blew another gear pump

[jds]

So about 5 months ago i lost lift and tilt and found that the gear pump was bad. I replaced the pump with a new one and all was well, my lift and tilt came back and worked great....until now. Now i have the same issues and lost another pump. I have another one coming but need to find out what is going on so i dont blow another pump. loader parts source looked at it and said it was lack of oil. Im not sure how this would be possible because the supply hose goes directly to pump from resevoir and has a steel spring inside so its not like its collapsing under pressure. Also the resevoir was never low on oil. filters are up to date. this is a 2000 773 bobcat. Any ideas on why im losing my gear pump would be greatly appreciated!

 

[jerry]

Have you had the suction hose off and ran a wire or air through it to make sure there is nothing in there? People have found rags , plugs and other things in those hoses.

 

[jds]

Have you had the suction hose off and ran a wire or air through it to make sure there is nothing in there? People have found rags , plugs and other things in those hoses.

Thanks for the response...yes i did take suction line off and cleaned it up. no obstruction in the line though

 

[antfarmer2]

Thanks for the response...yes i did take suction line off and cleaned it up. no obstruction in the line though

Are you using the right oil?

 

[jerry]

Are you using the right oil?

Has it been really cold there? I have no idea unless the filter froze but I think bobcats filter return oil so thats out.

 

[samsonite]

Has it been really cold there? I have no idea unless the filter froze but I think bobcats filter return oil so thats out.

My money is on the replacement gear pump being a dud. Hard to starve that pump if the fluid levels are correct and the oil is clean and flowing.

 

[TriHonu]

My money is on the replacement gear pump being a dud. Hard to starve that pump if the fluid levels are correct and the oil is clean and flowing.

Check the Breather Cap on the hydraulic reservoir. If it is plugged you can starve the pumps.
Bobcat Maintenance Schedule lists it for replacement every 500 hours (or as required).

 

[jerry]

Check the Breather Cap on the hydraulic reservoir. If it is plugged you can starve the pumps.
Bobcat Maintenance Schedule lists it for replacement every 500 hours (or as required).

That may be it, you have to have air going in for oil to go out and I think that is the most neglected filter on there. I had one that came from a farm that was almost solid black dirt. Lots of air moves through there when ever you use a cylinder.

 

[TriHonu]

That may be it, you have to have air going in for oil to go out and I think that is the most neglected filter on there. I had one that came from a farm that was almost solid black dirt. Lots of air moves through there when ever you use a cylinder.

Yep, easy to forget that it takes a lot more oil to extend a cylinder than what comes back to the reservoir from the gland end, especially with the larger rod diameters. It's worse with with long stroke cylinders. That breather is required or you will create a vacuum in the reservoir.
The drive motors aren't an issue since what goes out just cycles through the motor and back to tank.
Not the only cause for lack of oil, could also be a fitting on the suction line that is not sealed and it's sucking air.

 

[samsonite]

Yep, easy to forget that it takes a lot more oil to extend a cylinder than what comes back to the reservoir from the gland end, especially with the larger rod diameters. It's worse with with long stroke cylinders. That breather is required or you will create a vacuum in the reservoir.
The drive motors aren't an issue since what goes out just cycles through the motor and back to tank.
Not the only cause for lack of oil, could also be a fitting on the suction line that is not sealed and it's sucking air.

Case drains should be change as well. Leave nothing to chance with a pump failure.