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 | Mike
Join Date: Posts: 1 
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2001-05-09 27994
Whenever I lift my implements, i.e., box blade or finish mower, a relatively loud screach can be heard. This only happens under load and primarily when RPM's are up. At idle the implements are lifted and I hear no screach. Additionally, the problem is made worse if I try to slowly lift the implement as opposed to jerking it up. Just changed the hydraulic fluid. No improvement. Any ideas?
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| Bill Schild
Join Date: Posts: 1
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2001-05-10 27998
Mike:
When I activate the 3ph lift on my B6100(no position control) and it is already in the full up position, I get a loud screech too. I'm pretty sure that's the pressure relief valve activating.
I get a similar screech whenever I operate my FEL (separate hydraulic system) in cold weather. That's the pump cavitating because the oil is too thick to flow fast enough to keep the pump full.
Is your screech coming from the 3ph valve area or the hydraulic pump area?
Bill ....
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| Roger L.
Join Date: Jun 1999 Posts: 0
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2001-05-10 28003
What you say makes sense with it being the pressure relief (bypass) valve. They are a common service point and so are always easy to get to. An easy and inexpensive permanent diagnostic tool is to put a T somewhere in the high pressure line and mount an oil-filled pressure gauge. Then you can see at what pressure the valve is actuating. I suspect that either your 3pt load is too heavy or your valve is opening too soon. The valve itself is usually a spring, a round ball, and a couple of shims.
As Bill says, a pump cavitating with too little fluid or fluid too cold to flow will also make a noise. That is a lower noise more of a rattle than a squeal. Also like he says it comes from the pump itself, not the valve area.
Either way, it sounds like a common enough thing that most of us have seen it before and can figure out a fix. A bigger problem is when the system can't generate enough pressure to make the relief valve squeal! ....
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| Mike
Join Date: Posts: 1
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2001-05-10 28019
Roger and Bill, the sound is definitely coming from the control valve assy as evidenced by the craftsman flat blade stethescope. The manual shows an adjusting screw presumably to increase or decrease pressure on the spring. I will give that a try and see what happens.
Thanks for your help.
Bill, by the way this is a B6100. It has been a workhorse and will continue to be until I can save the pennies for the B7500. It's hard to convince the better half that I NEED it, especially when this one continues to run.
Mike ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley 
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2001-05-11 28029
There is some risk in doing a blind adjustment on a pressure valve. An actual pressure test would be good, so the relief can be set to the proper spec. I don't know how the tractor is set up, but my Ford 1710 has the system pressure relief valve built into a hydraulic manifold/divertor block that is mounted on the engine. There also is a relief valve in the 2ph and probably one on the loader SCV assembly. I believe the latter two valves are intended to protect against load shocks, and they are set considerable higher than the system relief valve. There may well be more than one relief valve on the tractor, and there may well be some reason for the valve to be opening other than low adjustment. The situation seems a good excuse to buy a pressure gauge that should remain useful for decades. I still need an excuse myself. ....
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| Roger L.
Join Date: Jun 1999 Posts: 0
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2001-05-11 28038
Most hydraulic systems have a hex or square-headed plug that can be removed and a pressure gauge inserted for this very purpose. THis is because it is almost impossible to diagnose hydraulic systems without knowing the pressure. If you are shy about taking plugs out of the hydraulics, the shop manual will surely point to the system pressure inspection plug. Better yet is too know the pressure and flow, but that is more elaborate equipment. I use a simple pressure gauge that I got at the surplus shop. It is just like the ones from the welding shop except that mine is liquid filled. The liquid fill is not necessary, just nice to have. One from the welding shop will work fine. Get the range 0-5000 psi and make sure you can read 100 psi increments around 1000 to 2000 psi. You will also need an an adapter to go from the thread on the gauge to the NPT thread where you remove the inspection plug from the hydraulic system. That's all. Less than $20. Now you can check it any time you want. Or, just leave it in the system and by watching the pressure you can back-calculate the weight of the 3pt implement! You can also T into one of the lines to the loader, insert another gauge, and watch what happens to the pressure as you lift and dump..FUN! ....
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