Poclain 75 CKB

[Jeremy Rowland]

Well it's been a while since I posted anything here; the main reason was that as Andrew's working event was getting close I did not want this machine out of action, and after the event I have spent much time cleaning both this machine and the Hymac, getting the mud from off them.

There is still the niggling issue of the two speed track problem with this digger; after much ado I have now got two contacts that can give me some help, one in the form of Generation Deux who are the French Poclain enthusiasts and a chap I got talking to at Andrew's event who used to work on Poclain machines. I was recommended by the chap I met at the working event to swap over the two track spools that are fitted to the outside of the track drive motors, and the gent from France advised me to strip the spool.

Now for me the big issue was that I really did not fancy draining off all the hydraulic oil again and as these components are at the very bottom of the machine, if I swapped them around then unless I had drained the oil there would have been a mess everywhere plus the added cost of new oil. I decided to strip down the suspect component in-situ now there would still be some oil loss. Part of the problem is that the piston/spool inside the unit has a couple of springs fitted behind it although the piston can be hard to remove because of oil suction.
The last thing I wanted was for all the bits to suddenly spring out and fly allover the place, so I made a tool to hold the cover in place while I removed the circlip holding the lot in.

Naturally sods law applies as always and after much of a struggle I finally got the circlip out, it was only then that I could fit my homemade tool, the next issue was that the plug covering the bits was seized in and there is no way to lever it out. Finally I fitted the tool and left only a small gap between the bolt and plug then started the digger and carefully operated the track drive pedal letting the hydraulic pressure free the plug and blow it out, the tool stopped the plug from flying right out. I removed the piston, took the plug out of it and checked the spool inside it, no problem there, removed the springs they too were okay, so a pretty fruitless exercise, at least I can rule that issue out now, so I put the lot back together again.

Jeremy

[essexpete]

Jeremy can you remind us of the exact symptoms and problem?

[Jeremy Rowland]

Jeremy can you remind us of the exact symptoms and problem?

The machine tracks fine in the fast speed tracking mode, just that apparently it isn't designed to steer very well in fast track mode, when you throw the switch in the cab to low track speed, only the right hand track operates. I am sure the engine note changes as if the machine is trying to do something but the left track will not rotate in the slow speed mode, even if you jack the machine up with the arm.

Jeremy

[essexpete]

Jeremy it is coming back to me now. I am no hydraulic expert but remind me of the number hydraulic connections to the final drive motor?
When in hi speed will the problem track drive under load in a similar way to the other one?
With care, is it possible to swap over the motor feeds from the rotary coupling? Just thinking that might eliminate a drive motor fault?

[Jeremy Rowland]

Jeremy it is coming back to me now. I am no hydraulic expert but remind me of the number hydraulic connections to the final drive motor?
When in hi speed will the problem track drive under load in a similar way to the other one?
With care, is it possible to swap over the motor feeds from the rotary coupling? Just thinking that might eliminate a drive motor fault?

I have been advised to do this Pete thanks, there are some other avenues that also need to be eliminated, those too are under investigation. Cheers.

Jeremy

[Jeremy Rowland]

Okay then; yippee, whoopee, thank goodness for that!

Left hand track problem solved at last, so I began checking hydraulic oil pressures for this machine; the high pressure was fine and despite doing bits and pieces and checking things with which there was no fault, I finally checked the low pressure feed to each of the two track motor spool feeds and found something very interesting. First off I confirmed that the fault was as I suspected a hydraulic one and not an electrical one or mechanical one, when I fitted the gauge to the good side (right hand track spool) the gauge read 13 bar which is correct, and this was only when the switch in the cab was activated, when not activated it read zero which was also correct.
When I tried to measure the pressure on the left hand track the gauge immediately jumped to 27 bar regardless of the switch position and without the track pedals being activated. The interesting thing was that the machine wanted to track in low speed on that side when the gauge was fitted, something it had not done since I purchased it.
After further contact with my friend in France he suggested that one of the low speed pipes was incorrectly connected to the rotary coupling, I checked exactly how this should be piped in the workshop manual (he had kindly supplied a pdf file of it for me) so today I crawled under the machine and physically followed the pipes on the left hand side; bingo got it! the two low pressure pipes were incorrectly fitted so I swapped them over. Now when I did the coupling a few months or so back I had marked the pipes with coloured cable ties to prevent this issue, but not realizing that in the past somebody else had already incorrectly fitted one. Job done so and it now works fine as it should, it is problems like this that are a challenge to find out exactly what the problem is. I marked the one pipe that was wrongly connected with two red cable ties in the last photo.

Jeremy

[Matchless?58]

Persistence pays off ! Well done Jeremy . Happy tracking mate .

[essexpete]

Sorted Jeremy!

[Jeremy Rowland]

Having completed the restoration of the 580BT control levers, my next task was also unplanned, while running up the Poclain during one of my visits, I discovered a cracked track link also she has developed an oil leak from somewhere underneath by the rotary coupling which I had replaced the seals on. This last Thursday I decided to make getting the track link repair completed, so after charging the one battery and topping up the hydraulic oil, I got her running.
The digger was reversed into Andrew's shed and I got assistance from Tony Wilson who cut the crack right out of the link and MIG welded it for me, so a big thanks to him.
While I had her up in the air, it was time for me to investigate the oil leak which turned out to be a simple fix, one of the rotary coupling connections was weeping, I managed to tighten it and it was a good job so a well spent day for me.

Jeremy

[Jeremy Rowland]

Last weekend I finally made my first trip up to my machines since before Christmas my last chance to get up there before had been scuppered by an outbreak of Covid in my office at work which got around 8 out of 10 of us.

The weather this year has been incredibly wet so I've saved my precious days off for better weather to get things done, I had a couple of objectives to carry out, one of which was to fit another new battery on the Poclain. I removed both batteries and cleaned out the compartment after which I fitted two cheap rubber car mats for the two batteries to sit on.

With the batteries fitted and the covers off I ran her up, she started first time my second objective was to get the machine washed off, it's nearly impossible to stop the greenery from growing on the paintwork, just for once the weather held out and I was able to get this done.

With that complete I opted to run up the 580BT so not a bad days work.

Jeremy