Go BottomHydraulic Stop Valve
 | Bruce W.
Join Date: Posts: 1 
|
2001-08-24 31258
Can anyone help me figure out what the hydraulic stop valve is used for? When does it need to be fully open or fully closed? I've got a JD MX-5 brush cutter and a front loader on the tractor. I ran the brush cutter for the first time the other day and my hydraulic hoses to the loader valves became very hot. I can't move the stop valve, "rusted"?, but have applied something to unfreeze it. Any help would be appreciated. Thanks.
Reply to |
Quote Reply |
Add PhotoHydraulic Stop Valve
 | Murf
Join Date: Dec 1999 Posts: 7249 Toronto Area, Ontario, Canada 
 Pics
|
2001-08-24 31259
Bruce, I can only assume from your description that by "stop valve" you mean the screw valve which adjusts (or stops) hydraulic flow to the 3pth. If this is what you mean, it is there so that you can adjust (usually because of varying weights) the speed at which implements mounted on the 3pth actually drop at, irregardless of the speed that the control is moved. This way heavy objects, like your brush-cutter, don't slam inot the ground if you move the lever to fast. These valves do tend to get a little stiff if not used regularly (and not many do), gently move it back and forth, it will loosen up, but don't use more than firm pressure, if you break the stem off you will be really .... annoyed. As for the temperature of the hydraulic lines, don't worry, it is normal for the lines to get hot to the point you don't want to hold them for long, this is just the fluid doing it's job, keeping your transmission, differential and pto cool, and lubricated. Best of luck. ....
Reply to |
Quote Reply |
Add PhotoHydraulic Stop Valve
| Bruce W.
Join Date: Posts: 1
|
2001-08-24 31264
Thanks for the info. I'll make sure to try a free it up gently. I am wondering about the rate of drop issue. My tractor is a JD 950 and it has another small valve with a lever handle, located under the seat. The manual says is used to control the rate of drop. I've been able to work this one free, but have not tested the rate of drop yet. The manual says that if you turn the lever towards the front of the tractor, then the rate of drop will be slower. I've also heard that the stop valve can be used to heat up the hydraulic fluid when its cold out by closing it for a short time and forcing the fluid past the relief valve. ....
Reply to |
Quote Reply |
Add PhotoHydraulic Stop Valve
| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
|
2001-08-25 31270
The difference between normally hot and over-heated is a little tough to call over the net. Murf probably is correct, but I would keep in mind that an obstructed or overworked hydraulic system can over-heat the oil which can damage things. If the hydraulics seem to have low power or speed, I'd listen to see if the relief valve is open or if the hydraulic pump buzzes or rattles. If the oil heats when using the rotary cutter but not the loader, there's a chance the cutter is large for the tractor and the flow-control valve is fairly closed down. In that case, the hydraulics would be heavily worked and the oil would heat.
I haven't heard the term 'stop valve' before. Since there seems to be another valve identified as the flow-control valve, I wonder if the stop valve is what I call a diverter valve. On many tractors, a diverter valve selects between remote (3ph) and auxiliary hydraulic systems. The auxiliary system provides a external feed and the auxiliary return flow usually feeds back into the high-pressure line to the 3ph. A tractor with a loader usually runs in the auxiliary system position. With the valve in 'remote' the 3ph should work but the loader wouldn't. I guess if the valve wasn't fully in either position it could create a line obstruction. Pressure ahead of the valve could be abnormally high and the oil could be abnormally hot. If that is the case, both the loader and 3ph should be slow and lines should heat when either the loader or 3ph is worked. I suppose that somebody who knows the tractor should comment so the valve can definitely be identified. If it's a diverter valve, it would be good if it worked freely and was fully in the aux position.
....
Reply to |
Quote Reply |
Add PhotoHydraulic Stop Valve
| Sparky
Join Date: Jun 2004 Posts: 0 Florida
|
2001-08-25 31271
On JD 4000 series the knob is called Speed of Drop/Lock Valve. Does anyone know
if hydraulic pressure is reduced to a backhoe, or any attachment that takes hydraulic pressure, depnding on how far the valve is to closed or even closed all the way? Also if lift arms? ( rockshaft ) is raised all the way and valve locked, does that hinder hydraulic pressure or damage any inner workings while running backhoe ? The person who dropped off my tractor and backhoe demonstrated how to attach the backhoe. He raised the backhoe with the rockshaft, pinned it in place and kept the rockshaft raised to hold it there. I ran it an hour then eventually read the instructions. You are told to lower the rockshaft and let the backhoe rest on the pins you installed earlier! Not hold it up with the hydraulics locked in place! Also, is it normal for a backhoe to drop in about a day till the bucket touches the ground? ....
