← All faults
The pump growls, whines or knocks
Pump and pressure. Sound is the cheapest sensor on the machine. A growl that disappears when the machine is cold is air; a knock that follows load is metal. Identify which before you take the pump off.
Probable causes
Cavitation: suction strainer clogged or air ingress
Vacuum gauge at the pump inlet: over −0.02 MPa means a restricted suction. Look for foam in the tank.
Worn piston shoes / slippers (metal on metal)
Cut the filter open. Brass-coloured particles mean shoes; steel flakes mean cylinder block or valve plate.
Shaft seal letting air in
Oil weep at the shaft, or a whistle at idle that stops when the case is pressurised.
Coupling or alignment
Hand-turn the pump with the engine off: roughness in a quarter-turn means coupling, not hydraulics.
Test before you buy
Cold start listening
Record the first 30 seconds after start with a phone. Cavitation noise is loudest when the oil is thick.
Inlet vacuum
Tee a vacuum gauge before the pump. A new strainer should read under −0.01 MPa at full flow.
Case drain and filter cut
Both together separate air from metal in five minutes.
circuit schematic · test points
Three points that settle the argument about the cause: pump pressure, motor inlet pressure, and case drain.
FL-WS-PUMP-Nrev 2024-11-25source: FLUTEK catalogue
Workshop worksheet
| Reading | Where | Expected | Recorded |
|---|---|---|---|
| Pump pressure | TP1 | catalogue | |
| Motor inlet pressure | TP2 | catalogue | |
| Case drain | TP3 | ≤ 8–10 L/min |
The principle behind it
What fixes it
One quote, three options
A seal kit, a sub-assembly and a complete unit are three different prices for three different amounts of work. Ask for all three on the same sheet and decide with the downtime cost in front of you.
A pump that is cavitating is not a worn pump — replacing it without fixing the suction kills the new one too. That is the conversation this page exists to start.
Ask for the price
