared reservoir for brakes and clutch. Sounds as if it was overfilled.

IF you or someone else installed brake pads recently without drawing some fluid out of the cylinder that can account for it being overfilled.

FWIW - the capacity of the reservoir is such that you should NEVER have to add fluid between pad changes (unless you have a leak.)

It's designed to have enough fluid to stay above "MIN" mark when the pads are worn out. It should come back up to the "MAX" mark when the new pads are installed.

virsipe · Mon, Feb-05-2007, 08:08:36 PM

Ths same reservoir-that makes sense.

Last time I checked, it was not overfilled. Since I've not changed the brakes since getting the car and usually with more brake wear, the level declines, I am going to guess that the fluid level was not too high. It was not leaky a few months ago the last time I was under the hood checking around.

In that case, is it common to have a leak out the top of the reservoir due to excessive brake use? I've heard some mention of boil-over with old fluid when going to the track (H20 infiltration I suppose). Since I've not tracked my car, I would guess that this is not the case in which case it must be a leaky cap or something.

Anyway, I'll have the dealer check this out.

I plan to start running some of the local GCC BMW events, so I want to be sure that I am not leaking.

Mon, Feb-05-2007, 06:00:42 PM	#1
virsipe Registered User Join Date: Jan 2005 Posts: 77 Reputation: 0	Leaking clutch master cylinder I popped the hood on my 2004 6-sp manual M3 (~29K miles) this past weekend to admire the engine and noticed that the clutch master cylinder resevoir was a bit leaky. Not so much that it was dripping, but enough that it covered the entire resevoir top and sides with fluid. I don't race the care and have not taken it to any track events. I will be taking this to the dealer since I need to go in for the smog update anyway, but was curious if anyone else noticed this same problem before? Thanks:nixweiss:

Mon, Feb-05-2007, 07:48:27 PM	#2
deilenberger Moderator Join Date: Dec 2004 Posts: 13,363 Reputation: 578	Ummm.. There isn't a seperate "clutch master cylinder" reservoir - it's a shared reservoir for brakes and clutch. Sounds as if it was overfilled. IF you or someone else installed brake pads recently without drawing some fluid out of the cylinder that can account for it being overfilled. FWIW - the capacity of the reservoir is such that you should NEVER have to add fluid between pad changes (unless you have a leak.) It's designed to have enough fluid to stay above "MIN" mark when the pads are worn out. It should come back up to the "MAX" mark when the new pads are installed. __________________ Don Eilenberger AKA bellymeisterburgermeister and denilegiiiiiiiiiiiiibennnnegerieragher (but that's misspelled..) 2001 M-Coupe - TiSilver/Black - Das Boot.. 2002 M3C/6 - Imola Red/Black - SOLD 2003 525iT - Green/Tan - SOLD - replaced with Lexus 2006 Cayenne/S - Iceland Silver Metallic/Stone-steel Gray - Truckster. 2007 R1200R - Roadster, black mit/white pinstripes - the REAL BMW.. 2011 Lexus RX-350. SWMBO's new toy.

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Mon, Feb-05-2007, 08:08:36 PM	#3
virsipe Registered User Join Date: Jan 2005 Posts: 77 Reputation: 0	Ths same reservoir-that makes sense. Last time I checked, it was not overfilled. Since I've not changed the brakes since getting the car and usually with more brake wear, the level declines, I am going to guess that the fluid level was not too high. It was not leaky a few months ago the last time I was under the hood checking around. In that case, is it common to have a leak out the top of the reservoir due to excessive brake use? I've heard some mention of boil-over with old fluid when going to the track (H20 infiltration I suppose). Since I've not tracked my car, I would guess that this is not the case in which case it must be a leaky cap or something. Anyway, I'll have the dealer check this out. I plan to start running some of the local GCC BMW events, so I want to be sure that I am not leaking.