Intermittent clutch issue

[Curious Hound]

Twice now, in the past month, I have had an issue with my clutch. After the truck has been sitting for several days, the clutch will engage too soon the first time I use it. Specifically; I get in, push clutch, pull shifter out of gear, start engine, shift into gear, then clutch engages as soon as I start to pull my foot back. Not in middle of travel like normal.

If I pump the clutch a few times, all is normal. It is normal while I drive and will even be normal all day and the next day. Only happens when the truck sits unused for several days.

1993, 3.0L, M50d, 1354e, 165k miles, OEM original clutch system as far as I know.

I haven't found any fluid leak yet. But i have had to top off the reservoir once. So if there is a leak, its probably at the slave. Is this a sign that I should be ordering a new master/slave cylinder kit? Seems to me that if I somehow got air in it, the problem would be continuous.

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[RonD]

If reservoir is going down then there would be a leak
But that doesn't mean air will come in.

When truck sits(clutch pedal up)........and leaks, lol, the fluid in the reservoir keeps system air free as it flows in, valve at master is open allowing fluid from reservoir to flow in.
When clutch pedal is pushed down valve is closed.

You may be getting some slight negative pressure in the Reservoir, make sure cap's vent passes air

So when you press down the first time on the pedal slave extends but not fully, so clutch engages lower on the pedal.
Use of pedal gets fluid back in balance, no pressure difference

 

[Curious Hound]

Thanks, Ron. That makes sense. I haven't done much clutch work. So i didn't really know what is going on internally with the master cylinder at different points in the operation.

I guess I'll be spending a few minutes on Rock Auto tomorrow.

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[scotts90ranger]

Sounds like air in the slave cylinder, put the pedal to the floor and slip your foot off a couple times, when the ol '91 explorer I had had a bad slave cylinder that was a normal occurrence...

 

[Curious Hound]

Thanks, Scott. But since the reservoir hasn't gone completely dry, I suspect it is more along the lines of what RonD explained.

Anybody reading this know how easy it is to replace rear main seal on a 3.0L? If I get in there to replace the clutch AND find a rear main seal leak, Is it a simple seal replacement? Or does a bunch of stuff have to come off? ie; oil pan, bearing cap, stuff like that. (I know everything has to come off the end of the crank shaft.) I suspect I may have a minor leak there also. My brief Google search indicates that it's not a bad job.

 

[scotts90ranger]

doesn't have to be empty if it sucks some air in past the shaft seal on the piston...

I imagine it is a modern seal not a 2 piece rear main, should be fairly easy once the flywheel is off but of all the RBV's I've had none have been a 3.0L