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I have a 642b Bobcat and this last weekend i blew the

Customer Question
hydraulic line to the left...
i have a 642b Bobcat and this last weekend i blew the hydraulic line to the left side lift arm. I replace that and now the arms will raise but will not go down until i shut it off then it will. Also the bucket tilt would work as it is full extended and would come back up. At the time i had blew the line the auxiliary was on as i was using a post hole digger. I think the Auxiliary is stuck on. Is this causing the loader issue and if so how do I get the auxiliary off. Thanks
Submitted: 2 years ago.Category: Construction and Road Equipment
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Answered in 45 minutes by:
6/2/2020
Mechanic: Fieldtech59, Shop manager replied 2 years ago
Fieldtech59
Fieldtech59, Shop manager
Category: Construction and Road Equipment
Satisfied Customers: 201
Experience: Construction equipment repair technician since 1986, JLG certified, Shop manager since 2006.
Verified

Greetings, I can sort of answer your question, that is, yes, from what you're describing, that's typically cause by the auxiliary circuit is activated. What I mean by "sort of" is I've worked on piles of Bobcat machines but I've never worked on a 642B, I've worked on the 743B, but man, that vintage machine, that was years ago. I'm trying to recall how the 743B worked, and I could be wrong, but seems I recall you pushed the right drive lever outward to engage the auxiliary hydraulics, and then maybe use a thumb switch to control direction. Is that the way your machine works?

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Customer reply replied 2 years ago
The right handevel engages and disengage the auxiliary when you move it sided to side.
Mechanic: Fieldtech59, Shop manager replied 2 years ago

Yeah, I was just reviewing my manual on the 743B that I haven't looked at or worked on for years and oh man, Bobcat made crappy manuals back then. LoL. But it seems to show the same, move the right drive lever side to side to work auxiliary hydraulics. If that's the case my question would be does your right drive lever feel like it's actually moving the auxiliary hydraulic spool of the main control valve with snappy detent catches when you move the drive lever side to side? Or does the drive lever just feel loose and sloppy when you move it side to side?

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Customer reply replied 2 years ago
The drive lever feels loose and sloppy. When I have the cab up and look at the lever and were it attaches to the spool it does look like the spool is moving at all and that the spool is all the way in. I have tried to move the spool out but no luck with that.
Mechanic: Fieldtech59, Shop manager replied 2 years ago
I think that spool has detent balls to hold it engaged. Is the linkage that connects the drive lever to the spool good?
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Customer reply replied 2 years ago
The linkage looks good that connects to the drive lever.
Mechanic: Fieldtech59, Shop manager replied 2 years ago
I'm at work on lunch break, I'll see if I can come up with some info this evening. Could you provide the machine serial number
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Customer reply replied 2 years ago
Serial number is *****
Mechanic: Fieldtech59, Shop manager replied 2 years ago

Just what I suspected, there's two spools the main control valve that have a detent mechanism on them, one would be the lift spool, which is bucket float, shove the lift pedal all the way forward and it locks the spool in float position until you kick the pedal out of the detent. The other would be for the aux controls. Seems I recall on the 743B, you move the right drive lever to the left and right to control double acting aux circuit, but if you shove it far to the right it locks the aux spool with the detent for using attachments with motors, such as a brush cutter. I'd be willing to bet your detent mechanism on the aux spool is got the spool stuck in that position. I've attached a diagram that shows your main control valve, items #37 and #42 are the detent mechanism, items #38 and #39 are the springs and balls inside the mechanism.

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Customer reply replied 2 years ago
to get the aux spool unstuck do I need to take the main control value out or is there some way to get it unstuck with out going to all that work?
Mechanic: Fieldtech59, Shop manager replied 2 years ago

Well, that's a million dollar question. Again, I haven't worked on a 42 or 43 series machine for years. I do recall the first time I worked on a 743 back in the 90's, spool seals leaking on main control valve. I went to pull the lift function spool and yanked apart the detent mechanism, the spring and balls flew into oblivion in the belly of the machine. Learned a lesson that day. Most likely, from my experience with Bobcats, you've got some moisture inside the cap that encloses the centering spring and detent mechanism for the auxiliary spool, not uncommon on those valves, and now that moisture has caused corrosion that has the detent stuck. In that case, the first thing you should try is removing the cap that encloses the centering spring and detent mechanism for the aux spool, item #35. There's two allen head screws, #26, that mount that cap to the valve body. But before you remove the cap after removing those screws you have to remove snap ring #33 and washer #34. Once all that is removed see if the cap will slide off of the rear components of the spool. If it does, spray plenty of lube on the spool components and hope it penetrates to do the trick and re-install the cap and hope you can get things shook loose. If not, you're going to be pulling that spool, and if you do that you might as well pull all of them to replace spool seals on a machine of that vintage. Let me know what you find.

On second thought, item #33 is most likely an E clip, not a snap ring.

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Customer reply replied 2 years ago
Thanks I will give that a try later today. Thanks
Mechanic: Fieldtech59, Shop manager replied 2 years ago
Let me know what you find
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Customer reply replied 2 years ago
I removed both #26 allen screws and then took the linkage that is connected to it and rotated it as much as i could right and left. Hooked it back up and pull the lever outward to disengage and it disengaged. Everything works as it should . Thanks
Mechanic: Fieldtech59, Shop manager replied 2 years ago

Good news to hear you got it working again. Cheers!

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Mechanic: Fieldtech59, Shop manager replied 2 years ago

If it continues to happen, might try removing those two screws and see if you can get some separation between the cap and valve body and shoot some lube in there. Otherwise, it's take it apart.

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Fieldtech59, Shop manager
Category: Construction and Road Equipment
Satisfied Customers: 201
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Experience: Construction equipment repair technician since 1986, JLG certified, Shop manager since 2006.

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