Swing circuit · High
Swing is slow, or will not hold a load
The house turns, but late and weak. Under a load it creeps back. Nine out of ten times the swing circuit is losing pressure somewhere between the pump and the motor — and the motor's case drain tells you where.
What it usually is
| Share of cases | Cause and how to check it |
|---|---|
| 36% | Swing relief pressure set low, or relief valve leaking Tee a 0–60 MPa gauge into the swing relief port, hold against a stall, compare with the rated 34.3 MPa. |
| 30% | Swing motor worn internally Measure case-drain flow with the motor at relief: over 8–10 L/min at 1,800 min⁻¹ means the piston group is done. |
| 18% | Parking brake not fully released Check pilot pressure at the brake release port — it must reach the value in the catalogue, and the brake must open within 0.5 s. |
| 16% | Centre joint (swivel) seals leaking Compare motor inlet pressure with pump outlet pressure at the same moment; a gap that grows with oil temperature points at the joint. |
Field tests
1. Gauge, not guesswork
Tee into the swing relief port at the valve block. Record: stall pressure, pressure at first movement, and pressure after 10 minutes of work.
2. Case drain
Run the motor at relief for 60 s with the drain hose into a measuring container. Flow, not pressure, is the wear signal.
3. Brake release
Listen and feel: a brake that drags heats the housing to 70 °C+ within 15 minutes of work.
What actually fixes it
A seal kit restores a dry motor. A worn piston group is a motor or a sub-assembly, not a kit — ask for both numbers on one quote and compare against a day of downtime.
Send the plate, get the variant in writing.
One photo of the nameplate and one of the pump from the side. We confirm the variant, then quote — the price holds for seven days.