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HKM

Breaker Troubleshooting Guide

Hydraulic Breaker Not Striking

The breaker is completely silent or strikes only occasionally. Causes are listed by likelihood: start with the most common and easiest to check.

← All symptoms

First checks on site

  1. 1Lower the breaker to the ground, secure the carrier and release hydraulic pressure.
  2. 2Disconnect the quick couplers and reconnect them until fully seated. A half-seated coupler can cut off flow completely while looking perfectly connected from the outside; this is the single most overlooked cause on site.
  3. 3Check the hydraulic oil level and the control circuit (foot pedal or lever): is the breaker line actually being engaged?

Causes and how to tell them apart

1.Hydraulic flow is not reaching the breaker

Is this the one?
The breaker is completely silent; no sound or vibration when the control is engaged. If a gauge is fitted, pressure does not build.
How to check
Disconnect and reconnect the couplers. Confirm the control circuit opens the breaker line; if the carrier has a separate breaker circuit switch, check that it is on.
What to do
If couplers and controls are sound, have the directional valve and relief valve setting checked. At this point the fault is most likely on the carrier side, not in the breaker.

2.Seizure at the tool, retaining pin or bushing

Is this the one?
The breaker sounds like it is running but the tool does not move; moved by hand the tool has no normal play and sits seized.
How to check
Remove the tool. Look for mushrooming on the tool shank, deformation in the retaining pin seat or excessive bushing wear. Check that the tool enters and leaves its seat freely.
What to do
Grind or replace a mushroomed tool; renew a deformed retaining pin. If the bushing is worn the tool runs off centre and the seizure will return, so replace the bushing at the same time.
Related part →

3.Nitrogen pressure too high

Is this the one?
Circuit is sound, tool is free, yet the breaker does not strike at all or stops after a few blows. Pressure builds but there is no piston movement.
How to check
Check the gas chamber pressure. The correct value varies by model; consult the operating manual for your model or ask our service team.
What to do
Release the excess gas following the procedure in the manual. The gas chamber is pressurised; the work must be done by someone with the right equipment and procedure.

4.Valve sticking or contaminated hydraulic oil

Is this the one?
The breaker runs intermittently, sometimes catching and sometimes not striking at all. The oil is dark or smells burnt, or the filter fills quickly.
How to check
Inspect an oil sample and the filter condition. Check the circuit for signs of metal particles.
What to do
Change the oil and the filter. Contaminated oil will make the valve stick again; cleaning the valve alone brings the problem straight back.
Related part →

5.Piston seizure or internal damage

Is this the one?
Everything above has been eliminated and the breaker still does not strike. On disassembly the piston surface shows scoring, heat marks or chrome flaking.
How to check
At this stage diagnosis requires disassembly. Field checks are exhausted.
What to do
Send the breaker to a service workshop. Piston surface damage is usually the result of contaminated oil or sustained blank firing; unless the cause is removed, the replacement will meet the same end.
Related part →

When to stop

  • Do not attempt to open the body without discharging the gas chamber.
  • Do not force the circuit to warm the breaker while it is not striking; if there is internal leakage the oil temperature will rise fast.
  • Do not replace the piston or valve before the cause is found; the same cause will destroy the new part.

Frequently asked

The breaker does not strike at all but the machine works normally. What could it be?

The most common cause is a quick coupler that is not fully seated: it looks connected but passes no flow. Second is a control circuit that is not opening the breaker line. Once those are eliminated, check tool seizure and nitrogen pressure.

Why does high nitrogen pressure stop the breaker striking altogether?

The pressure in the gas chamber works against the return of the piston. Excessive pressure prevents the piston from completing its stroke, so the breaker either does not strike or stops after a few blows. Low pressure produces the opposite: fast but weak striking.

The breaker strikes sometimes and not others. Is that normal?

No. Intermittent operation usually points to valve sticking caused by contaminated oil. Cleaning the valve without changing the oil and filter brings the fault back quickly.

Related symptoms

Breaker Striking Weakly

It strikes but has no power; it will not break the material and the blow sounds thin.

Hoses Vibrating and Jumping

Hoses vibrate heavily and jump; a pulsation is felt in the circuit.

Send us the symptom and your machine model; our service team will walk through the field steps with you. Brand does not matter — we supply parts and service support for all breaker makes and models.

Ask our service team