Clutch Issue in Zetor 5211?

[slingworks]

Ok, I am a little puzzled here....

I have a Zetor 5211, one of the last commie built tractors. Runs great. Very low hours. I replaced all the brake/clutch/master cylinders etc when I bought it 10 years ago.

Now, lately it's acting up and I'm puzzled. The Clutch works then doesn't work. It will work just fine, engaging/disengaging etc and then on some random note when you press the clutch in, it wont engage when you let the clutch out. It's as though you're holding the clutch pedal down. If I let it sit for a while and try again it works just fine. No slippage. No way it could be worn out (low hours). All hydraulics work great that control it...

PTO works fine as well as the lift when I can't get the tractor to move. PTO clutch appears to work just fine.

Only thing I could think of is maybe the disc is 'binding" on the input shaft somehow? It's a dual clutch tractor....

I do keep the TO bearing lubed through the little inspection port as required....

Any thoughts?

 

[Bayfisher]

are u sure the HNL range selector isnt being bumped when boarding/unboarding or during
operation of the tractor, look at all the detent valves and springs on top plate, u may have to
pull top plate off and look for worn damage inside, is the trans fluid contaminated/milky
looking.

 

[pycoed]

Ok, I am a little puzzled here....

I have a Zetor 5211, one of the last commie built tractors. Runs great. Very low hours. I replaced all the brake/clutch/master cylinders etc when I bought it 10 years ago.

Now, lately it's acting up and I'm puzzled. The Clutch works then doesn't work. It will work just fine, engaging/disengaging etc and then on some random note when you press the clutch in, it wont engage when you let the clutch out. It's as though you're holding the clutch pedal down. If I let it sit for a while and try again it works just fine. No slippage. No way it could be worn out (low hours). All hydraulics work great that control it...

PTO works fine as well as the lift when I can't get the tractor to move. PTO clutch appears to work just fine.

Only thing I could think of is maybe the disc is 'binding" on the input shaft somehow? It's a dual clutch tractor....

I do keep the TO bearing lubed through the little inspection port as required....

Any thoughts?

I agree it sounds like there is some binding on the splines of the shaft. Try spraying some brake & carb cleaner, ideally with a tube nozzle, onto the shaft through the inspection port? Work the clutch pedal up & down a lot & keep respraying until you think you have cleaned up the splines. I can't see how it might be related to the HNL selector, since that is a purely mechanical selection of cogs in the gearbox behind the clutch housing?

 

[rScotty]

I'm thinking about just how a throwout bearing pushes a clutch. Now even if the pushing is done hydraulically, there still has to be a fairly stout return spring on the throwout mechanism to insure that the throwout bearing moves away from the clutch and stays there. I'd sure check that spring... although without any great hopes because just the rotation of the clutch should kick the throwout mechanism back.

I have seen friction disks get some corrosion that keeps their splines from sliding on the transmission shaft splines and then the pressure plates can't squeeze the disk properly... And I've seen pressure plates not able to slide toward each other because their guide pins got corroded....
And I've seen tractors sit so long that their friction plates stuck to the pressure plates and then it doesn't disengage well and slips both. And I've seen pressure plate springs rusted until they failed
But all of those are not common. They are caused by rust and it takes a lot of rust because the clutch pressure springs are so strong that they can overcome minor corrosion.

Of course this is a older tractor - a 5211 could be 30 years old and be made in Czech years before that - and he says also low hours .... so it is a possibilty. Particularly if it sat too long. Maybe in a humid atmosphere?

So I'm stumped for now for a solid diagnosis. What I might do in this case is get through that inspection hole with a flexible camera - less than $100 now - taped to a long nozzle and some WD40 and see if I can find some corrosion to oil. Or just have a look around.

Still doing astronomy? Or was that the old owner?
rScotty

 

[slingworks]

Thanks for the replies gents. I am somewhat stumped still....
Actually this tractor has done this for a few years now. When I take off the inspection plate and look down in there, everything looks for lack of a better word, new. Nothing is rusted anywhere I can see. I've always kept it oiled via the lube port there. I've not broken the tractor in half, hopefully I won't have to anytime soon. What I dont get is the randomness of it...Tractor was built in 1987 (or at least the casting on the trans is dated). 411 hours total.

I'm guilty of nearly all of those hours. I bought it 10 years ago with only a few on it. It had sat in a heated garage for 25 years. I guess the original owner bushogged with it 2 or 3 times. and lost interest.

I plowed and did some disking last week. worked like a champ for a few hours, then....nothing. Gave up, went and ate lunch and back to work....worked as normal. I've used it for small plowing/hay, grading, etc. It's a Low Profile 5211.

The HNL selector was the first thing I checked the first time it acted up on me. It's basically limp and you can tell it is w/o power to it when this situation happens. (The pto clutch/hydraulics work just fine during the lack of power to the wheels).

Trans fluid/hydraulic oil could probably use a change. Think that would make any difference?
The fiberoptic camera actually sounds like a good idea.

 

[pycoed]

Thanks for the replies gents. I am somewhat stumped still....
Actually this tractor has done this for a few years now. When I take off the inspection plate and look down in there, everything looks for lack of a better word, new. Nothing is rusted anywhere I can see. I've always kept it oiled via the lube port there. I've not broken the tractor in half, hopefully I won't have to anytime soon. What I dont get is the randomness of it...Tractor was built in 1987 (or at least the casting on the trans is dated). 411 hours total.

I'm guilty of nearly all of those hours. I bought it 10 years ago with only a few on it. It had sat in a heated garage for 25 years. I guess the original owner bushogged with it 2 or 3 times. and lost interest.

I plowed and did some disking last week. worked like a champ for a few hours, then....nothing. Gave up, went and ate lunch and back to work....worked as normal. I've used it for small plowing/hay, grading, etc. It's a Low Profile 5211.

The HNL selector was the first thing I checked the first time it acted up on me. It's basically limp and you can tell it is w/o power to it when this situation happens. (The pto clutch/hydraulics work just fine during the lack of power to the wheels).

Trans fluid/hydraulic oil could probably use a change. Think that would make anyhh difference?
The fiberoptic camera actually sounds like a good idea.

Ah! If the HNL lever is limp then have another look. You should definitely have some feel as you move from H-N-L and back. There is a pin that connects the lever to the shaft that is notorious for dropping out. Yours may be partially out & occasionally sliding out, then back in?
It happened last year on mine - it's a very simple fix to replace the pin with a roll pin or in my case a newly turned pin + loctite.If you have a cab it is a bit of a potch to get at since the cab floor & foot throttle pedal have to come out to get access. Floor is easy enough but pedal mount was seized to floor on mine which has lived outside all its life (40 odd years).
If the pin is definitely OK, then as Bayfisher suggested, you need to look at the detents under the top cover - not too bad to do when the floor is already out.