Hyd oil suction screen is accessed by removing cover(item 21)
Thank you, Jim. Yes, the suction strainer is number 24 - the tubular looking thing with a couple of splotches on it. It's actually a rolled up piece of of metal screen about 8" long and an inch or two in diameter - about the size of a empty paper towel roll. It isn't screwed in, the strainer simply pulls out endwise once the hose is cover is taken off.
The O ring and packing can usually be reused. They are for locating the strainer and holding it in place rather than sealing it. The strainer itself can be cleaned with a soft brush and soapy water.
The function of the strainer down there in the bottom of the oil sump is to strain the larger pieces of crud out before they can get sucked up into the oil pump and distributed everywhere. It was a good idea, but given a few decades and the inevitable water condensation you get in transmission/hydraulic oil, the strainers do tend to plug up and stop the flow of oil to the pump. The JD 755 uses pressurized oil for to turn the hydraulic motors that drive the tractor and also for all other hydraulic functions - so when that strainer clogs nothing works.
It may not be your problem - or not all of it - but we have to do this as a first step. Also look around or ask JD if there is another external "spin-on" type filter for the hydraulics that is not cleanable but must be replaced. Not the engine oil filter. But it is a similar looking cannister. If it has one, replace it at the same time.
Like I said, this may not be the problem. But it is the most common single problem with these Yanmar-derived tractors and a necessary first step regardless.
When you remove the cover 21, first remove the drain plug in the end of the cover and hopefully expect about FIVE GALLONS of oil to come gushing out. So be prepared. If the oil is clean it can be filtered and reused, but it is so much better to just replace it. It needs replacing every decade or so anyway because it gets condensation in it. John Deere will probably want you to put in HyGard Trans/Hydraulic oil. Their regualr viscosity or winter Low Viscosity type - either is OK. Be sure to be holding onto something sturdy when they tell you the price of that oil.... $30/gallon is typical....although you can get it on Amazon
Now when you put the strainer back in and the cover #21 back on look carefully at that pipe that fits on the cover. It is called a "suction pipe" because it uses suction to pull the oil up to the oil pump which is probably mounted on the right side of the engine.. And that brings us to the second common problem with these tractors. Because there are half a dozen pipes and rubber flanges and hose clamps involved in getting that oil up to the oil pump. And if any one of these joints has the smallest air leak - even the size of a sewing needle sized leak - then the system just cannot build enough suction to get oil to the hydraulic pump and although the motor runs, eveything stops working.
Those suction leaks can be very hard to find. Suction leaks are always a hair puller. It's not uncommon with old hoses to find htat they have a microscopic crack at the end parallel to the hose through a old split on the INSIDE face of that old hose where all you will see is pretty much nothing... It happens with older rubber hoses where the hoses slip over a metal fitting and are tightened with a hose clamp. Once you get an old hose slid off of the metal flange you can peer in and see what I mean. When it is installed, all you can see is the end of the hose.
BUT THERE IS A TRICK to find out if that is leaking! Although a leak can suck air when the engine is running - and then nothing works - when the engine is NOT running is when the oil can slowly ooze out of a leaky hose end. It can leak out because suction is no longer keeping it in the hose. So if you see one of those hoses that has an end that is suspiciously wet with oil - and maybe even slowly dripping when not running - best replace that hose completely.
Oh, don't forget to drain and save your new oil if you do.
But for now, the first steps are simpler: just clean the strainer, look for a spin-on filter & replace it if you have one, get some new oil, and when you put it all back together keep an eye open for old leaky hose connections.
Best of luck,
rScotty
