Basic questions from new owner

[N1ST]

Hi All,

I was reading in another thread that the safety relief on the FEL control will allow fluid to be released when the bucket or arms are at their full reach or when lifiting too much. Since I often hit the full reach of bucket or arm (for a second or 2), is that to say that some fluid is frequently being released by the safety valve?

After using my FEL for a few hours last time, the input and output connectors on the back of the FEL control were a little wet and there were a few drops on the floor mat just below. Is this a normal result of the safety relief? I was initially thinking they might be loose.

I was lifiting some pretty heavy log pieces with the FEL and did hear a little whining. Is this OK or am I causing damage? The control also got quite sticky in the left and bottom positions after a couple hours of hard use. Sticky to the point where at times it did not return to center. The stickyness hung around even several hours after the tractor had cooled down, but was gone the next day. What could be the cause of this?

Tractor is MF GC2310.

Thanks.

 

[Farmerford]

N1ST:

It is expected that the pressure relief valve on loaders will often be activated, and in general it does no damage. When the valve opens it means the pressure in the system has built to the maximum intended by the designer; therefore the components are under their maximum loads and generally they will wear more than under light loads, but that is just normal.

Fluid flowing through the pressure relief valve does generate heat because the energy inherent in, say, 3 gallons per minute of fluid at 2500psi, has to be dissipated in some manner, and since it is not lifting the bucket, etc., it is converted into heat which raises the oil temperature. But that is not harmful in normal amounts. Exact termpeature maximums vary with the manufacturer, but 180 deg F is one of the lower maximums one sees. Oil at that temperature will quickly burn the skin, so as long as your valve does not get too hot to touch you are okay.

Indeed, the owner's manual for my Caterpillar dozer recommends that you warm the hydraulic fluid to conduct a pressure test by holding the dozer blade valve against the stops so that all the fluid flows through the relief valve "for several minutes".

The outflow from a pressure relief valve stays in the system, so the drops of oil you see are caused by something else; probably a loose fitting around the quick disconnects. I have purchased several loaders over the years and, it may just be my luck, but every one had at least one loose fitting on the valve. Or it is possible that the quick disconnects are leaking. They normally weep just a bit, but drops of oil are more than I would expect from the quick disconnects.

Your sticking valve may be termperature related. Most FEL valves depend on the tight fit of the steel spool inside a bore in the cast iron valve body to seal the hydraulic fluid. Steel has a significantly higher coefficient of linear expansion than cast iron, so as temperatures rise the spool diameter grows larger faster than the bore in the valve body. If the initial fit was very close, I suppose a temperature rise from normal to say 150 deg F could eliminate the clearances entirely and make the spool bind in the valve bore. I have never experienced that personally, but it is certainly theoretically possible. The only thing that doesn't fit that diagnosis is that the stickiness continues after the tractor has long cooled down. Next time check the temperature of the valve with your hand as it warms up and as it cools down to see if you can find a correlation.

The other fact that is not consistent with my guess is that the stickiness is only in the left and down positions. That is, when the loader is being raised or the bucket curled. I would expect the spool to bind in both directions, but I suppose it could be binding only in one place.

Fine particles (silt) in the fluid can build up in the crevices of a valve and make it stick, but that normally does not cure itself like your problem. You could also have defective return springs in the valve that were marginal when at normal temperature, but that lost enough force when heated that they would not return the spool, but that seems very unlikely.

In any event, I don't think the sticky spools are hurting anything, and if they are sticking due to expansion they may loosen up after a lot of use.

 

[RonMar]

The fluid always must flow!, If you try to lift the loader with too much in it, and you move the lever control and the loader dosn't move, the fluid is still flowing, just at high pressure(set system pressure) thru the relief valve. It is called a safety relief, but it is probably better to think of it as a system pressure regulator as it maintains the pressure at a safe working level for the plumbing and structure. It is perfectly normal for fluid to flow thru it when the load is too great or the cylinder extension/retraction reaches it's limit. Pressure causes heat. leaving a lever held over unnecessarilly when the loader isn't moving will add unnecessary heat to the oil.

I have yet to see a hydraulic system that dosn't leak. Had a crew chief on a CH-47 chinook(all hydraulic control system) tell me one time that when you stop seeing it drip, be affraid because it is out of fluid. Can you determine where exactly it is comming from? It could be leaking past the threads on a fitting(loose or if NPT, perhaps requires sealant). It could be leaking past an "O" ring on a spool. The spool slides past these rings and carries dust/dirt in against the ring and causes wear which will eventually cause it to start leaking. No big deal, "O" rings are cheap. These typically seal the return(low pressure) gallery. IF there is excessive restriction on the return line(clogged filter), this could be forcing fluid past the rings.

As for the linkage sticking, this could be a few things. It sounded like you described a joystick. It could be as the valve body warmed up, the linkage is binding in some fashion. The spools could be expanding at a little different rate than the body causing extra drag. How old is this machine(how many hours)? If it is new, it probably has never run at that temp before and might take a little breaking in for things to loosen up at temp. It could be a combination of thermal factors and debris in the fluid making the spool harder to move. When I say debris, I am refering to dirt and metal shavings from the machining processes during the fabrication of the pump, valve or resovoir. It is very difficult to get all of it out. The spools are a close tollerance fit in the valve body so it dosn't take a very large piece of debris to impede their movement. Are the spring end caps on the spools tight? If they become loose, you might loose spring force to return the spool to center by itself.

