1989 F250 4X4 with Mazda M5OD mated to 302.

I had the transmission and clutch replaced in 2014, and with the clutch, the slave cylinder and other bits. Basically, when it as done, it was new again. I don't think the shop resurfaced the flywheel, as there was a vibration when I'd let off the gas to come to a stop. Until last week, I only put 700 miles on it since the work was done and all of that was local in town driving less than 45 mph. Last week, however, I had to drive it from my house in PA to my new home in Ohio...a 276 miles trip, drive to drive. I had originally decided to take 40 across Ohio, due to the vibration at higher speeds, but about 100 miles into the trip, the vibrations stopped and I was able to reach highway speeds smoothly and with ease. I figured that the clutch finally wore in with the flywheel, and life was good. However, when I came to the stoplight at the final off ramp, my clutch pedal didn't come back up all the way. When I took off, the clutch felt fine, but I only had half the pedal I had before. I made it to my destination, figuring I'd look at it the following morning.

The following morning, I took the truck out for a spin, and the clutch felt fine...I had 100% of the pedal again. I drove it around 50 or so miles, finally taking it out on the highway again. After 10 miles, I hit the off ramp, and was back to half clutch. The drive back to the house was around 5 miles, and by the time I got back home, I had full clutch pedal back.

I'm thinking it may be the slave cylinder again, and am not looking forward to doing it again.

Has anyone else had this happen before? If so, am I close to the cause of it?

I'm just trying to get a good idea of what it may be before my buddy and I open it up.

Sent from my SM-T820 using Tapatalk

__________________
1987 560SL
85,000 miles

Definitely bleed the system to be sure. Seems to be a short lived slave cylinder. Mine has lasted 100k miles

__________________

Chris
84 280sl
82 300d euro

Yes, sounds like the slave cylinder. But i don't think bleeding it is the fix. If it had air in the system it would act up all the time. It may be leaking internally when it gets warm. Might need a new one.

Did you get the OEM slave cylinder from the dealer? I heard thats the only way to go. My dad used to own my truck and I know he had issues a few times with the slave, which is in the bell housing on that one. Sucky.

__________________
1984 300SD Orient Red/ Palomino
1989 560SEC
2016 Mazda 6 6 speed manual
1995 Ford F-150 reg cab 4.9 5speed manual

It was one from the 'Zone. I'll check with the dealer and see what they can do for replacement. As of the past few days, it's been fine, both on and off the highway. It works as it should without complaint. I just got back from a 100 mile trip, with 90% of it being at highway speeds, and it's working fine.

If I can make it last til Spring, I'll attack it the same time that I pull the bed off for some sanding of the cab. I"m lining up a list of things to do to it come Spring, and have just moved back to my hometown, where I have a number of friends willing and able to put some sweat equity into it with and for me.

I've got good friends.

Sent from my SM-T820 using Tapatalk

__________________
1987 560SL
85,000 miles

Even if its not likely the problem bleeding takes 15 minutes. I think its worth a try and would do it to be sure. You don't even have to jack up the truck. The bleed sequence is different than some. I think it goes like pump leave pedal up open bleeder then push then close bleeder. Check the ford book I could be wrong. Transmission R&R on the other hand is a PITA.

__________________

Chris
84 280sl
82 300d euro

High moisture content in the fluid would do this. Definitely start with a thourough flush and bleed.

Was the clutch master cylinder changed?

Also before we go farther, unrelated to your current problem, there are 3 rubber plugs at the back of the shifter lid, these leak and all of your trans oil ( ATF ) will fall out. Pull them, clean then silicone them into place. Also, if you have a floppy shifter, there is a cupped washer on the shifter ball that deteriorates. The parts book lists the top one but the bottom one shows as part of the shifter lid assembly. A top washer is the same, all you have to do is back one of the shifter lid pins out just enough to change the washer. If these pins are loose in the lid, put a screw hose clamp around them so it won't fall out.

Flywheel friction surface condition will only affect starting out from a stop while the clutch is being slipped. ( RE pedal between fully depressed and fully up ) Many shops don't resurface the flywheel because it ties a bay up for 1/2 day min and customer either does not want to pay or cries it is taking too long.

This isn't related to a clutch disc needing to wear in, there are other problems.


If the slave cyl failed, it would be leaking fluid. I'm leaning more towards a failed clutch master cylinder. This fails just like a brake master cylinder to where the pedal is low. The non return is an odd issue, the master is plastic and maybe the bore is worn causing the piston to stick.

The master cyl has a small roll pin where the line attaches and the slave a "push the ring then pull the fitting out" type of attachment.



Some of these trucks ( Ranger also ) use a self adjusting _pressure plate_that tends to have issues self adjusting. Have a look at the site The Ranger Station , as Rangers use the light duty version of this trans.

Note, the clutch release bearing slave cyl is self adjusting and isn't what I'm referring to . As the clutch disc wears, the pressure plate fingers rise moving them closer to the release bearing. Due to this, the geometry changes and clutch engagement height changes. In order to maintain a consistent pedal height, the pressure plate adjusts accordingly.

It's an awful system that wears badly and leads to a dragging clutch or a "boing" when pressing the pedal. I replace the pressure plate with a standard non self adjusting one that was stock on the older trucks. There is a chance the self adjusting mechanism is coming apart but I haven't seen that occur yet.

Look up "Valeo self adjusting pressure plate". Look at post 4 , first pic , right hand pressure plate, that is a self adjusting one. The small coil springs in the area of where the diaphragm spring meets the cover are part of the self adjusting system. http://www.peachparts.com/shopforum/restoration-projects-long-term-builds/386467-c280-mercedes-could-have-built.html

Oddly enough, the clutch sorted itself out after driving around town for a few weeks, both on and off the freeway. I'm assuming there was a bind somewhere in the workings that needed to wear in...I don't know. But, it's working fine now without issue. I've put around 1500 miles on it since it exhibited the above symptoms, and feel confident in it enough to drive it back to PA to pick up my tools and camper.

Sent from my SM-G955U using Tapatalk

__________________
1987 560SL
85,000 miles

It's always good to start with a flat flywheel if it shows much wear. On the mercedes though planing the fw without shimming it will get your friction point low down by the floor.

The shimming might not be needed with the annular slaves, not sure.

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

The random vibration and pedal height makes me think pilot bearing missing or worn.