Hydraulics not working - only a buzzing sound

big derek · Aug 27, 2007

Hi there:

I have a Mitsubishi Shatoh S630D-Bull that is around a 1982 model. It is used regularly for just cutting grass and grading dirt and some occasional lifting. The hydraulic bars in the rear stopped working to lift the rear mower/grader box. All I get is a "buzzing type" sound. The tractor's hydraulics always made this buzzing sound ever since it was new, but only when I tried to raise the hydraulic bars too high - now I get the buzzing sound and the hydraulics bars don't move at all. I changed the hydraulic fluid and the cleaned the filter, but to no avail. I'm not sure if the hydraulic pump is bad or even how to test it, but I have a feeling that maybe the hydraulic lever is bad or needs adjusting. Any troubleshooting or advice is greatly appreciated. Thanks. Derek

RonMar · Aug 27, 2007

Well that "buzzing" sound might be a safety relieving pressure. Usually the first stage in any hydraulic troubleshooting is measuring the pressure out of the pump. Unfortunatly most systems are not plummed for this so some plumbing is usually involved with "T"ing a high pressure gauge into the high pressure supply line comming out of the pump. It dosn't sound as if you have a loader attached. A quick way to check pressure availability is to screw a gauge into the loader valve port in place of one of the lines going to a lift arm or bucket cylinders, then sending pressure to that port. The pressure test is good as the pressure performs the work. If you have the pressure and no work, then the problem lies in the valve or cylinder.

It could be the safety on the 3PH control valve has failed or the adjustment has worked itself loose. In my experience these are usually fixed types with a spring under a screw in plug holding a valve seat in place to contain the pressure. When system pressure overcomes the spring, the seat lifts and vents fluid. Since you didn't describe the symptom of the 3PH lowering by itself with a load on, I don't think the seals in the cylinder are the problem as they usually leak before they completely fail. You may also have more than one safety on the 3PH. One on the valve to protect the pump and another internal to vent and protect the cylinder and structure if you should bounce a heavy impliment and it pulls some "G"s

Do you have any pictures of the control valve? A couple close shots of all sides so we can see all the fittings and ports might give us some ideas of where we can tell you to look next. The fact that it is making noise when you move the lever means something is flowing though but without a pressure test, you could be looking at a good valve for no reason.

big derek · Aug 27, 2007

Thanks for all the good information Ron. I will take some pictures at close up angles this weekend for you when I get back in town. Thanks so much for the help. Derek

big derek · Sep 2, 2007

Hi Ron:

I took 13 close up-pictures from mutiple angles of the tractor showing the various angles of the hydraulics system. I hope these will assist you in helping me trouble-shoot the problem, but TractorByNet only only allows you to upload pictures that are less than 1 MB. If I compress each picture to that size, most of the clarity is lost. Would it be okay to send these pitctures to your outside E-mail, if so please give me the address? I know most servers such as Hotmail and Yahoo will allow up to 10MB. If not, I will get with my IT Department and see if they can help me compress the picture into an electroic format that is less that 1 MB. Thanks so much for all your time and help. Derek