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I had my oil changed earlier this week, the people there told me my "clutch fluid" was low. On my first trip after the oil change (2 hour round trip) my clutch started acting weird, it wouldn't pop all the way back out. It worked enough to change gears, but I eventually drove the rest of the way home in 4th gear for fear of messing something up.

At a stoplight close to home, I had to push the clutch, and it hit the floor and didn't pop back up. I was also not able to easily remove the car from gear and it stopped right there.

I have never heard of clutch fluid before, so that sounded odd and I don't see much online about it either. I would have thought they were joking had it not been for my immediate car trouble with the clutch.

Is it normal for a clutch to run low/out of fluid or is this evidence of a potentially much larger and more expensive problem?

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"never heard of clutch fluid before" probably because the fluid for hydraulic clutches is the same as brake fluid and usually referred to as brake fluid. –  cbeleites Feb 15 at 21:13
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1 Answer

up vote 5 down vote accepted

Most vehicles with a standard transmission now use a hydraulic clutch. The clutch system consists of a reservoir with master cylinder, some tubing, and a slave cylinder. It works in a similar manner as your brakes. Pushing the pedal forces a fluid into the slave cylinder. The slave cylinder applies a force to the throw out bearing which causes the clutch to disengage from the flywheel. Under ideal conditions no topping off or service is required. A slight leak that requires an occasional topping off is not unusual in an older vehicle. As long as the reservoir has enough fluid that it doesn't draw in air you can drive it like this for quite a while. When the leak gets so bad that the clutch no longer functions it is time for a repair. The usual culprit is the slave cylinder. Replacement of the slave cylinder can be relatively simple if it is outside the bell housing. In most vehicles it is inside the bell housing which requires the transmission to be removed to affect the repair. At that point you should ask if it is time to do the clutch plate while it is apart.

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Usually, if the slave cylinder is inside the bell housing and it is leaking, you usually don't have any choice but to put a new clutch in because the friction disc will have become contaminated with hydraulic fluid. –  Paulster2 Feb 15 at 2:52
    
While it's "common knowledge" that the slave cylinder that goes bad first, my experience has been the opposite. I've seen significantly more bad master cylinders than slave cylinders. –  Brian Knoblauch Feb 15 at 14:22
    
I had the car towed to a dealership and this answer is exactly what they told me. The slave cylinder had blown and was causing the leak, they asked if I wanted to replace the clutch assembly while I had the labor already done, I said no. They called later to tell me that I didn't need it anyhow because the clutch plate had plenty of life on it, but this answer was spot on. –  leigero Feb 15 at 20:56
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