Can someone help me understand the theory of the LA402 hydraulic valve. I see two hoses coming from the tractor hydraulic block, one out and one into the hydraulic block. The other hose to the tractor in the rear to the hydraulic tank. Why do you need 2 hoses from the tractor block? It would seem that you get pump pressure from both holes in the hydraulic block as fluid passes thru the block to the rear area of the tractor at all times. How could one be in, and the other out? The book says one side of the hydraulic block is out and one is in. What does the LA402 valve do with the fluid it receives? Does it send it back to the hydraulic block or back to the rear tank in the tractor? thanks in advance.
understanding B7800 hydraulics
- Thread starter ToddP
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MadReferee
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The loader valve is in series with the hydraulic circuit. The circuit is broken at the hydraulic block.
The pressure side of the hydraulic block goes to the loader valve's inlet port. The power beyond port of the loader valve connects back to the hydraulic block thus continuing the circuit. The third hose is for the neutral pressure exhaust fluid from the cylinders to return to the tank/sump.
This is the typical open center system where fluid is always flowing so the valve must pass fluid thru when all spools are in neutral. That's why you have 3 hoses from the loader valve, a high pressure inlet, a power beyond to continue the high pressure, and a return to tank for the neutral exhaust fluid.
The pressure side of the hydraulic block goes to the loader valve's inlet port. The power beyond port of the loader valve connects back to the hydraulic block thus continuing the circuit. The third hose is for the neutral pressure exhaust fluid from the cylinders to return to the tank/sump.
This is the typical open center system where fluid is always flowing so the valve must pass fluid thru when all spools are in neutral. That's why you have 3 hoses from the loader valve, a high pressure inlet, a power beyond to continue the high pressure, and a return to tank for the neutral exhaust fluid.
OK, so to hook up a Massey 1217 backhoe I should break the line between the LA402 and Hyd. block where fluid returns to the PB and install a valve that will allow flow to continue to the rest of the tractor in position A. Then, hook the hoe to Position B (with quick connects) so that fluid flows out of the tractor to the LA402 then thru a valve, thru the hoe and back to the PB inlet on the Hyd block. Does all this sound OK? I assume from looking at the hoe that I don't need a 3rd hose to return fluids to the tank since there doesn't appear to be a place for a 3rd hose on the hoe? Will this hookup permit full GPM to the hoe or will the LA402 valve impose restriction to the GPM? Would a valve such as this work: http://surpluscenter.com/item.asp?UID=2005062319045240&catname=&qty=1&item=9-6238
Thanks for the lesson....
Thanks for the lesson....
guyrj33
Silver Member
I have a woods BH on my B7800, the dealer hooked it up to the 3 pt hydraulics. I think they broke the supply hose and connected the BH in series. It uses quick connects and dealer said just connect the ends together if I remove BH.
Caveat: I don't like the way the BH works, can't seem to run both backhoe controls at the same time. e.g. raise boom and pull dipper in. One control or the other gets all the fluid, unless you are extremly gentle with the levers.
Caveat: I don't like the way the BH works, can't seem to run both backhoe controls at the same time. e.g. raise boom and pull dipper in. One control or the other gets all the fluid, unless you are extremly gentle with the levers.
MadReferee
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</font><font color="blue" class="small">( think they broke the supply hose and connected the BH in series. It uses quick connects and dealer said just connect the ends together if I remove BH. )</font>
That is the typical way to connect a backhoe that does not have power beyond. This will preclude using the 3pt efficiently but since you can't use it anyway with a 3pt backhoe it makes no difference.
</font><font color="blue" class="small">( Caveat: I don't like the way the BH works, can't seem to run both backhoe controls at the same time. e.g. raise boom and pull dipper in. One control or the other gets all the fluid, unless you are extremly gentle with the levers. )</font>
This is a function of the backhoe valve design and the amount of fluid available (ie. gpm). The open spool closest to the backhoe inlet usually will get priority for fluid flow but alot depends on what it is controlling (size, volume needed, etc.)
That is the typical way to connect a backhoe that does not have power beyond. This will preclude using the 3pt efficiently but since you can't use it anyway with a 3pt backhoe it makes no difference.
</font><font color="blue" class="small">( Caveat: I don't like the way the BH works, can't seem to run both backhoe controls at the same time. e.g. raise boom and pull dipper in. One control or the other gets all the fluid, unless you are extremly gentle with the levers. )</font>
This is a function of the backhoe valve design and the amount of fluid available (ie. gpm). The open spool closest to the backhoe inlet usually will get priority for fluid flow but alot depends on what it is controlling (size, volume needed, etc.)
After looking at the hydraulic block on the tractor, I am wondering what size the connectors are. /forums/images/graemlins/confused.gif It seems to be a JIC fitting, but what size I am not sure. Seems like you can get JIC 4, 5, 6's in 1/4". The hole in the fitting seems to be 1/4", but the loader is connected with 3/8 hoses. Is there a way to measure them to arrive at the correct JIC connector? Do these come in metric? thanks again /forums/images/graemlins/smirk.gif
MadReferee
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The female thread on the JIC connector is 9/16-18, commonly referred to with a suffix of -06 or sometimes just as 3/8 JIC.
It is also a 37 degree flare.
It is also a 37 degree flare.
I have hooked up the hydraulics on the hoe as prescribed here in this forum by opening the return line back to the Hyd. block from the loader. The loader still works fine, but the hoe doesn't. Let me add that the hoe was empty of all fluid prior to me owning. I have topped off the fluid several times as it fills the hoe. The hoe will not operate. The only thing I got it to do is drop the arms and jack up the tractor and moved the bucket a bit in one direction and the one cylinder just before the bucket in one direction. Now, nothing moves except for minor jerky attempts at cylinder movement. It sort of appears that the cylinders are slightly moving in a direction opposite of the pictures by the sticks. I am wondering if the supply and return lines are reversed? Is this possible? Any thoughts? /forums/images/graemlins/confused.gif
Picture of valve attached.
Picture of valve attached.
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MadReferee
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Your picture does not tell us much. Where is the inlet hose and where is the outlet hose? If there is a relief on the valve it will be on the inlet side.
The lower 2 hoses(Most left/most right) are the in/out. In a previous post, somone told me in is on the left and out on the right. I assumed this correct and hooked up this way. Since you say if it has a relief, that would be fluid into the hoe, that is backward to how I have done it if I am to assume the silver thing on the right top valve is a relief shown in the picture. I will try reversing the in/out hoses and give it a try.