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Eastern Ontario | Working on a 40 series JD SCV. I've installed new valves with new O-rings everywhere. Had to take out the cams as the detend cam roller was worn flat. Put in a new one and put everything back together like it was. I have the manual and adjusted the the valve timing as per instructions. Tested the SCV on the tractor. Right outlet gets pressure while the left outlet gets "0". What the heck???? Any ideas on what could have gone wrong. I think that even if the adjustment is a little off, there should be some pressure on the left outlet, but there's none. I'm stumped. Someone point me in the right direction please. |
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West Central Iowa | Are you sure you have the two cams in the correct location and pointed in the correct direction. The float cam is the shorter of the two and goes to the numbered side (RH side when valve is ON the tractor) of the housing. Also the pointed end of both cams need to go towards the detent roller. About the only other thing I can think of would be if you were not in the neutral position when you adjusted the valve clearance. |
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Eastern Ontario | I've gone and redone the procedure another 2 times. I believe the problem is elsewhere. Sometimes I would have pressure on both couplers and sometimes I would have no pressure at all on either side. I have connected a hose to the outlets and no oil is flowing but the tractor makes a distinctly different sound when the lever is being moved. This one has got me puzzled. I will take the SCV from the other side of the tractor and interchange it with this one and see if the problem moves with it. I've never had such a hard time finding a problem before. Is it possible that something with the rockshaft could cause this problem. The problem SCV is on the left hand side of a JD 4440 and from what I can see it is being fed from the rockshaft. I'm not sure but I think that the right hand side SCV gets fed first and then heads towards the rockshaft and then to the left SCV. If something is not right on the rockshaft then maybe the SCV doesn't get fed, but it doesn't explain the change of sound coming from the tractor. Strange. |
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Mid-East Nebraska | Can it be that you have the lever adjusted wrong that it is in half float and also on, so that the oil is going from the pressure to float and not to the coupler, have seen this before. |
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Princeton, MN | Did you put o-rings on the stem of the return valves? Because there is not supposed to be. Do you have an IT manual or the actual deere one?
Are you using the JD tool to adjust or doing it by sight? I have not used the tool to adjust one in a long time, I just make sure it is in neutral and adjust it so the return valve opens a little bit before the pressure on each side. Before you put the valve on the tractor air test it to see if it leaks in neutral and then move the valve both ways and see if air comes out the coupler when it is open. |
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West Central Iowa | The change in sound you are hearing is the load on the engine increasing when the pump goes into stroke to pump oil and trying to maintain standby pressure. I am pretty sure the problem is in this SCV. The change in sound is from the pressure and return valves from the same side being open at the same time, creating a large hi pressure leak to return. Are you sure you have all of the parts installed correctly. When you say you redone the procedure two times are you just talking about just the adjustment or did you verify that you have all the cams installed correctly? Are you sure you have all the other parts installed correctly? |
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Lapel, In | Did you leave the cam screws slightly loose until you completed the valve adjustment? Are you sure the detent roller was fully engaging the center cam in the neutral position ? You are using an adjusting fixture aren't you? Are you using a dial indicator or the old fashioned , but good 1/8 & 1/4 turn settings ? Upper left hand and lower right hand set at 1/4 turn looking at the adjustment screws Upper right hand and lower left hand set at 1/8 turn. |
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Eastern Ontario | I have taken the whole thing apart at least 2 times. I have the JD tech manual and I am using a homemade tool. Flat plate with 4 screws holding the valves on their seat, just like in the book. I'm also using a dial indicator to measure the play. In my opinion, I don't think I did anything wrong. The cams are right side up,pointing in the right direction and on the right side. I compared two shop manuals to make sure. Even if the valves would be a little off,(which I don't think they are), shouldn't there be even a little oil coming out of the coupler? I didn't do an air leak test. I should probably try that tomorrow. If I can't find the problem tomorrow, it's going to get the sledge hammer fix. I looked for cracks in the housing, but I can't find any. Why is it that sometimes it works and other times it doesn't??????? Wife says I look a little balder tonight.LOL |
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Eastern Ontario | Yes Bob, I've almost got it memorized. The odd thing was that the detent roller was worn flat. I replaced it with one I had on hand. It was identical ( not flat of course ). If these SCV's weren't so darn expensive, I would have put a new one on. Seem to be a hot item for salvage yards as well. |
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Eastern Ontario | I adjusted it where I thought was the center neutral position. The rocker is parallel with the housing.
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Lapel, In | Can you still buy a new one ?I have also seen the detent roller worn flat and on occasion found the roll pin broken.. Got one in the shop today.Detent not holding Found the shut off stop was missing its o ring. Had a feeling something didn't go together right. Finally figured out the chamfer on three valve bores are rough and grabbed the back up washers and wedged the valve guide so tight I had to dismantle the thing and drive the valves back out. Rebuilt a lot of them , but never had anything like this happen before. I usually force them in over the valve stems with a hammer handle , but, in a hurry, just tried to force them by tightening the cover bolts today .I'll never try that again. I should have investigated a little bit before forcing them. Now that I think about that missing o ring, makes me think someone might also have messed up those chamfers? How I don't know?
Everyone around here has quit using the dial indicator to adjust them and gone back to the old 4010-4020 method. Its a lot easier and quicker with fewer problems. Maybe you already do this: Bench test them by using a break away ISO coupler charged with air. You can fine tune adjust them that way.
Edited by msb 4/11/2008 22:33
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Ayr Queensland Australia 4807 | Did you have lever 31 off valve 25 have seen this before when its on full flow their is no flow.
You have covered most other items cam position and direction , how about the valve roller sitting on the cams ,are the cams sitting up straight and against the adjusting screws ensure the cam retaining screws are finger tight and witha smal screw driver lever the lighly up against the adjust screws then nip the cam retaining scews . Does the tractor hitch work , pat may have said about the orings on the two pressure valves ,the cam carrier should sit level with the housing face when in neutral .
My bet is on the flow control if you had the roll pin out
Edited by KelB 4/12/2008 02:24
Attachments
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 scv.mht (39KB - 280 downloads)
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Eastern Ontario | I switched the the two SCV from one side to the other. It appears that the problem did not migrate which leads me to believe that the left SCV is not being fed by pressure oil. There are no obvious lines since the oil channel seems integratded with the rockshaft housing. Now I need to find the oil flow schematic in orderto get to the root of this thing. I hope I don't need to remove the rockshaft and lift the cab. That wouldn't be funny. |
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Eastern Ontario | Couldn't find the exact passages for the oil supply, so I played around with the 3 pt hitch. Up,down,draft control min,max. Every once in a while it would give pressure to the SCV. After a few cycles, the SCV worked flawlessly. There is no reason for me to remove the rockshaft control housing at this point. The 3 pt. never gets used anyway. So the exact cause is not determined, but I'm betting on a stuck valve which worked it's way free. I knew it wasn't my SCV adjustment. I can sleep better now. ;-) Thanks for the help guys. I love this site. |
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SCV adjustment
