751 Froze up! Won't move, arms won't raise, bucket won't tilt.

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dfriend

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Jun 21, 2012
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I am sure this isn't the first post about this, but every search I tried returned no answers. Here's the issue: Bobcat 751 with rectangular headlights. The machine had a leak off the control block, after several hours of contorting, I finally got it sealed up and no more leak. It would start up, and as it was running, the pump had a grinding sound like it was loading up, but all functions worked. Neighbor borrowed the machine to do some light grading, and it broke down over at his house. I got the machine home, and started to look into the issue, but nothing was happening, no movement in the wheels and no motion in the arms or the bucket. Left the machine sitting for a month or so and went off doing other projects, and came back to it. For the first 30 seconds that I fired the machine up, the grinding sound in the pump was back, and I was able to tilt the bucket to where the teeth were off the ground, but no lift and no movement in the wheels. And then the grinding sound went away and no more tilt either. Hydraulic oil is half way up the dipstick. The lap bar light and the traction light both come on constant, but the other two lights the seat and the arms light blink twice. Is this electrical? Is no noise from the pump a sign that the pump is shot? Or what?? I am at a loss. If there are other posts about this, and hopefully about solutions, please point me in that direction. Thanks
 

melli

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Mar 25, 2012
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How can you hear pump over engine? If you can hear pump 'grinding' over engine, then I'd say you roasted your pump. Did you bleed pump (get air out)? Only time I could hear a hydraulic pump over engine was when I had air in mine. I quickly stopped and bled air out. Leak off control block? Through a hose fitting, or? When you say grinding, I think of a garburator in operation....is that what you were hearing?
 
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dfriend

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How can you hear pump over engine? If you can hear pump 'grinding' over engine, then I'd say you roasted your pump. Did you bleed pump (get air out)? Only time I could hear a hydraulic pump over engine was when I had air in mine. I quickly stopped and bled air out. Leak off control block? Through a hose fitting, or? When you say grinding, I think of a garburator in operation....is that what you were hearing?
Thanks for answering Melli- Yes, it was leaking off one of the fittings. It had been going on for quite a while when I finally got the fitting tight enough that it would stop. The only way I can describe the grinding noise would be like if you left the brake on, or didn't push the "push to operate button" and tried to roll forward, that kind of whining, grinding noise that it makes. I'm pretty sure the sound comes from the pump.....I really don't know how else to describe it. It is a distinct sound, that I have heard on many skidsteers over the years when operating, but I am not a mechanic, so I am explaining the best I can.
 
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dfriend

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Jun 21, 2012
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How can you hear pump over engine? If you can hear pump 'grinding' over engine, then I'd say you roasted your pump. Did you bleed pump (get air out)? Only time I could hear a hydraulic pump over engine was when I had air in mine. I quickly stopped and bled air out. Leak off control block? Through a hose fitting, or? When you say grinding, I think of a garburator in operation....is that what you were hearing?
Nothing at all? I came to this forum so confident that I would at least walk away with some sort of a direction.....and nothing? Come on guys, I REALLY need some help on this, I am completely vexed.
 

Tazza

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Nothing at all? I came to this forum so confident that I would at least walk away with some sort of a direction.....and nothing? Come on guys, I REALLY need some help on this, I am completely vexed.
Seriously? you post a question and expect it to be answered straight away. I for one have things to do on my weekends so i'm not here reading posts. Sadly you are not the first person to ask for help on here and complain when you don't get an answer within hours.......
The first thing i'd check is the drive belt, make sure the pump is still turning, if it is, you need to check that the shaft through the pump is turning to the hydraulic pump. For there to be nothing moving, it does sound like the pump or the connection between the pump and motor.
 
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dfriend

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Jun 21, 2012
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Seriously? you post a question and expect it to be answered straight away. I for one have things to do on my weekends so i'm not here reading posts. Sadly you are not the first person to ask for help on here and complain when you don't get an answer within hours.......
The first thing i'd check is the drive belt, make sure the pump is still turning, if it is, you need to check that the shaft through the pump is turning to the hydraulic pump. For there to be nothing moving, it does sound like the pump or the connection between the pump and motor.
OK, thanks for taking the time to answer, Tazza. I have watched you guys get very detailed and straighten a lot of us novices out with some incredible detail. I jumped the gun by hoping for some of the same help being sent my way. My bad.
 

gearbox

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Oct 24, 2013
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OK, thanks for taking the time to answer, Tazza. I have watched you guys get very detailed and straighten a lot of us novices out with some incredible detail. I jumped the gun by hoping for some of the same help being sent my way. My bad.
I am no expert on a 751 but is it possible that your 3 rd valve is engaged . I think you pull one of the levers toward you to engage . There is a lot of guys on here that will know what I am saying and will chime in .
 
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dfriend

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Jun 21, 2012
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I am no expert on a 751 but is it possible that your 3 rd valve is engaged . I think you pull one of the levers toward you to engage . There is a lot of guys on here that will know what I am saying and will chime in .
Gearbox! I think you might be talking about the aux valve. At one time I think the right operators handle had to be shifted left or right to engage it. I will certainly give that a try in the morning! Thanks for jogging my memory on that, and if that's the fix, somehow, I am buying you a beer! Thanks for answering my post.
 

Tazza

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I am no expert on a 751 but is it possible that your 3 rd valve is engaged . I think you pull one of the levers toward you to engage . There is a lot of guys on here that will know what I am saying and will chime in .
Having the aux (3rd valve) stuck on will make the lift/tilt work weird or not at all, but it should still drive.
 
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dfriend

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Jun 21, 2012
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Having the aux (3rd valve) stuck on will make the lift/tilt work weird or not at all, but it should still drive.
That makes sense. But I have NO seat light now and the tilt valve is blinking 2 times....so, now I go glue that sensor on the seat, like I read you suggested to Rodbuilder a while back....maybe heat up the safety valve, as suggested by another gentleman on the same post about the sensor and it preventing the BICS valve from opening, and then I look into if I have any flow through the pump....which I am pretty certain there is NONE....but I gotta start with the belt>Pulley>Shaft rotating first. I am making progress Tazza on suggestions and eliminations....thanks for the heads up on the aux v.
 
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dfriend

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Jun 21, 2012
Messages
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Seriously? you post a question and expect it to be answered straight away. I for one have things to do on my weekends so i'm not here reading posts. Sadly you are not the first person to ask for help on here and complain when you don't get an answer within hours.......
The first thing i'd check is the drive belt, make sure the pump is still turning, if it is, you need to check that the shaft through the pump is turning to the hydraulic pump. For there to be nothing moving, it does sound like the pump or the connection between the pump and motor.
Would there be any simple tell-tale signs that the shaft through the pump is turning to the hydraulic pump? Other then pop open a line behind the pump?
 
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dfriend

Member
Joined
Jun 21, 2012
Messages
18
Seriously? you post a question and expect it to be answered straight away. I for one have things to do on my weekends so i'm not here reading posts. Sadly you are not the first person to ask for help on here and complain when you don't get an answer within hours.......
The first thing i'd check is the drive belt, make sure the pump is still turning, if it is, you need to check that the shaft through the pump is turning to the hydraulic pump. For there to be nothing moving, it does sound like the pump or the connection between the pump and motor.
......the belt was loose. Adjusted the tensioner and fired it up, arms went up, bucket tilted and machine moved forward and back. Thanks for the recommendations Tazza
 

Tazza

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......the belt was loose. Adjusted the tensioner and fired it up, arms went up, bucket tilted and machine moved forward and back. Thanks for the recommendations Tazza
Good to hear it was an easy fix.
 

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