Hydraulic door pack — slow, creeping or noisy mixer door
Symptom
The mixer door opens slowly, does not move, creeps open or closed, the pump whines, the oil foams, runs hot or turns milky, or a hose bursts.
Likely causes
- Low oil level, blocked suction strainer or air leak on the suction.
- Worn pump, or relief valve leaking or set wrong.
- Burnt solenoid coil or sticking spool.
- Check valve or cylinder seals leaking (door creeps).
- Water in the oil from a bad breather or filler cap (milky oil).
- Wrong hose rating, chafing hoses or pressure spikes.
Most likely and cheapest to check first.
Checks
- Oil level in the sight glass; oil colour - milky means water, dark and burnt-smelling means overheating.
- Working pressure on the gauge against the value on its label.
- Watch the door with the pump off. If it moves, a check valve or cylinder seal leaks.
- Inspect hoses with a piece of cardboard, never with your hand.
Fix
- Top up with the specified oil (often ISO VG 46) through a filter.
- Clean the strainer; seal the suction; service or reset the relief valve.
- Replace the coil or valve; reseal the cylinder or replace the check valve.
- Change oil and filters (about every 2,000 h or yearly); replace the breather.
- Replace hoses with the correct rating, routed and clamped so they cannot chafe.
Stop the equipment if
Oil is spraying from a hose or fitting. Stop, isolate and depressurise before going near it.
Parts you may need
Isolate stored energy
Before working on any hydraulic circuit: isolate the motor, lock the isolation valve, release pressure in the circuit, any accumulator and any load held up by a cylinder, lock the bleed valve open, and verify the gauge reads zero.
DANGERA pinhole leak can inject oil through the skin; injection injuries have been reported at pressures as low as about 7 bar and can lead to amputation. An accumulator keeps pressure even with the pump stopped. Release its pre-charge before opening it.
FIELD TIPEvery operator should know where the hand pump is and how to open the door with it. Return its lever to the centre after use, or the door may not work on the next power failure.
⚠ Every check inside a machine starts with full lockout. Safety disclaimer