Hello guys I hope all are dealing with new year and winter well. Linkbelt 4300c excavator when swinging clockwise or counterclockwise swingbrake will come on hard. If I barely move lever to swing left it will rotate 100 times if moved to right just lightly it will rotate 100 times. If I swing at a normal rate, it will swing maybe 1 or two revolutions then brake comes on either direction. I put my gauges on at my swing brake to check relief and dropped down the house pin to stop rotation and it relieves at 3000psi each direction. When I watch gauges with house pin out , pressure will increase until brake comes on . When I barely touch swing lever and begin to swing pressure will start to rise then drop off and continue to rotate as many times as I want to until I give it more lever then pressure will rise until brake comes on and stops rotating. Pulled valves off at brake hoping to find something out of ordinary but all looked fine . Next I will look at control valve to see if spool spring is broke. Any ideas ?
Is the slewing gear box making oil. If you dead the swing brake line disconnected with a plug / gauge in it does it do the same thing? you can also use a porta power with a ball valve and a gauge connected to the swing break and pump it up to the relief pressure and close off the valve and see if the brake will hold pressure?
This swing unit does not use friction discs. Also swing motor does not have fluid coming out case drain when operating which is good
10-4 Does it use cross over for braking?
Yes I pulled each valve out looking for damage but nothing out of ordinary,no debris
I'm not sure on your particular swing motor but some had a shuttle valve spool built into the counter-balance valve housing. Do you know if yours has that?.
Sorry about the late response bad freezing at work. I will search my hydraulic schematics when I get home if it is something directly in the swing brake valve I may not know what I am looking at I know that from my mcv the piping goes straight to swing brake valve
It has a flat plate under the brake valve which 3 hoses go to , but I believe those are for the brake holding switch when digging on a slope. I had a hyd schematic on a past post. I will try to post that again
Sorry about the poor photos I will get a better schematic soon . It looks as though the shuttle valve is before the mcv and not directly on the swing brake valve . Trying to identify could be a Block it looks as though the pilot lines connect to manifolds before mcv. Serial c1h7-0654. 43ouf-5228