35 Years of Hydraulic Expertise  ·  Old-School Communication.  New-School Service.

978-368-3325
Compactors & Balers · Hydraulic · H-8

Your Pump Is Screaming. Shut It Down.

A pump that whines, screams or knocks is starving for oil. It is cavitating — pulling vapour instead of fluid and hammering itself apart from the inside. This is the one symptom on this site where the correct first action is to shut the machine off. A cavitating pump destroys itself in hours, not weeks.
Get a Technician Out Now — 978-368-3325
All Hydraulic Symptoms
Tier 1 action: shut it down. Everything else is Tier 3.
Right Now

This Is a Shutdown, Not a Diagnosis

Almost everything else on this site can wait for a scheduled visit. This one cannot, and the reason is that the damage is happening while you decide.

Stop the machine.

Not after this container. Now.

Lock it out.

So nobody starts it again while it waits, which is what always happens otherwise.

Put a sign on it.

“Do not run — pump fault, service called.” A dock crew will start a compactor that looks fine.

Check the sight glass while you wait.

Low oil is the most common cause and it tells the technician what to bring.

Call it in as urgent.

A pump caught in the first hours is often still a strainer and filter service. The same pump tomorrow usually is not.

Why running it “just to finish the load” is the expensive choice

Cavitation is vapour bubbles collapsing against metal at high pressure, thousands of times a second. It erodes the pump’s internal surfaces and puts the debris into the oil, where it then circulates through the valve and the cylinder. Finishing one more container can turn a filter change into a pump, and sometimes into a pump plus everything downstream of it.
Reading It

What the Noise Is Telling You

All three sounds mean the same category of fault, but they are not the same stage of it.

A rising whine

The early version. Usually a restriction on the suction side — a strainer loading up, or oil too heavy for the temperature. Caught here it is often a service, not a replacement.

A scream

Full cavitation. The pump is running dry enough to be damaging itself continuously. Shut it down.

A knock or rattle

Mechanical. Either cavitation that has progressed to internal damage, or a failing coupling or bearing. Either way, off.

Normal is not silent

A hydraulic pump under load makes noise, and a compactor is a loud machine by nature. What matters is change — a sound that is new, or rising, or that appears at a particular point in the cycle. Nobody knows that machine’s normal sound better than the people who work beside it every day.
Narrowing It

Five Causes, Cheapest First

  • Clogged suction strainer — The classic, and the cheapest. The pump is trying to pull oil through a screen that is no longer open. Service, not replacement — if you catch it.
  • Low oil — The pump is pulling air along with the oil. Top it off, then find the leak that emptied it.
  • Partly closed suction valve — A valve not fully reopened after service. Free to fix and it will destroy a pump.
  • Oil too heavy for the temperature — A summer-weight oil meeting a New England January is a suction restriction the machine did not have in July.
The Clock

What It Costs Per Hour

The repair on this symptom is priced almost entirely by how long the machine ran after the noise started.

First hours

Strainer and filter service, oil change, find and fix the suction restriction. The pump survives.

Same day

Pump showing wear. It may be limping for months afterward with reduced output, which shows up later as slow cycling and weak packing.

Days

Pump replacement, plus flushing the debris it shed out of the valve and cylinder. The most avoidable large invoice on this site.
Before You Call

What We Need to Quote It

You do not need all of this — the make and model plus photos is usually enough to get started. But the more of it you have, the closer the first number is to the final one.
  • Bore — Inside diameter of the barrel. Stamped on many data plates; otherwise we measure it.
  • Stroke — Fully extended length minus fully retracted length.
  • Rod diameter — Across the chrome, measured with calipers if you have them.
  • Mount type — Clevis, cross-tube, trunnion or flange — and the pin diameter.
  • Pin-to-pin retracted — Center of one mounting pin to center of the other, ram fully in.
  • Ports — Size, thread type, and whether they face the same direction or opposite.
  • Machine make and model — Off the data plate. It often tells us the cylinder before you measure anything.
  • Photos — The whole cylinder in place, both mounting ends, and a close shot of the rod.

If you can't get the measurements

Don’t climb on the machine to get them. Send the make, the model and the photos, and we will take the dimensions when the cylinder is out — or bring a replacement with us if we already know that machine.
Safety

Where Your Checking Stops

Tier 1 · Site check

Shutting the machine down, locking it out, tagging it, reading the sight glass.

Tier 3 · Service technician

Opening the suction line, pulling the strainer, testing pump output, and pump replacement.

Do not crack a fitting to check for pressure

Stored hydraulic energy is the hazard that makes this Tier 3 no matter how simple the repair looks. Loosening a fitting “to see if there’s still pressure in it” is how people get injection injuries — which do not look serious for the first hour and are a surgical emergency. Pressure gets relieved deliberately and confirmed at the gauge.
Applies To

Compactors and Balers Both

This fault lives in the power unit, so it behaves the same on a stationary compactor and on a vertical baler. One difference is worth naming.

On a baler

Identical, and arguably more urgent: a baler in a retail back room is usually the only one on site, and when it goes down the cardboard has nowhere to go within the hour.
Questions We Get

Pump Noise, Answered

It only whines when it's cold in the morning. Is that still cavitation?
It is, and it is the mildest version — oil too thick to pull freely until the system warms. It is still a suction restriction and it is still wearing the pump every cold start. The fix is usually the right oil for the season rather than a repair.
Not necessarily. A strainer can partially clear, a cold system warms up, oil settles. The condition that caused it is still there and it will come back. A noise that comes and goes is an early warning, which is the best kind to get.
If the sight glass is low, adding oil is the right immediate move and it may quiet the pump completely. But the oil left somewhere, and a machine that runs itself low again is going to do this a second time.
Same day. This is the symptom we would rather you call about at 10pm than wait on until Monday, because the difference between those two calls is usually the price of a pump.
Get It Running

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978-368-3325

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Find us

T&T Weber Hydraulic Inc.
184 Stone St, Unit 5
Clinton, MA 01510

Where we go

Onsite compactor and baler service throughout New England — Massachusetts, Connecticut, Rhode Island, New Hampshire, Vermont and Maine. Cylinder reseal and replacement, domestic replacement cylinders, hydraulic, electrical and controls, and full mechanical repair.