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     One of the baddest machines a hydraulic technician may have to "battle" with is a hydraulic excavator. These multi-function mechanized monsters come in all sizes, forms and brands, and get more an more complicated every year, having become a real "troubleshooting nightmare" for anyone but those who have privileged access to detailed technical documentation, in most cases kept behind armored OEM's doors.

    This is the main reason why I stick to pumps, motors and standard component hydraulics. Every "protected" pump can be reverse-engineered in a workshop environment because you can strip it down to the smallest screw - something you can't afford doing with a twenty ton machine. When you deal with a modern hydraulic excavator, you deal with a very complex piece of hydraulic equipment, which still can be back-engineered, but the final cost and the time spent during the process doesn't justify it most of the times.

    "Most of the times", however, doesn't mean "all the times", and since a good half of the pumps and motors that pass through our workshop come from rotary excavators and excavator-based equipment, I occasionally happen to come in close contact with these noisy toys.

     When a hydraulic schematics is available (happens ve-e-ery rarely), troubleshooting becomes a relatively transparent process of logical elimination of probable malfunction causes. In such cases my main objective is to determine where the problem is and if I can repair it (I don't repair electronics and software related problems, for example). When a hydraulic diagram is not available, the troubleshooting process becomes a two-stage task. The first stage is "getting to know the equipment" and the second stage is the troubleshooting itself. The first stage is the most important one since you can not troubleshoot something you don't know. You must have a good understanding of how a hydraulic circuit works before elaborating any troubleshooting theory, otherwise you may end up doing something like this!

    This first stage is, therefore, ALL about back-engineering, and in case of mobile machinery it resumes to:

    a) hose pulling (to see what's connected to what) - an incredibly arduous, irritating and bewildering exercise due to the compact nature and most of the times remarkably shitty condition of them hoses, and

    b) component disassembly (to see what's inside and how it works) - another challenge due to the same above described reasons.

    Despite giving tons of trouble, this process can also bring you tons of true satisfaction when you finally confirm your theory and prove once again that knowledge of basic hydraulic component back-engineering strategies is an extremely valuable skill!

   The last time I "shined" (referring to my back-engineering know-how here)  was a couple of weeks ago, when a friend of ours from the Santa Maria (Azores islands, Portuguese archipelago in the middle of North Atlantic) asked if I could take a look at one "strange brand" excavator which had been immobilized for more than a year.

     Azores archipelago is one of the most gorgeous places on the Earth, and I had the privilege of visiting this beautiful destination many times (thank you very much, hydraulics), so I was well aware of the fact that, while on the main island (Sao Miguel) hydraulic supplies were relatively easy to obtain, more distant small islands (like the Santa Maria) were industrial-desert-like places, lacking everything, even the simplest stuff like fittings and gauges, so I grabbed all the gear my weight limit allowed (plus a couple of extra pounds in the back-pack) and caught the first flight to the Sta Maria.

    Flying with hydraulic equipment test gear is one matter that deserves to be described separately. I confess that I've become used to opening my luggage and describing to armed officers that what I'm carrying isn't a bomb, but a digital pressure gauge, valve, flow-meter, part, etc... With the biggest confusion being caused by the fact that in Portuguese language the word "pump" and the word "bomb" are the same word (honest!), so even when I bring along pump parts, I never ever say that these are pump parts (bomb parts!) and humbly call them "motor parts", making everybody happy...

    Anyhow, the machine in question was a small wheeled Furukawa (a rare name in Portugal), which apparently was not moving due to the insufficient joystick pilot pressure. No need to say that no hydraulic schematics was available. Sheer amount of hose pulling and a couple of pressure readings narrowed the malfunction down to this manifold, which held various unknown valves, and had multiple connections. Since I had no information on what was inside the manifold, but was sure that it was supposed to supply the joystick pilot pressure, I decided to dismount it from the machine and do the one thing I liked doing the most with unknown hydraulics - reverse-engineering.

    For a couple of hours curious standers-by watched me blow through the manifold openings with an air gun (sprinkling all around me with oil mist, myself included), shove wires in holes, inspect them with a flashlight, disassemble all of the valves to small pieces and make some strange doodles on a piece of paper. I bet the thought "the guy's gone koo-koo" passed through more than one head that day... But in the end I knew exactly what the manifold valves did, and with certainty narrowed the malfunction down to one single pressure reducing valve. On a closer inspection it turned out that the valve stopped functioning properly due to appearance of wear groove on the small ball in the pilot section - the groove was so deep that the ball couldn't seat properly, resulting in oil leak and the consequent low pilot pressure. The ball was replaced, the manifold re-assembled and re-mounted, and - Alleluia! - the machine moved, for the first time in more than a year!

     It was an enormous satisfaction to witness yet another evidence that all that time I spent back-engineering hydraulic stuff and studying designs paid off!

    Note, please, that this article should be considered as me praising reverse-engineering and not me bragging about my troubleshooting talents.


    P.S.  People often ask my opinion on which hydraulic equipment to buy. I always answer - buy the one that comes with a hydraulic diagram!