Reply to |
Quote Reply |
Add PhotoHydraulic Stop Valve
| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
|
2001-08-26 31298
The flow control valve affects only the drop speed of the 3ph. The power of the 3ph and other hydraulics are not affected. It sounds like there may be some 3ph leak down, which isn't a serious problem at moderate levels. From the comment, I hope the hoe is a sub-frame mount where the 3ph is used to lift the hoe onto the sub-frame mounts. If it's a 3ph mount, the comment may indicate a very serious problem. I believe that all 3ph hoe mounting systems all lock the 3ph down. If the 3ph doesn't lock down, the 3ph could accidentally be bumped into lift mode when an operator is in the hoe seat. The result is that the operator gets mashed between the hoe console and the ROPS. It doesn't hurt a 3ph to hold weight during operation, but weight ordinarily is taken off everything when the tractor isn't used. If the hoe rests on the pins, then weight is off the 3ph. I don't understand why the hoe would leak down to the ground over-night when mounted unless the mounting pins were removed, and I don’t why they would be removed. Maybe it's not an issue, but I don't believe I'd want my 3ph subject to a lot of jolts if it were locked at the top of its travel. However, it's probably safe to trust engineering design as long as the mount is properly installed and adjusted. I would make sure that the 3ph is properly adjusted so it goes out of lift mode before the top of travel is reached. A 3ph shouldn't continue to lift when at the top of travel. ....
Reply to |
Quote Reply |
Add PhotoHydraulic Stop Valve
| Sparky
Join Date: Jun 2004 Posts: 0 Florida
|
2001-08-26 31302
Thanks for the info. JD 4400 has a frame mount, not 3ph mount for backhoe. The 3ph is used to simply lift it onto the plate steel mounts bolted to the tractor, then lower the weight of the hoe onto the 1" pins you slide in when all is lined up. Once you figure it out it is fairly quick to install, really fast to remove. So you don't think I damaged the 3ph by working the hoe with the weight hanging on it instead of the pins? ....
Reply to |
Quote Reply |
Add PhotoHydraulic Stop Valve
| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
|
2001-08-27 31312
Probably no damage, but sticking with a manual's instructions always is a good idea. I imagine the pins are designed to take the working load. There's no need applying load shocks to the 3ph if you've got a hoe mount designed to avoid doing that. I think that the geometry of a 3ph hoe places most load shocks on the top-link. Load on the lower-links would come mostly from lifting, and would be down rather than up. I don't think it's too likely that the lower-links of your 3ph would be forced up. However, there is an absolute mechanical limitation to the upward travel of a 3ph. I believe it's possible to break a hitch by backing an implement into something with the hitch full up. ....
Reply to |
Quote Reply |
Add PhotoHydraulic Stop Valve
| Bruce W.
Join Date: Posts: 1
|
2001-08-27 31323
Tom, what you are saying seems to match what my tractor has. I still have not been able to free up the stop/diverter valve. One other thing that has started to happen since I hooked up my new bush hog and began running it is a hydraulic fluid leak. I traced it to a small hole located on the front of my bucket level control valve cylinders. The hole is centered on a cap held in place by four allen bolts. Any idea what this is? A relief valve? Why it may be leaking? ....
Reply to |
Quote Reply |
Add PhotoHydraulic Stop Valve
| Bruce W.
Join Date: Posts: 1
|
2001-08-27 31324
Tom, what you are saying seems to match what my tractor has. I still have not been able to free up the stop/diverter valve. One other thing that has started to happen since I hooked up my new bush hog and began running it is a hydraulic fluid leak. I traced it to a small hole located on the front of my bucket level control valve cylinders. The hole is centered on a cap held in place by four allen bolts. Any idea what this is? A relief valve? Why it may be leaking? ....
Reply to |
Quote Reply |
Add PhotoHydraulic Stop Valve
| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
|
2001-08-28 31347
There are various o-rings in a loader control valve assembly. Sounds like one is leaking. Most of my practical wrenching was done on trucks and motorcycles. My tractor keeps on going and doesn't afford me much practice, so I'm mostly theory here. I don't believe rebuilding valve assemblies is too difficult, but there are contributors here who have taken apart bunches of these things. It helps to have a repair manual before starting a tear down, but a tractor manual probably wouldn't cover the loader valve. If it's a minor leak, I'd just ignore it and top-up the fluid until aggravation motivates a repair. However, a manual would cover the stuck diverter valve, which is something that probably should attended to. The stuck valve and leak might be parts of the same problem. An eventual repair is likely though, because once an o-ring starts leaking it doesn't usually stop. I'm curious if the loader valve is a power beyond valve. A power beyond valve can be identified because it has one hose to the inlet section and two from the outlet section whereas a normal valve has only two hoses. A valve without power beyond used to feed the 3ph can place abnormal pressure on the loader valve. This can occur if a loader operation is attempted at the same time the 3ph is in lift mode with a heavy load. Such a condition could produce a leak or worse in the loader valve. ....
