Hydraulic Cylinder Leaking: Reseal, Rebuild or Replace?

Start by finding where it leaks

Before you decide anything, clean the cylinder and watch it. Wipe it down, run the machine through a few cycles, and see where the oil appears. The location tells you which part of the cylinder is failing, and that points toward the right repair.

• Oil at the rod end, where the rod comes out of the gland: this is usually the rod seal or wiper, and sometimes a damaged rod.
• No outside leak, but the cylinder drifts or loses force under load: the piston seal is probably letting oil bypass inside.
• Oil at the ports or fittings: often just a fitting, an o-ring or a hose end. Check these before blaming the cylinder.
• Oil along the tube or at a weld: a cracked weld or a pitted tube, which is more serious.

When a reseal is enough

A light weep at the rod, on a cylinder that otherwise moves smoothly and holds position, is the classic case for new seals. Seals are wear items. They harden with age, heat and contaminated oil, and eventually they stop sealing even though the metal parts underneath are fine. A reseal means taking the cylinder apart, cleaning it, replacing the seals and wipers with the correct kit, and putting it back together.

The key word is correct. Seal kits are matched to bore, rod diameter and groove size, and the wrong profile can leak on day one or wear out fast. Bring the cylinder in, or at least the details we covered in the parts counter article, and the seals can be matched to the actual hardware. C & C Hydraulics offers seal kits and repair, and customers' reviews mention seals being found and installed on their cylinders.

When you need a full rebuild

A rebuild goes further than new seals. The inside of the cylinder gets inspected, and worn or damaged parts are repaired or replaced. Signs that you're past a simple reseal include:

• Scratches or pitting on the chrome rod. A scored rod cuts a fresh seal in short order.
• A rod that's bent. Hold a straightedge along it, or roll it on a flat surface and watch for a wobble.
• A scored or bell-mouthed tube, where the piston has scraped the inside wall.
• Seals that fail again soon after a reseal, which suggests the surface they run against is damaged.
• Metal flakes or glitter in the oil, which means something inside is wearing against something else.

C & C lists rods and tubes, seals, and hydraulic cylinders among its repairs, and it has a full machine shop in the building. That matters because a damaged rod or tube is often a machining and welding job rather than a part you order from a catalog. Whether a particular rod can be saved is a question for a technician looking at it in person.

When replacement makes more sense

Sometimes repair isn't the right call. A tube that's cracked, a body bulged from pressure, or a cylinder so worn that every repair is a temporary fix may be better replaced. Replacement can also be the answer when the cylinder has been modified over the years and no longer matches any standard part.

Replacement doesn't have to mean a catalog cylinder. C & C Hydraulics can manufacture custom cylinders to meet your needs. If the old cylinder is obsolete, the dimensions are unusual, or you want a different mounting style, a custom build can match what the machine actually needs. Their cylinder list is wide: tie-rod, welded, telescopic, multi-stage, heavy duty mill type, crane, forklift repair cylinders, marine, and more.

What to bring or tell them

To get a straight answer on reseal, rebuild or replace, bring the cylinder if you can carry it. If it's too heavy, collect the numbers: bore, rod diameter, stroke, closed length, mounting style and port size. Take photos of the rod surface and the leak area. Then describe the symptoms in plain terms: does it leak, drift, move slowly, chatter or lose power under load?

Also tell them about the machine's job. A log splitter, a dump trailer, a lift and a loader all put different demands on a cylinder. And mention anything you've already tried. If you replaced a hose or a valve and the problem stayed, that points the finger back at the cylinder.

A note on safety

Never work on a cylinder that's holding a load. Lower the load fully, shut the machine off, and relieve pressure in the lines before you loosen any fitting. Support anything the cylinder was holding up with proper stands or blocking, not with the cylinder itself. A leak at a pinhole can spray fluid at high speed, so use a piece of cardboard to find leaks rather than your hand.

Get it looked at

If you're unsure which category your cylinder falls into, bring it in or send details. Call C & C Hydraulics at (860) 582-0308 or email sales@cchydraulics.com. The shop is at 116 Wolcott Rd. in Terryville, and it has served New England since 1973. A technician can look at the rod, the tube and the seals, and tell you which repair makes sense for the machine you're running.