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Q: Spongy clutch: inconsistent

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Hello, my clutch free play is constantly changing. If you consider an untouched clutch pedal at 0 and the pedal depressed completely to the floor as 100, 0-50 does nothing (spring not activated whatsoever). 50-100 is where the entire clutch/shifting gears operation occurs. Sometimes it only works from 75-100 but I am always able to shift with no problems. Sometimes when I go over a bump, the clutch will start working normally (free play from 0-100). It only operates in this way (correctly) about 10% of the time. I have not noticed any correlation between the outdoor temperature, engine temperature, or anything else that could cause this. I believe it could have something to do with the hydraulic clutch fluid being dirty or having air in the lines. Other people have said perhaps the slave cylinder (has an internal slave cylinder)? Someone else said the throw out bearing but there is no grinding or other adverse noises when driving or using the clutch. What do you think?

My car has 176000 miles.
My car has a manual transmission.

Hi. I think you have a problem with the clutch master cylinder having an intermittent problem. The clutch master cylinder is just like a brake master cylinder and the O rings in the cylinder go bad causing air to get in the system giving a spongy pedal. If the O rings are leaking a little they tend to make intermittent problems in the system. I think that some of these trucks had internal slave cylinders and others had external ones. If the slave cylinder is leaking then it would cause this problem otherwise it would cause the transmission to be hard to be put in gear. If you need assistance, a certified YourMechanic technician can come to your location to help adjust the clutch on your vehicle.

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