773 F SERIES BOBCAT

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I AM TRYING TO GET SOME TESTING INFO ON MY 773 F SERIES BOBCAT TO SEE IF THE HYDRAULIC PUMP OR THE MAIN RELIEF VALVE HAS FAILED I TESTED THE PRESSURE AT THE AUX HYDRO PORT AND ONLY GOT 1200 PSI I SHOULD HAVE 3000 SO SHORT OF PULLING THE ENGINE ASSY TO GET TO THE PUMP I AM LOOKING FOR ANYONE ELESE THAT HAS DELT WITH THIS SITUATION THE BOOM AND BUCKET WILL ONLY MOVE WHEN THE ENGINE IS RUNNING AT FULL THROTTLE AND THEY MOVE SLOWLY AT BEST WITH LITTLE POWER ANY HELP IS GREATLY APPRECIATED THANKS GENE
 

Tazza

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First of all:
capslock.jpg

The only way to know for sure is to get the pump tested. They fit a flow meter and pressure gauge to the main oil line and increase the pressure and measure flow. If the flow drops right off, the pump is bad.
I don't know that you have to pull the engine/pump to get to the hydraulic pump. I thought there was just enough room to get it out while still in place.
Has the pressure slowly dropped or is it more of a sudden thing?
If you remove the relief from the control block, you can check the spring isn't broken and nothing is stuck in it to cause low pressure.
 

OldMachinist

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Hey Gene,
Do you have a manual for your machine?
http://www.bobcatstore.com/category.html;jsessionid=0a06662030d8c6b21f27de8343469b4c8d592206b6a3.e3qPbheMc38Ke3qOc3aQch4Mbi0.2?categoryId=1460
Tazza,
Love the caps lock message!! I will have to remember that one.
Cheers,
SR
The first thing to check is the pump drive belt tension. If the belt is loose you will have low pressure. It's behind the plastic cover on the left side of the engine.
DriveBeltCover.jpg
 
OP
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G
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The first thing to check is the pump drive belt tension. If the belt is loose you will have low pressure. It's behind the plastic cover on the left side of the engine.
i did check the belt the tensoner and the belt at about 1 year old the unit lost power in the matter of 1 day but it drives just fine it has plenty of drive power just no power to the boom and bucket i am getting a meter assy that will allow me to put back pressure on the pump it self i will connect the line to the pump and i can restrict the flow i don't have to go all the way to 3000 psi but as long as i can get more than 2500 i can safely rule out the pump then i will reinspect the main relief valve it is not serviceable i cant look inside of it but i may just replace it this unit has 8892 hr it was deliver to us 1998 and has been in almost Constance use at least 5 days a week we use it for everything i will email to get a manual if i dont have to take out that pump that would be nice Thank you for your input
 

Tazza

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i did check the belt the tensoner and the belt at about 1 year old the unit lost power in the matter of 1 day but it drives just fine it has plenty of drive power just no power to the boom and bucket i am getting a meter assy that will allow me to put back pressure on the pump it self i will connect the line to the pump and i can restrict the flow i don't have to go all the way to 3000 psi but as long as i can get more than 2500 i can safely rule out the pump then i will reinspect the main relief valve it is not serviceable i cant look inside of it but i may just replace it this unit has 8892 hr it was deliver to us 1998 and has been in almost Constance use at least 5 days a week we use it for everything i will email to get a manual if i dont have to take out that pump that would be nice Thank you for your input
Almost 9,000 hours Wow, that machine is doing really well. Is it still on it's first engine?
For the pressure to drop off so fast, it's hard to condem the pump so easily. Your plan on restricting the the pump and read the pressure is a good one. it will tell you if the pump is at fault or not.
SkidRoe - I found it on the net yesterday, i think i'll start using it more often too :)
 
OP
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G
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Almost 9,000 hours Wow, that machine is doing really well. Is it still on it's first engine?
For the pressure to drop off so fast, it's hard to condem the pump so easily. Your plan on restricting the the pump and read the pressure is a good one. it will tell you if the pump is at fault or not.
SkidRoe - I found it on the net yesterday, i think i'll start using it more often too :)
yes it is still the first engine it has been serviced with only Mobil 1 full synthetic oil and only oem filters however it is starting to show its age due to its high usage it is serviced every 2 weeks apx 50 to 70 hr's i am getting the meter this morning and will post the results soon Thanks
 
OP
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G
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Almost 9,000 hours Wow, that machine is doing really well. Is it still on it's first engine?
For the pressure to drop off so fast, it's hard to condem the pump so easily. Your plan on restricting the the pump and read the pressure is a good one. it will tell you if the pump is at fault or not.
SkidRoe - I found it on the net yesterday, i think i'll start using it more often too :)
ok the votes are in the pump has been officaly declared the looser the pump will only produce 1200 psi so now the process begins such fun
 

Tazza

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ok the votes are in the pump has been officaly declared the looser the pump will only produce 1200 psi so now the process begins such fun
Still, that is some pretty good life from a pump of that many hours of service.
Do let us know how the swap goes. I was under the impression it could be done in the machine, but i bet access is not fun....
 

OldMachinist

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Still, that is some pretty good life from a pump of that many hours of service.
Do let us know how the swap goes. I was under the impression it could be done in the machine, but i bet access is not fun....
It's not too bad of a job to remove the pump. On the early model the the tilt lock valve needs to come out. Other than that its draining the hydraulic system, removing a few hoses and using a modified 5/16" hex key wrench. You have to shorten the short leg of the wrench to clear a fitting.
 

7LBSSMALLIE

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It's not too bad of a job to remove the pump. On the early model the the tilt lock valve needs to come out. Other than that its draining the hydraulic system, removing a few hoses and using a modified 5/16" hex key wrench. You have to shorten the short leg of the wrench to clear a fitting.
another trick is to cut a piece off the 5/16 allen or 8 mm and use gear wrench
 
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G
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and by the way lose the allen heads put back standerd 3/8 hard ware if you can;
i will tear down the pump when it is removed so i can do a failure analysis if the pump ejected any metal i have more problems down stream that will have to be delt with quickly to prevent more problems how do you post pictures on this site
 
OP
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G
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Hi Gene,
Check this link out:
http://www.skidsteerforum.com/DesktopDefault.aspx?tabid=54&frmView=ShowPost&PostID=2445
HTH,
SR
when the pump was torn down i found the problem it was a o-ring that probably cost 4 cents to make it seperates the high and low pressure ports on the pump i could replace the o-ring but the pump has wear and the pressure would be good but not perfect it took 3.5 hr to replace the pump bobcat says that is the proper time i will installe a new o-ring and use the pump for some other project and now the boom moves at the proper speed at idle
gotta love it


image.jpeg
 

skidsteer.ca

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when the pump was torn down i found the problem it was a o-ring that probably cost 4 cents to make it seperates the high and low pressure ports on the pump i could replace the o-ring but the pump has wear and the pressure would be good but not perfect it took 3.5 hr to replace the pump bobcat says that is the proper time i will installe a new o-ring and use the pump for some other project and now the boom moves at the proper speed at idle
gotta love it
Lol @ Tazza
Gotta save that pic!
 
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