Clutch self-engages at stop sign

Hi,

I'm having a clutch problem and am looking for a bit of diagnostic help.

I think most clutch problems are beyond my ability, but I would like
to know what to expect if I take it in for service.

This started happening in the last week or so.

I come to a stop sign. I push the clutch in all the way and hold it while I brake
to a stop. When I proceed to let the clutch out, engagement appears to be at the "bottom"
of the foot travel instead of in the middle where it normally is. If I continue on, I shift through the gears and things feel fine with engagement at the normal position.

In some cases, I have had the peddle to the floor and the clutch has self-engaged
and the engine dies.

It seems to be dependent on how long I hold the peddle down. I can still drive OK
if I change my stopping procedure to: shift to neutral, brake to stop, clutch in and go.

It does seem to help if I "pump" the peddle, maybe.

I have replaced the clutch hydraulic fluid (brake fluid) and that did not fix the problem.

 

I crawled under the truck and put a measuring tape on the distance from a fixed point to the position of the moving bit while my lovely assistant pushed down on the clutch peddle. About 20% of the time the thing would go to full length and then fall back about halfway to resting. I think that means either my master cylinder or slave cylinder are leaking internally and unable to hold pressure against the spring.

That happens to be something I think I can fix. Now to order new ones and get them installed.

 

That's what it sounds like. Keep in mind that a slave will leak only to the outside world and be visible while the master can leak internally and not "show".

 

Sounds like you did a good job diagnosing. I would put money on the slave cylinder because it is more exposed to the elements, but you can at least check if the master cylinder had a major failure by looking around where the pedal connects to it, is it greasy or have pooled oil.

 

I would just replace both and be done. They aren't that expensive to replace.