Bobcat 763 aux hydro issue

[Todd v.]

So I've had this machine for 8 years or so and it's always had this issue, when I put the aux hydraulics under load and try to tilt the bucket up it tilts down. When they aux hydraulics aren't under a real load everything works fine, like when the brush cutter is already up to speed. It does the same thing when I have the grapple bucket on. Also, it's not like it's in the easy release of hydraulic pressure mode to slowly bleed the bucket down, it's actually sending hydraulic pressure to tilt the bucket down when I try to tilt it up. But like said this only happens when the aux hydraulics are under a moderate load, as soon as the load lessens it works normally. The boom moves up and down normally while this is happening.

I never worried much about it and just avoided tilting the bucket when grabbing stuff but it's not so easy when running the brush cutter and it's trying to come back up to speed. I also seem to be loosing some aux hydro power after the machine is well warmed up and has been worked fairly hard for an hour or so and I'm thinking the two problems may be related, the gear pump only has about 300 hours on it. I'm thinking fluid is bypassing somewhere in the controls but have no idea where to look or how to diagnose it. I'm an auto mechanic not a hydraulics guy. Any help would be greatly appreciated.

 

[willie59]

Is it a C, F, or G series machine?

 

[Todd v.]

Is it a C, F, or G series machine?

I can't remember but I think it's a G. I left the machine on a job and won't be back there till Tuesday, can I tell from the serial number? It's a 99 & not a high flow.

 

[Todd v.]

I just found an old receipt that says it's an F series.

 

[willie59]

C and F series had rectangle shaped headlights.

C series has a two piece rear door, orange at the bottom with a black piece at the top.

F series has a one piece stamped steel rear door, all orange

 

[willie59]

When you say it only does this when you operate the aux hydraulics, does it have the same effect when you operate the aux in both directions?

 

[Desertwheeler]

C and F series had rectangle shaped headlights.

C series has a two piece rear door, orange at the bottom with a black piece at the top.

F series has a one piece stamped steel rear door, all orange

Unless my f had a different door put on it, mine was a 2 piece it was a 98 model.

 

[willie59]

Unless my f had a different door put on it, mine was a 2 piece it was a 98 model.

I can't answer that with any certainty, but to my knowledge, the F series had the one piece stamped steel door, but I have no way to say that's gospel. :beatsme

 

[Todd v.]

It does have the rectangular headlights and a one piece door. I will have to confirm if it does it in both directions though because I'm not sure. I'll report back tomorrow night.

 

[apetad]

It does have the rectangular headlights and a one piece door. I will have to confirm if it does it in both directions though because I'm not sure. I'll report back tomorrow night.

It doesn't matter which series. They all do that. It is normal while operating the auxiliary for loader lift & tilt to not function correctly

 

[Todd v.]

Ahh ok. I noticed today that it does it in both directions and it tries to dump the bucket and raise the lift arm but only when the valve for either is opened. Kinda crappy and makes it hard to do things smoothly while running the aux hydraulics.