Dirty Fluid-Master Cylinder?

elerner61 · 12-08-2020, 08:56 AM

Car will be 14 years old in May, has 82K miles. Last November upon changing/bleeding the brakes/clutch (2 year cycle) I noticed the fluid was pretty dark. Hadn't seen that on previous 2 year changes. Fluid is now a year old and I can see that it's getting dark again. I'm thinking that the seals in the master cylinder are on their way out. Has anyone else had to swap out their master cylinder?

One thing that's making me pause on this is that over the past two years I've gone through periods where upon startup and a cold motor, the clutch pedal throw has had a "hitch" in it, an inconsistency I could feel as I let up the clutch. It would go away once the motor was warmed up. That inconsistency has gone away for months...and then come back two times. It currently is in the gone away stage. I bought a clutch master and slave in preparation to swap them out but when the problem went away I held off on it (plus, swapping the clutch master seems like a nasty job, under the dash...brake fluid dripping down forearms..just great). If it's the clutch master cylinder seals that are going, could that travel to the fluid reservoir and be causing the dirty looking fluid?

Interested in experiences and thoughts.

elerner61 · 12-14-2020, 01:37 PM

I'll hit this one more time. Truly wondering if dirty fluid from seals in the clutch master cylinder could be making its way back up to the main brake/clutch fluid reservoir.

elerner61 · 12-16-2020, 01:03 PM

I spoke with a friend of mine who is a professional mechanic, he maintains a collector's small but valuable stable of cars (McLaren F1 is one). He said that it's doubtful that the debris I'm seeing in the reservoir is from the clutch master cylinder. The fluid doesn't travel that much. It is more likely from the brake master cylinder. Since replacing the brake master cylinder is an easier job than the clutch one, I'll probably do that over the winter (and the coolant expansion tank at the same time since that has to come out as well).

12-08-2020, 08:56 AM	#1
elerner61 Major 157 Rep 1,107 Posts Drives: '07 Z4M Roadster Join Date: May 2011 Location: Mount Kisco, NY iTrader: (0)	Dirty Fluid-Master Cylinder? Car will be 14 years old in May, has 82K miles. Last November upon changing/bleeding the brakes/clutch (2 year cycle) I noticed the fluid was pretty dark. Hadn't seen that on previous 2 year changes. Fluid is now a year old and I can see that it's getting dark again. I'm thinking that the seals in the master cylinder are on their way out. Has anyone else had to swap out their master cylinder? One thing that's making me pause on this is that over the past two years I've gone through periods where upon startup and a cold motor, the clutch pedal throw has had a "hitch" in it, an inconsistency I could feel as I let up the clutch. It would go away once the motor was warmed up. That inconsistency has gone away for months...and then come back two times. It currently is in the gone away stage. I bought a clutch master and slave in preparation to swap them out but when the problem went away I held off on it (plus, swapping the clutch master seems like a nasty job, under the dash...brake fluid dripping down forearms..just great). If it's the clutch master cylinder seals that are going, could that travel to the fluid reservoir and be causing the dirty looking fluid? Interested in experiences and thoughts.
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12-14-2020, 01:37 PM	#2
elerner61 Major 157 Rep 1,107 Posts Drives: '07 Z4M Roadster Join Date: May 2011 Location: Mount Kisco, NY iTrader: (0)	I'll hit this one more time. Truly wondering if dirty fluid from seals in the clutch master cylinder could be making its way back up to the main brake/clutch fluid reservoir.
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12-16-2020, 01:03 PM	#3
elerner61 Major 157 Rep 1,107 Posts Drives: '07 Z4M Roadster Join Date: May 2011 Location: Mount Kisco, NY iTrader: (0)	I spoke with a friend of mine who is a professional mechanic, he maintains a collector's small but valuable stable of cars (McLaren F1 is one). He said that it's doubtful that the debris I'm seeing in the reservoir is from the clutch master cylinder. The fluid doesn't travel that much. It is more likely from the brake master cylinder. Since replacing the brake master cylinder is an easier job than the clutch one, I'll probably do that over the winter (and the coolant expansion tank at the same time since that has to come out as well).
	Appreciate 0 Quote