Check the rod for scoring and the bore for damage before ordering seals. Measure drift to confirm the cylinder is actually bypassing internally, and check the gland and wiper for wear. A scored rod destroys new seals quickly, so it must be addressed in the same job.
How to confirm it
- Confirm the cylinder is actually the fault
Test drift with a known load at operating temperature, then cap the cylinder ports and repeat. If the drift stops with the cylinder isolated, the cylinder is bypassing internally. If it continues, the holding valve or the spool is responsible and the cylinder does not need to come apart.
- Inspect the rod over its full stroke
Extend and retract the cylinder fully and examine the entire rod surface for scoring, pitting, rust or chrome damage. Damage in the middle of the travel affects seals every cycle; damage near the end affects them less often. Any deep scoring will destroy new seals and must be repaired or the rod replaced.
- Examine the gland, wiper and wiper area
Look for external weeping, a hardened or damaged wiper, and dirt packed into the gland. A failed wiper lets abrasive material into the seal, which is one of the main reasons a rod scores in the first place.
- Check the bore where it can be seen
On cylinders where the bore is accessible, look for scoring, corrosion and pitting. Bore damage cannot be corrected by seals and may require honing or a new tube, which changes the repair decision entirely.
- Check the rod for straightness and the pin bosses for wear
A bent rod loads the gland unevenly and causes repeated seal failure. Worn or oval pin bosses cause side loading for the same result. Both are better addressed while the cylinder is off the machine.
- Decide the repair before ordering parts
Seal kit only: rod and bore sound, gland and wiper the only wear. Seal kit plus rod repair: rod scored or chrome damaged. Replacement or re-tube: bore damaged beyond repair. Each decision depends on what the inspection just found, so the inspection must come first.
- Order the seal kit against the cylinder identification, not the machine model
Cylinder variants change across serial number breaks and build years. Read the number stamped on the cylinder or from the machine's parts documentation for the specific serial number, and quote that when ordering.
What to do about it
Rod and bore sound: a seal kit is the repair. Clean the components thoroughly, protect the rod during reassembly, and use assembly lubricant on the seals rather than dry fitting them.
Rod scored or chrome damaged: have the rod repaired or replaced at the same time as the reseal. Fitting new seals to a damaged rod produces a leak again within a short time, and the second repair costs more than doing it once.
Bore damaged: the tube needs attention. Establish the cost of repair against the cost of a replacement cylinder before deciding, because on smaller cylinders replacement is often the better value.
Bent rod or worn pin bosses: address them in the same job. Reassembling a cylinder onto worn bosses introduces side load that will fail the seals again.
Need the parts this covers?
Send the machine model, serial number and the part numbers you need. We confirm fitment before payment and state the grade of every line — genuine, OEM-quality or aftermarket.
Request a quoteFrequently asked
Can I replace cylinder seals myself?
On smaller cylinders, yes, with care and with the right tools. The critical points are cleanliness, protecting the new seals during assembly and ensuring the rod is undamaged. On large cylinders the handling equipment is the practical constraint.
How do I know if my rod needs replacing?
Scoring deep enough to catch a fingernail, chrome flaking, or pitting and rust will all damage seals. Light polishing marks are usually acceptable. If in doubt, send photographs of the rod — the decision is visual and easy to advise on.
Why did my new seals fail again quickly?
Almost always one of three causes: a damaged rod, a damaged bore, or contamination in the oil damaging the seal. Resealing without addressing the cause of the first failure simply repeats the repair.