751- c groan

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FFPK751

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Oct 5, 2005
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Question regarding the 751. I have a 95 751 with the Peugot motor. It has a little over 2000 hours. I have not put too many hours on this machine yet, but one thing I have noticed is that unless the RPM's are up (more than 1/2 throttle) the machine really groans unless going perfectly straight. Is this normal? Thanks FFPK
 

Eric

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Jan 19, 2005
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It soumds like that is normal for half throttle. I usualy run my machines at least 3/4 throttle and full throttle when Im being realy demanding on the machine. You have to remember, everything on these skidsteers are ran from hydraulics. The higher rpms the engine runs at the more smoothly it can handle the demands of the hydraulic system when using all your machines functions.
 

Tazza

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It soumds like that is normal for half throttle. I usualy run my machines at least 3/4 throttle and full throttle when Im being realy demanding on the machine. You have to remember, everything on these skidsteers are ran from hydraulics. The higher rpms the engine runs at the more smoothly it can handle the demands of the hydraulic system when using all your machines functions.
That is totally normal, they are made to run at full or almost full throttle. If its not high enough the hydrostatic pump will groan and the hydraulic pumps vanes will not fully extend causing it to cavetate and cause pump damage (this is at very low speed like idle). It is normal for it to still groan a small amount at full throttle under high load, especially when its still cold. But if it still squeels and groans loudly even at high RPM you may have a filter blockage.
 

FFPK751

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That is totally normal, they are made to run at full or almost full throttle. If its not high enough the hydrostatic pump will groan and the hydraulic pumps vanes will not fully extend causing it to cavetate and cause pump damage (this is at very low speed like idle). It is normal for it to still groan a small amount at full throttle under high load, especially when its still cold. But if it still squeels and groans loudly even at high RPM you may have a filter blockage.
Thanks for the info. It is greatly appreciated. Is there any way to monitor or check the filters without replacing? Phil
 

Tazza

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Thanks for the info. It is greatly appreciated. Is there any way to monitor or check the filters without replacing? Phil
There may be pressure switches in the filter housing that will sense when the pressure is higher than normal due to filter blockage but i am not sure if the 751's have this. Filters are cheap insurence, just change it. There may also be a bronze filter on an inlet line to the hydrostatic pump that may be blocked. Call your locak Bobcat dealer and talk to the service department to find where the filter is located and replace it. You can clean them, but honestly, for the price buy a new one they aren't too easy to clean.
As you don't know what the previous owner has done to the machine i would advise you change the hydraulic oil filter, the engine oil and filter also the fuel filter. Write the date and hour meter reading on them so you know where you are at. Keep the maintenance up to it and it should serve you well.
I hope this is of some help.
Don't be afraid to call your Bobcat service department, they are VERY helpfull, tell them the problem and they will try to help you out.
 

