MM 670 Hydraulic problem

[shoptek]

I have a MM 670 Super tractor that the hydraulics have started acting up on. When I raise or tilt the bucket (it has a loader on it) the hydraulics jerk and sometimes stop. I changed the filter and the oil is full. It acts like it has air in the line but it doesn"t that I know of. I put a pressure gauge on it and it will produce 1400# pressure so it will pump pressure. It also has lift capacity as it will lift a full bucket of snow if it wants to. It will also raise the front end off the ground with down pressure. It just acts like the pump is not getting oil. Anybody have these old gear pumps apart or what should I look for.TIA

 

[Leyland-270]

I have a million questions about your set up but I am going to guess that you have a valving problem. Most likely a bypass or priority.

Does your loader have its own valves or does it use the tractor's valves?

 

[BCnT]

i had a similar problem with my dozer...check suction line for leaks or a stopped up screen in tank.

 

[JMS/.MN]

If it uses a suction hose, it may be collapsed internally.

 

[shoptek]

It has original tractor valves and it was acting up before I changed the filter, that"s why I changed it.Also when I had the filter off about 1 gallon of oil ran out of the filter housing fairly fast when I had the filter off. Both valves work the same so it can"t be in just one of the valves. I don"t have any books on this hydraulic so I don"t know where to start. If there is a suction screen on this where would it be.I doubt it would have a screen in it as the pump pulls from the filter, so all the oil has to come thru the filter before going to the pump. My other thought would be the possibility of my landlord adding the wrong kind of oil in it and possibly getting some foaming???? I had a leaking line on the pressure side under the platform and was loosing some oil. The landlord has been using the tractor and he said he had been adding oil to it.I question whether he was adding Hytran oil or maybe something else,who knows maybe he was adding some other oil as I had no Hytran oil up there and I doubt that he bought any.... One other thought would be there is a short hose that cuoples the large suction line together. It is only about 4" long and is original,is it possible that it could have colapsed. I doubt it but looking for the easy stuff first.