Clutch sticking What a interesting experieance

[Jaime]

I have a 1967 MCI-5a with a Spicer 4 speed.
       As I pulled off the highway and exited at Seal Beach, Ca I depressed the clutch rolling to a stop at the end of the ramp. When the light turned green I eased off the clutch nothing, then I started to role back. I looked down at the clutch and it had not returned to the full upright position. I reached down and pulled it up and it was like popping the clutch full engaged. I continued to my final destination working the clutch up and down bottom and top of my foot to lift it. Upon arrival to my destination and parked it seemed to work fine. I decided to block it and grease everything just in case it was dragging somewhere.  It seemed to work fine when I left but I grabbed a bungee cord just in case. Sure enough as I am driving out of LA and it sticks again I grab the bungee and tie it with tension to the steering column and it works perfect. I checked the return spring it seems to be OK. I find it weird that it seems to be OK when parked.
      So now for the question is. Any idea of what or where to check next. I am parked for a few weeks and would like to fix it. It is a 1967 maybe the spring is getting weak, I guess I could order a new one. I am going to break out the manual to see If I am missing something.

[buswarrior]

Get an assistant, coordinate carefully via radio to prevent crushed fingers...

apply grease to each and every fitting, both with the clutch pedal up and down.

You are getting ALL of them?

And work it work it work it.

No point in adding springs until you are SURE there is grease all the way around the contact points in each and every joint, connection and fitting that has movement.

happy coaching!
buswarrior

[Jaime]

Great idea I had not thought about greasing everthing under load, I do have an assistant. I will check to make sure I get them all both front and back.

[gus]

Your clutch linkage may be worn out. GMs have a bellcrank on the engine bulkhead of cast Al that wears out and makes the clutch do weird things.

Don't know if this applies to your off-brand bus though!!!

[Fredward]

The MC-5 has an air cylinder mounted on the side of the transmission that reduces the force required to hold the pedal down. Its possible the cylinder is not getting air and maybe sticking. While you are under there, check to see if that cylinder is working smoothly. Or maybe its out of adjustment and that cylinder is going over center and holding the clutch in the disengaged position?

If I recall correctly, clutch springs are what returns the pedal to the engage position. Any other springs would merely be to help hold the pedal in the engaged position or keep it from rattling.
Fred

[bevans6]

There are a couple of things to check, in addition to the lubrication (don't forget the throw-out bearing, it can be lubed externally as well).  First thing is the return spring, which is located up front under the drivers area.  It is what pulls the pedal up into the free play position, top of travel.  It's a coil spring about 8" long attached to the pedal linkage.  The other spring in the system is of course the clutch cover springs, which are a whole bunch of little coil springs inside the clutch cover that press on the pressure plate.  They are what you release when you push down on the clutch, basically.  The second thing is the air assist cylinder lever adjustment.  The air assist cylinder presses against a lever, and as you press down on the pedal the lever rises and creates an angle for the air assist cylinder to press against.  The cylinder and the lever must be directly in line when the clutch is released, so that the cylinder pressure is in line and not pushing up (makes sense when you see it).  That angle is adjusted with a 1/2" bolt (3/4" wrench) down under the transmission where the linkage is located.  The final thing is the clutch free play.  That is adjusted with a 2" diameter hand-wheel that is kind of under the alternator.  That adjusts the free play in the system.  What you do is pull up on the hand-wheel to engage it, turn in all the way down (clockwise) to take out all play, then turn it exactly one full rotation counter-clockwise to set the free play.

If this happened suddenly, probably the return spring under the floor up front broke.  The thing you hope didn't happen is the driven plates inside the clutch broke and are hanging the clutch up on the input shaft splines, not allowing it to return or engage properly.  That would be bad...

HTH,  Brian

[Jaime]

Thanks all I will be checking this weekend if its not raining. Iwill Let you know what I find.

[Jaime]

Well, I worked on the clutch issue over the weekend. I was not able to get he clutch to duplicate the problem. I did lubricate all the pivot points. I also adjusted the front  return spring to increase tension on pedal. I removed, cleaned and inspected seals on clutch air assist cylinder, everything looked fine.  I was unable to find a way to lubricate the throwout bearing. As a side note pulling that spare out of the front to get in there and inspect is a tough job. I did adjust the the handle wheel adjustment to the correct postion.

[bevans6]

The throw-out bearing grease port is just above the cross-shaft on the bell housing that the clutch linkage moves to move the throw-out bearing.  There is supposed to be a grease flex line going from the bell housing to a panel under the alternator with a remote grease nipple.  There is (or is supposed to be) a flex line inside the bell housing to connect between the other side of the grease port on the bell housing and the throw out bearing.  Greasing that lubricates both the bearing itself, which spins when engaged to the clutch, and the bearing carrier which slides along the input shaft housing.  If it goes dry, all sorts of sticky things can happen...

Brian

[Jaime]

Thanks for the clarification of the through out bearing. I checked and the grease zert labeled for the throughout bearing and it is terminated not conected to any line. after removing an access plate on the bottum side of the bell housing I was able to see the bearing but was unable to find anywhere to grease, Could be an issue I guess.

[bevans6]

I have a gearbox out in my shop, I will take a couple pictures today.  I know that simple lack of maintenance killed the TO bearing in my bus, so I think it's a little unknown that you can even lube it. 

Brian

[Jaime]

Took it out for a spin the other day issue and the clutch seems to still be sticking at the point of engageing. the clutch actually seems easier to depress then it used to. I am leaning toward an issue with the throughout bearing not sure, any other advice.

[rgrauto]

 While I was adjusting the air cylinder on my clutch,trying to make it easy to push, I  had the same problem.  I adjusted the air cylinder stop bolt up too high. The air cylinder  with clutch full out should be in a straight line with retaining pins. If you look at it you will see how it works, HTH , Glen

[Jaime]

Thanks rgrauto I will look at that to see if it is the issue. I will be moving in about a week hopefully I can do it before then.