bobcat 331 excavator swing brake

[Nelty]

Hi everyone, Nelty here and I have a 331 excavator that the swing brake does not hold in place when you release the joy stick. It stops as should when swinging just does not hold it when digging. I see there are two relief valves and two plungers with springs under the relief valves. Is this what holds the machine from swinging and how do you check to see witch one is bad or am I way out in left field? S/N 511920070 thanks for any info in advance. Nelty

 

[SSdoxie]

The relief valves and springs are Cross Port Reliefs, yes this is what stops the motor when joystick is returned to neutral. There is no absolute brake on the motor thus anytime a heavy side load on the bucket forces internal pressure in the swing motor to exceed the relief setting the motor will move. To test relief use the transport lock to pin the house from swinging Check the valve assembly that controls swing if there is a test port installed you can attach 5000 psi gauge there, if no test port tee gauge into each of the work port hoses to the motor then start machine and move joystick to stall the motor with house locked in place.

 

[Nelty]

Thank you very much SSdoxie, what should the relief pressure be set at, I can push the house around by hand just by leaning against it. Thanks in advance, Nelty

 

[laurencen]

if locked does it attempt to pressure up when the joystick is moved, my guess is the relief valve is stuck, how many hours on machine

 

[Nelty]

laurencen, thanks for the info trying to change the hydraulic hoses from the boom to valves rite now, may be a while before I get back to the swing brake. 25 year old hoses are pretty brittle and machine set for about four years didn't help any. Will get back with you after changing hoses, Thanks again for every ones help, good to know you can still get good help out there in this mixed up world. talk to you all later. Nelty

 

[SSdoxie]

The cross port reliefs for that motor come preset @ 2100 psi.

 

[Nelty]

Hi everybody I'm back hoses are changed and ready for more fun. I did check the swing with it locked at a idle and it did pull the motor down a good bit but didn't stall it. When you swing it unlocked and let go of the joy stick it will stop fast enough to slide the tracks a little, but you can still push the house around. Any ideas greatly appreciated, Thanks in advance, Nelty

 

[SSdoxie]

Hi everybody I'm back hoses are changed and ready for more fun. I did check the swing with it locked at a idle and it did pull the motor down a good bit but didn't stall it. When you swing it unlocked and let go of the joy stick it will stop fast enough to slide the tracks a little, but you can still push the house around. Any ideas greatly appreciated, Thanks in advance, Nelty

Stopping fast enough to slide tracks, cross port reliefs are working as designed. Motor has a case drain circuit for internal cooling, a designed percentage of oil will pass through case drain when side load pressure is applied to the bucket. The farther out bucket is from the house the easier it is to force oil out the case drain. When digging, trying to shave side of a hole it is normal for this to drift. Hold slight pressure on the swing joystick to over come the case drain flow to keep the bucket where desired.

 

[Nelty]

Thanks everyone for your expert support , the books I have show all the part numbers and parts but doesn't tell me anything about how it works or how to fix it. I guess i'm good to go then, this is a great forum so thanks again everybody for the help it is greatly appreciated. Till the next time, Nelty

 

[laurencen]

for what its worth both my E32 and 430 with the arm extended fully its impossible for me to rotate the house, you have something bypassing somewhere maybe a piece of rubber in the valve or relief