Is the tiller hydraulic? Sounds to me like the hydraulic system is getting hot.

 

Chuck,

The tiller is the Snapper Model 48" Shaft driven tiller. One other thing I forgot to mention in my above post was right above this cylinder there are a few metal hydraulic lines I'd assume and at one fitting there is some leaking. it's leaking straight down under the fender past the trans. filter. For these hydraulic lines where is there a so called resivor ? Mabey the lines leaked out enough to loose power to the rear lift? and the lift itself is not bad ?

 

Ok,

I just went back out and started it back up ( sat for a hour and half) and the rear lift worked like brand new again. So when it get's too hot is when it get's so sluggish. Also re-looked at thoes lines right above the rear hyd. lift and they both go throu the frame and into the trans filter.

Then followed the one line the other way and it led right into the hyd. lever area, and then took a white cloth and wiped a little leaking fluid, so now I answered some questions. The lift levers/ cylinders run off the same trans fluid as the transmission/ and also obiously I know where to check / add trans fluid. So that answers that. and the trans dip stick shows the trans fluid is full.

So hopefully I can just tighten thoes nuts along the inside frame rail a little and stop the seepage. So that just leaves 1 question, Why does the line from the trans filter to the hyd. lever area get so warm and then make the 3 point lift function so poorly?

travis

 

Sounds like when the fluid gets hot it is leaking past the valve or cylinder. Could possibly be the pump. Does the trans work properly when the lift is working slow?

Geno

 

I'll bet the cylinder is bypassing.

 

I had a Massey 1650 do this very thing. Worked great cold, but the longer I used it, the slower/weaker it got. In my case, there was a blown o-ring between the body sections of the hydro pump/motor. 5 cent o-ring, a few hours work.

 

Also, if the cylinder is bypassing enough to cause poor lifting, the lift will go down with a load on it once you release the lift lever back to neutral. If it holds the tiller up after releasing to neutral, then the lift cylinder is not bypassing.

 

After more investigation after my last post I removed the plastic cover in the middle of the tractor where the shifter is for the " cruse control" and determined that the small seepage was comming from the metal line that goes from the trans. filter directally down to the top the the trans. housing. Without removing the whole rear fenders or having a certain length wrench I couldnt check very to to tighten that nut. From the little grip I had with a pliers it seemed plenty tight. So I'll just have to keep an eye on the trans. dip stick.

So that leads me to belive that that little trans. seepage has nothing to do with the weak rear hyd. lift as I orgionally thought. Also this evening the lift did go slower after a while but nothing like it was this afternoon.

relating to the cylinder by-passing when I lifted the tiller up to move around the tiller held the hight that I raised it to and I hadnt noticed it loosing pressure and getting lower to the ground.

Travis

 

Could possibly be the pump. Does the trans work properly when the lift is working slow?

Geno

 

There was no noticeable difference in the trans this afternoon, but then again I wasnt focusing on if there was or not. nothing obious anyways. I'll pay attention to it tommaro morning when I do some more tilling. see what happends.

thanks
travis

 

a couple things you might want to try, first if you are tilling till in lower gear, less stress on the hydro pump for the tranny. Second does your machine still have a fan cooling the tranny, if not you can try adding an oil cooler some where, or change out oil to a heavier grade oil. Is the oil reddish in color, if so that is an atf oil you can try a 30 weight oil if you need.Oh yes if the cylinder was bypassing it would not hold the weight of the tiller. It might creep to the ground if the 3 point has alot of wear but that is not hard to repair, change out some seals and rings.

 

If the line between the filter and tranny case is leaking,is that on the vacuum side of the pump , and if so could it draw enough air into the hydraulic system to cause a problem when he goes to lift the tiller at the end of the row.

 

My Massey 1855 deck used to do the same thing( settle down).I rebuilt the cylinder and the problem was gone.

