Zetor 7745 clutch issues

[knox]

Hello,

Recently bought my first Zetor ; with some help from my local farm shop I fixed the coolant leak from Cyl #3 cylinder sleeve o-rings.

now I'm looking to make the clutch disengage reliably. Generally it works, but the gears grind unless you shift at < 1000rpm and sometimes you have to pump the pedal a few times to get the engine to stop driving the machine forward.

I tried bleeding the clutch slave cylinder but that didn't help noticably. The slave cylinder piston has 3/8" to 7/16" of travel with the clutch pedal fully depressed. Is that normal or does that indicate a problem in the hydraulic end of the clutch system?

The clutch pedal as 1/4" free play. The next 2" of travel does not affect the slave cylinder. The remainder of clutch pedal travel actuates the slave cylinder until the pedal hits the floor.

I opened the clutch inspection hatch, cleaned the plugged pipe for oiling the throw-out bearing, and removed a mouse nest as best I could. Using a stack of feeler gauges I estimated the clutch release bolts are pulling about 0.060" (1/16") with the clutch pedal fully depressed. Is that correct? Or should I tighten the 17mm lock nuts on the release levers (one turn) to get a little more clutch release travel?

Given these characteristics, any tips as to what is likely to be the root problem and where I should start with adjustments, bleeding or replacing parts??

This will be a lightly used tractor on a hobby farm so I hope to apply a quick adjustment rather than a complete fix via new clutch pack and internal components.

Thanks in advance,

Knox

 

[ixer0]

Hi,

Sounds like a broken buttress cap. You should be able to find a thread on here covering that problem

Mike

 

[knox]

Thanks. I'll inspect the buttress caps next chance (machine is 100mi away). But all 3 fingers were moving approx the same 1/16". Is it likely that all 3 caps would be broken at once?

while searching the treads about buttress caps I saw that 1/2" is the minimum slave piston movement. So perhaps I'd better concentrate on that area first.

 

[juney68]

Not sure if you have fixed this yet or not but I had a similar problem with ours. I had to drain the brake fluid and replace it with hydraulic fluid. It works fine now until it gets really cold(10F) and then it still works but is hard to push. I'm sure there are plenty of reasons I should not have done that, but I was in the same boat and did not want to tear it in two to replace the clutch as it is lightly used as well. It may help , don't know.

 

[ricc]

to me 2 inches of pedal travel without any slave cylinder movement would suggest a master cylinder problem.

id do a new cylinder before pulling the clutch apart.

 

[knox]

Thanks for the replies.

Over Christmas holidays I visually inspected the buttress caps from the inspection port and as far as I can see they're all in one piece.

I agree that the intermittent performance and odd clutch travel points to the master cylinder. I'm planning to order a master cylinder and replace it sometime in the coming weeks... will update the thread then.

I guess thicker oil could mask the symptoms of bad seals in the master cylinder, but it's a relatively cheap part to replace so I might as well do it right.

 

[knox]

I installed the new clutch master cylinder yesterday and it's working much better, though gears still grind sometimes if don't I bring RPMs down to low idle when shifting.

I push the clutch pedal 1/2" and it visibly starts to actuate the slave piston; fully depressed the slave piston now moves about 9/16".

If another novice like me is considering replacing the clutch master cylinder.... this may not be the best way to do the job, but this is what worked for me:

1. access through firewall panel between cab and engine (remove 5 bolts); my engine hood was already off due to engine work; open clutch inspection hatch to left of clutch pedal on cab floor; set 5 gal pail to catch brake fluid
2. spray all master cyl bolts with WD40 and crack loose both hydraulic lines 17mm (then snug them up to avoid fluid loss) before unfastening the master cylinder bolts.
3. move wiper fluid pump to get wrenching room
4. remove both master cyl mounting bolts 13mm
5. disconnect line from reservoir; I taped it up to keep dirt out and put it higher then reservoir to minimize fluid loss; topped up reservoir at this point
6. turn master cyl to remove line to slave cyl
7. install line from slave cyl to new master cyl (torque it)
8. mount master cyl using two 13mm bolts
9. reattach line from reservoir (torque it)
10. top up reservoir again for what fluid was lost in step 9 (I lost about half a reservoir both connecting and disconnecting; don't know if it's advisable to pinch the line on a 30 year old machine before disconnecting it).
11. pump pedal and bleed the slave 9mm deep socket with long extension on a T handle so I could pump pedal with one hand and turn bleed screw with the other.
12. reattach the wiper pump

Thanks all for the tips; all's well that ends well.