Reply to |
Quote Reply |
Add PhotoHydraulic Stop Valve
| Renee
Join Date: Posts: 1
|
2001-09-21 31925
It is not unusual for the backhoe to drop over a period of time. The 4000-series tractors have an open-center hydraulic system that is not designed to hold a load in the up position for long periods of time with the engine not running. If you leave your loader in the up position, you will notice that it also drops over a period of time. (This according to the Tom Bowen at Ag-Power, Terrell, Texas, the salesman who sold us our tractor). We don't have a backhoe, but he said the result would be the same with a rotary cutter or any other implement of significant weight. The drop will be less noticeable on lighter implements, such as a box blade. ....
Reply to |
Quote Reply |
Add PhotoHydraulic Stop Valve
| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
|
2001-09-25 32000
Yep, I sort of snookered myself once. I parked the tractor with the loader bucket over a box scraper. Over several weeks the bucket settled down over the scraper, and I couldn't move either the tractor or the scraper until I started the tractor. If the tractor had not started, I would have had to float the bucket in and jack it up by hand so I could tow the tractor out of the shed. But it didn't happen and I guess this is just an illustration. Implements do leak down on both open and closed systems. However, in a normally working system, it's a matter of weeks rather than hours. I left the loader up for a particular reason, but it's a real good idea to set everything on the ground whenever the tractor is shutdown. Setting things down means the seals don't have to hold pressure over prolonged periods, and it's also a safety thing. Hoses rupture, kids play on tractors etc. Buckets and implements can drop like rocks. Or in my case, a more likely problem is that I'll forget something is off the ground and disconnect a hydraulic hose. Then, the lines have pressure in them, and reconnecting the quick-connects isn't so quick. ....
Reply to |
Quote Reply |
Add PhotoHydraulic Stop Valve
| Randy
Join Date: Feb 2002 Posts: 76 myLocation
|
2001-09-25 32021
All this talk of 3PH and diverter valves brought back to mind a situation I was asked to fix on a JD 750 2WD tractor with FEL quite a few years ago. A summer camp not far from me bought the tractor new, when it was just over two years old some one was using the grooming mower when all of a sudden the tractor bogged down and then quit.
When they tried to start it there was a terrible sound coming from the side of the engine and there was no hydraulic's at all, 3PH or FEL. I removed the hydraulic pump and found the drive gear shaft sheared off and the gears milled into the housing. I installed a new pump and housing.
However, I did not have a clue why this happened or how it could be prevented from happening again, so I called JD tech. service. As best as I can remember they figured it had soemthing to do with a valve under the seat being closed which stopped the flow of hyd. fluid. When this happened the pump pressure built up with no place to go and the pump broke.
There was some reason the pressure relief valve was cut out of the circuit when this happened, I wish I could remember all the details it's been over 12 years. The tractor is still running today without any more problems with the hydraulic system. Maybe someone else can shed some light on the subject, but it seems that closing those valves all the way could lead to a bad condition.
Randy ....
Reply to |
Quote Reply |
Add PhotoHydraulic Stop Valve
| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
|
2001-09-26 32022
Randy: I’d guess that the system relief valve was in the system, but perhaps failed. At least the relief valve on my Ford 1710 is always in the system irrespective of the diverter valve position. However, I believe that prolonged operation with an open relief valve open could over-heat the oil and cause a pump failure. It does sound like the pump or drive seized.
Some JD's have the diverter valve under the seat, although I tend to think of the flow control valve when I hear 'under the seat.' A diverter in the auxiliary system position with nothing connected to the auxiliary system is going to ‘dead-end’ the pump, except for the power steering through a priority valve on some tractors. The relief valve should open, but prolonged operation would over-heat the oil.
I don't think the flow control valve is the answer. My understanding of a 3ph is that the flow-control valve adjusts the rate of lowering but not the rate of lift. The oil can the lift cylinder through the check valve. However, when lowering, the oil must pass through the flow control valve in route to the poppet valve and back to the sump. With the flow control closed, a 3ph can raise but not lower. In addition, a properly adjusted 3ph goes out of lift mode before the lift arms reach their physical maximum lift. If the relief valve opens, the condition can be remedied by a position control rod adjustment. Another possibility is that the mower simply exceeded the 3ph capacity. If the 3ph couldn't lift the mower, the relief valve would open and the oil would over-heat if the 3ph remained in lift mode. I wonder if the 750 continued to the same mower after the pump repair? Anyway, it's a story that lends itself to speculation. Since I’m given to speculation, I wonder what type of pump is on a 750 and which types are more prone to seizing. I would speculate that piston pumps might be more apt to seize.
....
Reply to |
Quote Reply |
Add PhotoHydraulic Stop Valve
| Randy
Join Date: Feb 2002 Posts: 76 myLocation
|
2001-09-26 32026
The hydraulic pump was a gear type pump. I suspect that failure was caused by a combination of things, overheated oil and a dead end for the pump oil flow. I have rebuilt a couple of gear pumps before this one that were worn out, but this one looked like something internal made it come to a hault.
The same mower has been used since then with no problems. The one thing different about that day was the operator was a young man who had never operated a tractor before.
Randy ....
Reply to |
Quote Reply |
Add Photo
Go Top
Share This