← All faults
Hydraulic oil runs hot
Heat. Heat is a symptom of lost energy, and in hydraulics lost energy is a leak — usually an internal one. The oil cooler is the last suspect, not the first, and it is the one everybody replaces first.
Probable causes
Internal leakage in motors or pump (worn groups)
Case-drain flow on each motor and the pump. One hot circuit narrows the search to one unit.
Cooler blocked or fan / hydraulic-driven fan weak
Infrared the cooler inlet and outlet: a working cooler drops 10 °C or more across.
A relief valve blowing continuously
Watch pressure at idle with no function commanded — it should be standby, not relief.
Wrong oil grade or contaminated oil
Viscosity at 40 °C and water content; a 10 °C ambient swing needs a different grade.
Test before you buy
Temperature map
An infrared camera on the tank, each motor housing and the valve block after 30 minutes of work. The hot unit names itself.
Case drain again
Heat and case drain are the same measurement seen two ways.
Oil sample
A 100 ml sample sent for water, viscosity and particle count answers three causes at once.
circuit schematic · test points
Three points that settle the argument about the cause: pump pressure, motor inlet pressure, and case drain.
FL-WS-OIL-OVrev 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.
Overheating is usually a repair-kit conversation, not an assembly conversation — which is why it is worth diagnosing before ordering.
Ask for the price