 

When the oil gets too warm, it loses the ability to maintain pressure. The MF4850 tiller weighs over 300 lb and just about maxes out the 3PH. Add a little dirt to the tiller and a hot hydraulic system and the 3PH won't come up. I had a similar problem many years ago, and the root cause was damage to the differential causing the case to be chewed up and plugging the filter.

I currently have a similar problem with mine, even after rebuilding the cylinder. My suspicions run to the valve body as the culprit for my problem. I use the 3PH extensively with a backblade for snow removal and there is bound to be some wear in the aluminum valve body in 2500 hours of such use.

Address the leaks. A little judicious snugging up should fix them. If it's due for an oil change, possibly a heavier oil will help. I use Dexron in mine with the only issues being those mentioned above, even with extensive hard work in 80*+ temps. Definitely change the filter, even if it was recently changed, Take the filter apart and inspect for debris. If it's clear, you've eliminated the most expensive problem source and can move on to the time consuming seals and o-rings in the rest of the system.

The filter and valve are the most likely places for answers for the mechanical side and the filter and fan for the heat generation. Get an IR temperature gun and check the hydro the next time the problem happens. Normal is 140-160*, high, but acceptable, is 170-190*, over 200, add an oil cooler to the valve return line, and take a hard look for why the temp is getting up there. It shouldn't, except under extreme circumstances. Tilling a garden in 70* weather is not extreme.

I very much doubt that either a small drip at the suction line or the hydro itself is at fault.

 

Thank you for the education on the hydraulic system. I have more experience in the cylinder side than the pump side. If the cylinder is a 2 way it could still bypass when lifting and not creep down under it's own weight. If the seal is worn, the weight may not be enough to cause the tiller to drift down, but the pressure to lift may be enough to pass the seal.

Geno

 

I sorry bgkid2966 I am having a hard time believing that a cylinder will bypass under pump pressure but not drift under it's own weight. In my thinking if the pump is putting out lets say 750 psi and it takes all of that to lift the tiller, should there not be virtually the same pressure on that cylinder when the valve is off, less a little to over come momentum and friction. and if moving with with the tiller hanging off the back of the machine bouncing actually putting more pressure at times than the pump on the cylinder. I have been around heavy equipment and farm equipment all of my life and have never seen the situation that a cylinder will bypass. Now if the cylinder is worn more at one point in the barrel than the ends lets say it will creep faster in the middle of the stroke. I have seen earth movers that creep so bad under load you are virtually holding pump pressure on the lift while in transport. The owner of the equipment had the spools rechromed and solved the problem.

 

I sorry bgkid2966 I am having a hard time believing that a cylinder will bypass under pump pressure but not drift under it's own weight. .

According to the theory of hydraulics, that is exactly what is supposed to happen. Reality sometimes doesn't quite agree, due to extenuating circumstances.

In theory, if the valve and seals are operating at 100% efficiency, ie. when the valve is closed and absolutely no oil can get by it and no seals are leaking to the outside, then the piston will not drift down. There is a finite space within the cylinder and hoses which contains a fluid which has a very low compressibility factor. Within the cylinder is a piston with a rod attached which has a certain volume dependant on how far the piston is up the barrel of the cylinder. Assuming there is no sealing material on the piston and the oil can freely pass from one side to the other, how fast will the piston drift down when maximum load is placed on it?

Answer: It won't drift down more than enough to expand the hoses and cylinder to accommodate the pressure that the load creates.

Any drifting down will involve the cylinder rod taking up additional volume. Since the fluid is incompressible to all practical intents and purposes, and it has nowhere to go since it completely fills the available volume, there is no room for additional rod. It's locked hydrostatically.

I have a vertical splitter beside my garage. When I last disconnected it, the 20" rod was fully retracted. It is now extended about half way. The sole hydraulic source for that splitter has been down and parked elsewhere due to rusted out rims for the past 4 years. Why would the rod not be fully extended after that much time with the splitter knife attached? Because hydraulic fluid doesn't expand, either, except by the effect of temperature change. It sits in the sun every day and no seal is perfect.