Blog / Hydraulics
Hydraulic cylinder leaking: when to replace the seal kit
Hydraulic cylinders move the boom, bucket and loader arms. Inside each cylinder is a seal kit that keeps oil from escaping and stops oil passing from one side to the other inside the cylinder. Over time and with dust, the seals wear.
Signs a cylinder needs seals
- Oil on the chrome rod or a ring of oil around the cylinder head: an external leak.
- The boom or bucket slowly drifts down with the machine off or idle: usually an internal leak.
- Weak movement in one cylinder while the others are normal.
- Dust and mud sticking to the rod because of the oil.
Check the rod before the seals
The chrome rod must be perfectly smooth. If it has scratches, rust, dents or a bend, new seals will be cut quickly and leak again. In that case the rod needs repair or re-chroming before new seals.
How to order the right kit
- Identify the cylinder: bucket? dipper? boom lift? loader? and which side.
- Note the machine model and serial number.
- If you can, measure the rod diameter and the cylinder bore (for example 60×110 mm).
- If there is a number on the cylinder body, photograph it and send it.
⚠️ A cylinder holds the weight of the boom. Never dismantle a cylinder before lowering the boom to the ground or supporting it safely, and releasing the system pressure.
Tip
A small leak left unrepaired lets dust into the cylinder and damages the rod and bore from inside, turning a cheap seal kit into an expensive repair. Fix it early.
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