Manufacturer of Hydraulic Presses
If you’ve been around hydraulic presses long enough, you’ve seen it happen.
The press starts the day running fine. By mid-shift, the oil’s hot. By the end of the day, seals are sweating, the press feels “lazy,” and someone’s asking if the pump is on its way out.
Most of the time, overheating isn’t caused by one big failure. It’s caused by a handful of small problems stacking up. The frustrating part is that many of those problems don’t look serious on their own.
Let’s talk about what actually causes hydraulic systems to overheat — and what usually fixes it without tearing the whole machine apart.
Every hydraulic system makes heat. That’s normal. If a press didn’t generate heat, it wouldn’t be doing any work.
The trouble starts when the system can’t get rid of that heat fast enough. Once oil temperatures creep past their comfort zone, everything else starts to go downhill: oil life, seals, hoses, valves, and eventually pumps.
In most shops, overheating shows up gradually, not all at once. That’s why it often gets ignored until it becomes expensive.
One of the most common causes of overheating is restriction in the system.
This usually comes from:
Each restriction creates pressure drop. Pressure drop equals heat.
A good rule of thumb: if one hose or valve is noticeably hotter than everything around it, there’s a restriction there. You don’t need fancy instruments to notice it — your hand will tell you pretty quickly.
Another classic issue is oil dumping across the relief valve more than it should.
This happens when:
Relief valves are not meant to be used as flow control devices. When oil constantly bypasses through them, it heats up fast. You’ll hear it too — that constant hiss or chatter is wasted energy turning into heat.
If a press spends a lot of time waiting between cycles, an unloading valve or a different pump setup can make a night-and-day difference.
Oil choice causes more overheating problems than most people want to admit.
Oil that’s too thick creates drag. Oil that’s too thin leaks internally. Either way, the system runs hotter than it should.
What trips people up is choosing oil based on what they’ve always used, not how the press actually runs today. Ambient temperature, duty cycle, and system pressure all matter.
If the oil smells burnt or turns dark quickly, that’s not “normal aging.” That’s oil being cooked.
Internal leakage doesn’t drip on the floor, so it often goes unnoticed.
Worn pumps, tired cylinder seals, and sloppy valve clearances allow oil to move without doing any work. That wasted flow turns directly into heat.
If oil temperature keeps climbing even when the press isn’t working hard, internal leakage is usually part of the picture. At that point, adding a bigger cooler just masks the problem.
Sometimes the system is doing exactly what it’s supposed to do — it just doesn’t have enough cooling.
This is common after:
Oil coolers get dirty. Fans fail. Water flow gets restricted. Any one of those reduces cooling efficiency more than people expect.
If the cooler is hot end-to-end but oil temperature stays high, it’s probably undersized for the current workload.
Overheating usually gives you plenty of warning:
Once oil regularly runs too hot, everything ages faster. That’s when maintenance costs start stacking up.
Start simple:
Don’t jump straight to adding a bigger cooler. Reduce heat at the source first. Many overheating problems disappear once restrictions are removed or pressure is set correctly.
Good oil, clean flow paths, proper unloading, and adequate cooling solve most cases without major redesign.
Hydraulic presses don’t usually overheat because they’re “bad machines.” They overheat because small issues get ignored until they add up.
Pay attention early, and overheating stays a maintenance task. Ignore it, and it turns into a rebuild.
Cool oil isn’t just nice to have — it’s a sign the whole system is doing its job.