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Bobcat t250 low charge pressure

joec2127

Member
Joined
Jul 10, 2009
Messages
7
Location
Jasper,GA
I have a 2005 Bobcat t250 2800 hrs foot control. I am getting a low charge pressure code followed by shut down. This happens after the fluid is up to operating temperature. When the code is thrown it feels like the brakes are engaging on both sides. Then the machine will shut down. I have checked the drive belt and it seems to be tight. Possible charge pump? Any feedback would be appreciated. Thanks
 

lantraxco

Senior Member
Joined
Jan 1, 2009
Messages
7,704
Location
Elsewhen
Possible, more likely bad drive pump or motor. As the fluid warms up it get's thinner and leaks internally more, and it gets to the point the charge pump is no longer supplying enough oil to keep up with all the leaks and the charge relief is actually fully closed and not having to dump any oil to keep the charge pressure from getting too high. Since the brakes are no doubt spring applied, same deal as the pressure drops the springs begin to over come the low oil pressure and drag or lockup ensues. In some drive pumps (I'm speaking generically about hydrostats, I am not familiar with the T250 in particular) the swash plates are shifted by servo cylinders using charge pressure, so when it gets too low the servos don't have enough push to stroke the pumps completely either.
 

joec2127

Member
Joined
Jul 10, 2009
Messages
7
Location
Jasper,GA
I would think if it was a bad drive motor I would see loss of fluid somewhere but I’m not. It has been running fine and then all of the sudden started doing this after I replaced the lift tilt valve and sylenoid.
 

lantraxco

Senior Member
Joined
Jan 1, 2009
Messages
7,704
Location
Elsewhen
It may be a possibility something you affected in your work has changed things. Drive pumps and motors can bypass internally, the oil dumps inside the case and flows to the cooler.
 

joec2127

Member
Joined
Jul 10, 2009
Messages
7
Location
Jasper,GA
That seems to be the issue. I changed the hydraulic filter and strained it and there were no shavings. I’m just trying to narrow this down before I tear into it.
 

joec2127

Member
Joined
Jul 10, 2009
Messages
7
Location
Jasper,GA
Ok so I finally got my machine to a mechanic and he is saying the whole hydraulic system will need gone through rather than replacing just the part with the problem due to contamination of metal that has probably damaged other components. Is there not something on these machines that prevent that from happening when a drive motor or pump goes out? I just don’t want to spend money that is unnecessary.
 

lantraxco

Senior Member
Joined
Jan 1, 2009
Messages
7,704
Location
Elsewhen
Ok so I finally got my machine to a mechanic and he is saying the whole hydraulic system will need gone through rather than replacing just the part with the problem due to contamination of metal that has probably damaged other components. Is there not something on these machines that prevent that from happening when a drive motor or pump goes out? I just don’t want to spend money that is unnecessary.
NOPE! That would increase cost to manufacture, and reduce parts sales long term. There are indeed bidrirectional high pressure hydraulic filters, but I have NEVER seen them used in any production machine. Only industrial systems typically.
 

Mbar

Senior Member
Joined
Dec 15, 2018
Messages
263
Location
North Carolina
I helped out the bobcat dealer here locally when they were short handed. I asked the same question of better filtration or filter cart after there was a failure, not much in response thought. I did rig up a filter housing and plugged it into aux ports. When repair is complete with new filters. Start machine and kick on aux and pull the trigger. Run for a little bit and change the filter. Do it again and add bucket movement and inspect filter. Keep doing this and work up to driving along with changing machine filters. It’s timely and seems expensive but better than full replacement.
 
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