Your Mini Excavator Is Not a Hot Tub — Let’s Talk Overheating

It’s summer break, your mini digger is working as it should, and suddenly — it’s hotter than a Dutch oven. If only your hydraulic system could talk, it’d be screaming, “I’m melting!”

Overheating isn’t just inconvenient — it’s a performance killer. And if you’re in the business of moving dirt (or moving sales), a few degrees can make or break your day — and your equipment.

These are some real consequences of overheating:

1. Overheating = underperformance. Hydraulic fluid works best between 50°C and 80°C. Hydraulic fluid oxidises and may start foaming, losing its lubricating properties. Performance can sink by up to 35% as fluid temperatures rise from 60°C to 100°C.
2. Overheating is also a cause of long-term machinery failure. Loss of oil viscosity → micro-friction that can quickly wear down internal components. Cavitation can damage hydraulic pumps, causing increased noise. Seals and valves may expand, degrade, and leak.
3. In extreme cases, heated fluid leaks can burn operators. Ouch — literally and financially.

These may be some early signs that your mini digger is having a heat stroke:

1. Inconsistent, slowed or decreased power in the hydraulic movements of the boom, arm, or attachment
2. Unusual noise from the hydraulic pump or excessive vibration caused by vapour bubbles
3. Foamy or milky hydraulic fluid
4. It just feels too hot
5. Some machines have an audible alarm to notify you when your equipment is nearing dangerously high temperatures

What you can do about it

• Stop the machine immediately — don’t continue operating while hot and don’t ignore the warning signs.
• Use high-quality hydraulic fluid with a good viscosity index. A high viscosity index means the fluid resists thinning when hot and thickening when cold. This keeps your hydraulics working smoothly during cold starts and stable under heat stress. Coolant fluids last a long time and are critical to performance, so it’s important to invest in high-quality fluid. You should also ensure that you change your coolant every 1,000 hours, or every two years (whichever comes first). Old or oxidised fluid loses its cooling/lubricating abilities. You can also flush and change earlier if the fluid looks questionable, such as being foamy. Ensure that you never mix multiple coolant types, as, for example, adding a propylene glycol-based coolant to ethylene glycol coolant can create a gelling reaction, damaging the radiator and potentially the entire engine. Ensure that the level of hydraulic fluid is also correct, as low or overfilled hydraulic oil can both cause overheating.
• Check and clean filters regularly — don’t let gunk accumulate. Most filters should be replaced every 500 hours of usage time or every year (whichever comes first). Similarly, you should inspect the cooling systems: radiators, fans, and shrouds, to ensure they aren’t clogged with dust, dirt, or mud. If they are, blow out debris with compressed air, or gently wipe them down when they are cool. You should also clean the oil coolers and heat exchangers. Replacing the radiator cap may do the trick as well.
• If there is still overheating, you can use a cheap point-and-shoot infrared thermometer to try to see where the highest temperatures are. You should see the temperature drop about 20°C from the top radiator hose to the bottom radiator hose. If the engine block is getting hot while the top hose remains cool, it indicates that either the thermostat is faulty (stuck closed), blocking coolant flow from the engine to the radiator, or the water pump is not circulating the coolant properly. To tell which one, you can take the thermostat out of its housing. This removes any potential blockage a stuck thermostat might be causing. You can then pour coolant into the thermostat housing, start the engine, and see if the fluid is circulating properly. If it does, then it’s most likely a problem with the thermostat; otherwise, it’s most likely a problem with the pump.

With great temperature comes great complexities! Along with decreased productivity, reliability, and efficiency, as well as increased downtime, costs, and safety risks. Having a maintenance schedule is non-negotiable, and so is replacing faulty or old coolant, filters, seals and more. Temperature control = happier operators, longer machine life, and better bottom lines. So remember, your Mini Digger is not training for a hot tub or sauna competition. Keep it cool, and it’ll do the heavy lifting for years to come.