 

[N1ST]

Thanks for the replies - you guys are terrific and obviously very knowlegable. Thanks for the explanation about the relief valve emptying back into the system.

I can't anwer all of your questions Ron because of my limited knowledge, but i will tell you that the machine is new - only a few hours on it. so perhaps more time on it will reduce the stickyness as the parts wear together. However, even when cold and off, the tension when moving the FEL joystick right and up seems more than down and left. Could this be just an issue with weak springs, or are different pieces in play when moving say left vs. right?

I can't say exactly where the tiny amount of fluid was coming from, but the hose connectors that were wet were not the quick disconnects on top. They were the source and return on the back of the controller (and not the power behind on the side).

Please tell me how to check the tightness of the input and output connectors. There's a molded nut on the very end and another nut just behind this. What is the sequence for tightening? How much force should I use... should they be just snug or very tight? Is this OK for a novice to attempt?

 

[Farmerford]

N1ST:

Down and up on the joystick move one spool and left and right move the other spool. Seems like the stickyness is down and left when hot and up and right when cool. I am not sure why that would be unless the valve body is warping when it heats up. I would just live with that for a while to see if it improves. If it doesn't, disassemble the valve and clean it (or get a hydraulic shop to do it).

There are three (actually dozens) types of hydraulic fittings that could be on your valve. Tapered pipe fittings do not have to be very tight if properly sealed with paste sealant (or teflon tape for the uneducated like me); certainly not as tight as you can tighten them with a wrench. JIC flare fittings also do not require much tightening in most cases: again, snug, but nothing like as tight as you can get them. O-ring boss fittings do require firm tightening to properly compress the o-ring into the boss. In some cases you turn the o-ring boss fitting itself, but in most cases you tighten the adjusting nut which in turn forces the o-ring into the boss.

My practice for pipe and JIC fittings, if the fittings are easily accessible in the future, is to tighten them barley snug and the retighten the ones that leak. The reason for that is that overtightening can permanently distort the fitting so that it cannot be reused after it is loosened in the future.

I know you don't want to get a new tractor oily and dirty, but after a while it will not matter and you will appreciate how the oil prevents rust.

For most loaders, the pump/pressure in port and tank/reservoir out port are the hardest to get to after the valve is mounted, and proper tightening can be difficult. I would snug them up one at time just a little bit to see if the leak stops. If you send us a picture you we may have more specific hints.

 

[Farmerford]

N1ST:

I forgot to mention that there are tightening specifications in terms of "turns from hand tight" for pipe and "flats (on the hex nut) from finger tight" for JIC that you can easily find on the net if you want to be very precise. But these normally apply to the first tightening because that is when the components conform to each other. Then, you mark the relative positions of the parts of the fitting and when you retighten you do so to the same place as the original fitting (and just a tiny bit more for disbelievers like me).

 

[RonMar]

The binding could be the joystick linkage or just being new. The linkage is probably covered with a rubber boot at the base of the joystick. Got any pictures of your machine?

Lots of different type fittings out there, Farmerford certainly hit the highlights and cautions. Good practice when working on any hydraulic fittings is to make sure the loader is down solid and all pressure is relieved by cycling the joystick to all positions. As mentioned, snug should be good, but too tight can cause distortions in the mating surfaces of some type connectors. Again, pics of what exactly you have for fittings might lead to some more specific suggestions.

Don't be afraid to take a wrench to your new tractor. In fact it is a good practice at greasing or oil change time to crawl all over it with the appropriate wrenches and sockets and make sure things are still tight. It beats **** out of stumbling around in the field looking for the part that fell off, or working on it out in the field when it quits running cause a water or oil fitting came loose. Or calling in another tractor for a tow or a crane to lift her back up when a wheel falls off. Sounds silly, but yes it does happen.

 

[motepoc]

I am new to this and this is my first reply to any post, but since the equipment is new, why not have the dealer take care of the leaks for you.

 

[N1ST]

Farmerford - there's no stickyness in the up or right position, just in the left and down (and only once so far). I used it last night for about a half hour, and didn't experience any sticking, so it might have to get real warmed up.

I'll try to get a pic of the controler over the weekend.

Yes I could take it to dealer, but there's the hastle involved of transporting, perhaps being without it for a few days, etc. At this point I'm certainly not alarmed by the tiny leak, and I'd like to give it some time to wear in to see if it goes away. Besides, I'm learning a great deal from the answers to the questions.

Thanks.

 

[KJM]

N1ST - cheap leak finder is baby powder (talc - not ground babies ). Clean everything (with whatever) then dust liberally and use. The talc absorbs the oil and you very quickly see where it is coming from. Dust works too, but is likely to be somewhat abrasive and looks significantly less "scientific"..

I just fitted a new Brand Hydraulics joystick valve to my little kubota. It had exactly the same stickyness you described. In my case it was just the linkage mechanism under the rubber boot. A squirt of lube was the 100% cure, but which little joint was actually sticking I couldn't determine - so I just lubed them all!

Cheers
/Kevin