bobbie-g

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There may be pressure switches in the filter housing that will sense when the pressure is higher than normal due to filter blockage but i am not sure if the 751's have this. Filters are cheap insurence, just change it. There may also be a bronze filter on an inlet line to the hydrostatic pump that may be blocked. Call your locak Bobcat dealer and talk to the service department to find where the filter is located and replace it. You can clean them, but honestly, for the price buy a new one they aren't too easy to clean.
As you don't know what the previous owner has done to the machine i would advise you change the hydraulic oil filter, the engine oil and filter also the fuel filter. Write the date and hour meter reading on them so you know where you are at. Keep the maintenance up to it and it should serve you well.
I hope this is of some help.
Don't be afraid to call your Bobcat service department, they are VERY helpfull, tell them the problem and they will try to help you out.
I believe Tazza is correct about the lamp indicating filter blockage, although it is noted as a "transmission warning light." The operator's manual says " Low transmission charge pressure, hydraulic filter needs replacement, or high fluid temperature. Stop the eignie if the light comes "ON"." Hydraulic/hydrostatic filter replacement interval is listed as 250hrs. The bronze filter(s) Tazza is referring to are actually a pair, located in return (low pressure) lines. They are inside aluminium housings. Cab must be tilted backwards to access them. (And with no bucket, the arms raised/supported by an 8' 4x4 for safety and the cab raised, the 751C is very close to tipping over backwards, put some jackstands under the housing under the engine, I very nearly dumped mine over backwards). One filter is located just under the hydrostatic reservoir in a shiny housing about 1.5 inches in diameter and 3 inches long. The other is a bit harder to find, being buried down low near the left two drive shaft housings. Remove the exterior plate between the two left wheels for access, but expect to do a lot of reaching and stretching to remove and replace it. I believe both have o-rings at either end, so are not too tight, fortunately, because the wrench ain't made what will easily fit down in there and still turn. Having said all that, I replaced the bronze elements ($20 each for the elements, $30 each if you buy the element/housing combo) at 1100 hrs and found only a little bit of visible debris, but who knows how much invisible stuff they had collected. I'm guessing they are what's referred to as "case drain filters" in the Operation and Maintenance manual, and the listed change interval is 1000 hrs. If you try this, it's not too difficult, but you should replace all the hydrostatic fluid at the same time (also 1000 hr interval), since it's much easier to work with the filters if the tank is empty. Then you know you have clean fluid until you rent your next tool, then you're back to polluted again.... :) Bob
 

Tazza

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I believe Tazza is correct about the lamp indicating filter blockage, although it is noted as a "transmission warning light." The operator's manual says " Low transmission charge pressure, hydraulic filter needs replacement, or high fluid temperature. Stop the eignie if the light comes "ON"." Hydraulic/hydrostatic filter replacement interval is listed as 250hrs. The bronze filter(s) Tazza is referring to are actually a pair, located in return (low pressure) lines. They are inside aluminium housings. Cab must be tilted backwards to access them. (And with no bucket, the arms raised/supported by an 8' 4x4 for safety and the cab raised, the 751C is very close to tipping over backwards, put some jackstands under the housing under the engine, I very nearly dumped mine over backwards). One filter is located just under the hydrostatic reservoir in a shiny housing about 1.5 inches in diameter and 3 inches long. The other is a bit harder to find, being buried down low near the left two drive shaft housings. Remove the exterior plate between the two left wheels for access, but expect to do a lot of reaching and stretching to remove and replace it. I believe both have o-rings at either end, so are not too tight, fortunately, because the wrench ain't made what will easily fit down in there and still turn. Having said all that, I replaced the bronze elements ($20 each for the elements, $30 each if you buy the element/housing combo) at 1100 hrs and found only a little bit of visible debris, but who knows how much invisible stuff they had collected. I'm guessing they are what's referred to as "case drain filters" in the Operation and Maintenance manual, and the listed change interval is 1000 hrs. If you try this, it's not too difficult, but you should replace all the hydrostatic fluid at the same time (also 1000 hr interval), since it's much easier to work with the filters if the tank is empty. Then you know you have clean fluid until you rent your next tool, then you're back to polluted again.... :) Bob
See, some people know what they are talking about :)
I totally agree with bobbie, drain the hydraulic/hydrostatic fluid, replace the filters then you are rite for 1000 hours on the oil and case drain filters. Just replace the other filter regularly. Replacing filters with full hydraulic lines is good fun, you quickly run out of fingers to plug the lines! this is where helpers come in very handy.
Ahh yes, you rent an attachment and you can get any old oil in your system....
 

FFPK751

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Oct 5, 2005
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See, some people know what they are talking about :)
I totally agree with bobbie, drain the hydraulic/hydrostatic fluid, replace the filters then you are rite for 1000 hours on the oil and case drain filters. Just replace the other filter regularly. Replacing filters with full hydraulic lines is good fun, you quickly run out of fingers to plug the lines! this is where helpers come in very handy.
Ahh yes, you rent an attachment and you can get any old oil in your system....
You guys are great. Thank you. Phil
 
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