Hydraulic Cylinder Repair
Reseals, rod checks and an honest view on whether it is worth repairing.
Cylinders fail slowly, which is why they get ignored. A ram that weeps a little, or drifts down a few inches overnight, still works. It carries on working right up until it does not, usually while loaded.
Diagnosis before parts
A large share of cylinders we are asked to reseal do not need resealing. The symptom, most often a ram that will not hold position, has several possible causes and only one of them is inside the cylinder.
Isolating the cylinder settles it in a few minutes. If the ram holds when the service line is blocked off, the leak is past the piston seal and the cylinder is the problem. If it still drifts, the oil is going back through a valve and a seal kit would have been money spent for nothing.
What a proper reseal involves
- Cylinder stripped, all seals removed and the bore and rod cleaned and inspected properly rather than glanced at.
- Rod checked for pitting, scoring and straightness. Chrome damage is what kills a fresh seal, so this decides whether a reseal is worth doing at all.
- Bore checked for scoring and honed where it will clean up.
- Full kit fitted: rod seal, wiper, piston seal, bearing rings and the static seals, not just the one that was visibly leaking.
- Reassembled clean, then function and leak tested before it goes back on.
When we will tell you not to bother
There is a point where a cylinder is not economic. A deeply pitted rod, an oval or scored bore, or a barrel that has been welded and distorted will all shorten a reseal to a matter of weeks. Where that is what we find, you get told, with the reason, so you can price a replacement instead. That is a smaller job for us and the right advice for you.
What is included
- Diagnosis first: a cylinder that drifts is not always a cylinder problem, and a new seal kit will not fix a leaking control valve.
- Full seal kit replacement including rod seal, wiper, piston seal and bearing rings.
- Rod inspected for pitting, scoring and straightness before anything is reassembled.
- Bore honed where it will clean up, and a clear answer where it will not.
Common questions
My ram creeps down under load. Is that the seals?
Not necessarily, and this is worth diagnosing before spending money. A cylinder that drifts can be a worn piston seal, but it can equally be a leaking service valve, a failed check valve or, on an excavator, a worn spool. We isolate the cylinder to find out which before recommending anything.
Is it cheaper to reseal or replace?
For most excavator and tipper cylinders a reseal is a fraction of the cost of a new unit, and that is usually the right answer. Where the rod is badly pitted or the bore is scored, a reseal will fail again quickly and we will tell you a replacement is the better spend.
Can a cylinder be resealed on site?
Sometimes, for a straightforward accessible ram in clean conditions. More often it should come off, because a cylinder is a precision fit and rebuilding one in a muddy compound is how grit gets into the bore. We will be straight with you about which situation you are in.
How long does a reseal take?
Typically a day or two once the cylinder is off, depending on seal kit availability. On less common industrial rams the kit is the long lead item rather than the work.
The rod is scored. Does that scrap the cylinder?
Light scoring often polishes out. Deep pitting through the chrome does not, and a new seal running on a damaged rod will be leaking again within weeks. Rods can sometimes be re-chromed or replaced, which is worth pricing against a new cylinder.
Machine down? We can usually be with you the same day.
Tell us the machine, the hose and where you are. We will tell you honestly whether we can reach you and what it will cost before we set off.