Mazak CNC lathe leaking

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Here is an episode that I faced with an old Mazak CNC lathe. Now Mazak CNC lathes are pretty good machines in my opinion, even the old ones. What I am about to discuss in this post is regarding a problem I faced with an old Mazak CNC lathe concerning leaking hydraulic oil. I am sure those of you that have dealt with older models of cnc lathes have had the problem of leaking hydraulic oil at one time or another caused by leaking o-rings, seals and such. But this was a problem that bothered me so much for so long a time that I was almost ready to give up even though giving up is something I do not cherish doing.

In all honesty, the subject Mazak cnc lathe that I am talking about was purchased brand new at our shop over twelve years ago. Fitted with an SMW bar feeder, this machine made parts relentlessly every day of the week, seven days a week about fifteen hours each day. And so I cannot really complain too much. Over the course of this hectic production schedule, we did have leaking hydraulic oil problem every once in a while and almost every time it was a hydraulic hose that formed a pin hole and simply replacing the hydraulic hose would solve the problem. But no, not this time.

This time around the hydraulic hoses were all in good shape and yet every week, the floor around the Mazak cnc lathe would be wet with oil. We were so busy that we would simply clean up the oil and go on because we simply could not find the leak source. Finally, this morning, a different problem arose that led to the source of the problem. The problem that arose this morning was a “low hydraulic pressure alarm” and the machine would shut down. I checked the pressure gage on the hydraulic pump and the hydraulic pressure was fine. I said to myself, this machine is over a dozen years old and so may be the pressure sensor has failed. So, I reached the pressure sensor which was mounted in an awkward position in the back of the hydraulic pump with two wires that lead out of it and the wires were covered by a piece of rubber. I pulled the rubber and found oil in the rubber cap which should not be there. Then the two wires were jumpered, so I eliminated the pressure sensor reading and the machine started working fine. So I determined that sometime soon we will install a new pressure sensor.

But as soon as the machine was restarted, I saw oil level in the hydraulic tank go down again and upon inspection, it was leaking from the pressure sensor which was still connected, only electrically disabled. Since the pressure sensor was openly visible now, with no rubber caps covering it, I could see there was a little screw in the center that had come loose. I tightened it and there the problem got resolved. Sometimes it takes a second problem to arise to diagnose and fix the first problem, I thought to myself in a chuckle!