Why Are Oil Cooling Systems Necessary?

Oil cooling systems remove the heat that builds up in a machine so that the oil and the parts around it stay at a safe temperature. This article explains which problems appear when cooling is missing or inadequate, which signs point to them and what direction to take.

Consequences of overheating

Problems often develop in a chain rather than at a single point.

• Oil breakdown: High temperature speeds up oxidation of the oil. It can thicken, leave deposits and lose its protective properties.
• Loss of viscosity: Heated oil thins. The lubricating film between moving parts weakens and wear increases.
• Seal hardening: Elastomer seals and hoses harden, lose flexibility and may begin to leak.
• Loss of efficiency: Internal leakage increases in pumps and valves; the machine does the same work more slowly or with more difficulty.
• Failure: Early wear and unplanned downtime can occur in components such as pumps, valves and cylinders.

Heat buildup does not do its damage in one go; with every work cycle it takes a small share out of the life of the oil and seals. For this reason the problem is often noticed months later, not as a single failure but as a string of maintenance needs. Not having a cooler does not remove the cost; it only postpones it to a later date and often to a larger intervention.

The effect of temperature on thermal aging should also be considered: oil degradation is a self-reinforcing process. Degraded oil carries heat less well, the lubricating film weakens, friction rises and more heat is produced. Once this cycle has started, it generally does not stop on its own without added cooling.

Signs that cooling is inadequate

• Tank or hose surfaces that are unusually hot
• Oil that has thickened, darkened or smells burnt
• The machine slowing down and losing power during long runs
• New leaks starting at seals and connections
• The temperature gauge or warning light coming on frequently
• Problems becoming more pronounced in summer or during heavy shifts

Any one of these signs on its own does not give a definite answer; they can have other causes. But if several appear together, measuring the oil temperature is a good first step.

The way forward

1. Measure the temperature: Compare the actual oil temperature with the range the machine manufacturer allows.
2. Check the existing cooler: The fins may be clogged with dust, oil or mud; the fan and airflow should also be reviewed.
3. Evaluate the capacity: If the cooler is undersized for the heat load, or there is none at all, a suitable cooler is needed.
4. Check the oil condition: Oil that has been hot for a long time may need to be changed.

These steps are meant as a guide for the user. Because every machine has a different heat load, rely on the manufacturer's documentation for exact values.

Which machines are at higher risk?

• Hydraulic power units that run continuously through long shifts
• Compressors working in hot weather or in an enclosed compartment
• Construction machinery and forklifts that are constantly under load
• Systems whose fins are coated with dust and oil and whose maintenance is lacking

The common point is that heat generation exceeds heat rejection. In such a case, instead of blaming the machine, you need to look at the heat balance.

Next step

You can find what a cooler adds to a system in the article advantages of hydraulic oil coolers, and a wider treatment of the symptoms in the article how to tell a radiator is failing. For a suitable cooler, see the fan-cooled radiators page; for product selection and technical information, contact us.