TL;DR — A refuse ejection cylinder that extends but will not push waste out usually means an internal piston-seal bypass, not a dead system. Before you order a replacement, measure three things the body actually cares about: bore, stroke, and the pin-center distance between the mounting eyes. Miss the pin centers by a few millimetres and the blade will not travel its full stroke or the rod will bottom on the wrong face. Get those three numbers right and a drop-in replacement is a parts order, not a re-engineering job.
Why the ejector is the least understood cylinder on the truck
The packer gets all the attention because it cycles constantly. The ejector sits idle for most of a route and then has to shove six to ten tonnes of compacted waste out of the body in one long, slow push. That push is the hardest single job on the whole truck, and it happens cold.
When an ejector cylinder fails, the symptom is almost always the same: the rod extends, the blade moves a little, then it stalls with the hopper still half full. Drivers describe it as "no power at the back." What they are really describing is a piston seal that has given up after years of sitting in the same spot with grit in the oil.
Three numbers that decide whether a replacement fits
A refuse body is built to a drawing, and the drawing sets the cylinder's envelope. Three dimensions do most of the work.
| Dimension | What it controls | What goes wrong if you guess it |
|---|---|---|
| Bore | Push force at working pressure | Undersized bore stalls under a full body |
| Stroke | How far the blade travels | Too short leaves waste trapped; too long bottoms the rod |
| Pin-center length (retracted) | Whether it bolts into the same eyes | A few mm off and the eyes will not line up |
| Rod diameter | Column strength under long push | Too thin a rod buckles on a full eject |
Measure the bore and stroke from the old unit, not the manual
Take the bore off the tube, not off a parts book. Refuse bodies get re-bodied and re-fitted over a decade of service, and the manual you have may describe a different build than the one on the chassis now. A set of inside calipers on the tube, or a piston measurement once it is apart, settles the bore.
Stroke is the difference between the fully extended and fully retracted pin centers. Mark the rod at full extension and retract it, then measure between the marks. This is the number drivers and fitters argue about most, because a few millimetres of lost stroke means the last half tonne of waste does not clear the tail.
Pin centers are where drop-in replacements die
The pin-center distance — from the eye of the base to the eye of the rod end, measured with the cylinder retracted — is the dimension that catches people. A bore and stroke can be perfect while the mounting eyes are 12 mm too close together, and the cylinder simply will not pin into the same brackets.
Measure it on the old cylinder with the rod fully retracted, eye center to eye center. If the old unit is bent or too far gone to trust, measure between the mounting lugs on the body and work backward. A photo of the cylinder in place, with a ruler held against it, saves a round of questions.
Internal bypass is the real failure, not the tube
Most ejection cylinders that come back to us have a clean, straight tube and a piston seal that is torn or flattened on one edge. The rod extends because the pump still builds pressure, but the oil slips past the piston and the blade never gets the full push. There is no external puddle to find, which is why these failures drag on.
The test is a deadhead. Run the rod out until the blade seats against the ejector face and hold the valve open. If the blade creeps back toward home while the gauge holds pressure, the piston is bypassing. If the tube mic's round and unscored, a reseal is honest work. If it is scored or swollen, a new seal is a bandage that fails in a few hundred cycles.
Single acting or double acting: match it to the valve
Refuse bodies run both. A double-acting ejector powers the blade out and pulls it back to home, which needs a four-way directional valve. Some compact rear-loaders and front-loaders use a single-acting cylinder that extends under pressure and returns on a spring or by gravity. The acting type is not visible from the outside, and it is the easiest thing to order wrong.
Count the ports. One working port plus a breather means single acting. Two working ports means double acting. Order the wrong acting type and the replacement will fit the brackets but will not function, no matter how clean your measurements are.
Order the replacement the way the body was built
We build refuse truck cylinders and compaction station hydraulics to ISO 6020 and 6022 geometry, and pressure-test every unit before it leaves the floor. When the original part number is obsolete or the body has been re-bodied, our custom and OEM replacement service works from a drawing, a worn sample, or six measurements. Quote in 48 hours, one sample minimum, 45 to 60 days for the first article, and an 18-month warranty with a full seal and service kit.
If the fault turns out to be upstream — a tired pump or a valve that will not shift — the same pressure and flow logic applies, and the drive side sits on our power-unit range at trailerhydraulic.com. When you are comparing bar and PSI across a European body, our pressure converter keeps the two honest. For the telescopic side of a multi-stage ejector, see the note on telescopic cylinders on hcictec.com.
Frequently asked questions
What measurements do I need to order a replacement ejection cylinder?
Send six numbers: bore, stroke, retracted pin-center length, rod diameter, the mounting style at each end, and the working pressure. A photo of the worn cylinder on the body helps more than the original part number, because bodies are re-bodied over their life and the number may no longer match. If you can send the old unit, HCIC reverse-engineers from the sample.
Why does my ejection cylinder extend but not push the waste out?
Almost always an internal piston-seal bypass. The cylinder builds pressure against a blocked port but oil slips past the piston, so the rod extends with no force behind it. A load test — deadhead the rod against the blade and watch for the blade creeping back — confirms it. A scored bore tears the new seal within a few hundred cycles, so measure the tube before you decide to reseal.
Is an ejection cylinder single acting or double acting?
Both exist on refuse bodies. A double-acting cylinder powers the eject in both directions and needs a four-way valve, which is why a body can push the blade out and pull it back to home. Some compact rear-loaders use a single-acting cylinder that extends under pressure and returns by spring or gravity. Match the acting type to your valve, or the replacement will not function even if the dimensions fit.
How long does a replacement ejection cylinder take to build?
HCIC quotes within 48 hours once you send bore, stroke, pin centers and quantity. A first-article sample ships in 45 to 60 days; batch orders of 50 pieces or more run 30 to 45 days. One sample minimum, 18-month warranty from shipment, and a full seal and service kit is supplied with the cylinder.