# 72 Deere 4320 hydraulics



## treyrooster (Mar 22, 2021)

I’m loosing all hydraulics when pressing the clutch in within a few seconds. I know the rear pump is driven by the engine and the clutch has to be engaged for it to pump. I tested the main pump at the rear remotes and had a little over 2200psi. I also pulled the plug from the trans oil filter housing and ran it at idle for 12 seconds it pumped out around 1 gallon somewhere around 5gal/min. Both of my tests now have me puzzled from what I’ve read both seem ok. Anyone have any thing else or any ideas?


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## Tx Jim (Jun 30, 2014)

My guess is high pressure internal leak at pto control valve, scv or rockshaft control valve


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## treyrooster (Mar 22, 2021)

Tx Jim said:


> My guess is high pressure internal leak at pto control valve, scv or rockshaft control valve


What is the best way to find these possible leaks, feel for heat at each of those valves?


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## Tx Jim (Jun 30, 2014)

I suggest utilizing a laser thermometer to detect variation in temperature. PTO control valves of this type have a long history of failure. Remove plug located to the right & above rear pto shaft & with hyd oil at operating temp look in hole for moving oil which would indicate a hyd leak.


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## Wethay (Jul 17, 2015)

Try engaging the pto and see if anything changes. That directs oil to the pto clutch and does not pressurize the pto brake.


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## treyrooster (Mar 22, 2021)

The pto valve is 116 degrees while the other hydraulics are around 75. Is this valve hard to rebuild or is the issue usually the housing?


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## Wethay (Jul 17, 2015)

If there is no fault, the oil going through the pto valve is either going to the pto clutch or brake and dead ending there. That means when oil flows it is a relatively small amount and for a short time. If the valve was leaking oil it would heat up but I would guess if the circuit was leaking oil somewhere after the valve causing the valve to heat up as it was not designed for continuous flow. At least some of the older John Deeres had a problem with the pto brake band wearing through and then the pto brake piston had no travel limit and would pop out of it's bore. This usually was easily diagnosed by engaging the pto. If the tractor had hydraulic problems, usually severe, that went away with the engagement of the pto that indicated a big leak in the brake circuit, most likely a displaced piston. I have also seen a internal hydraulic tube split causing problems with the pto circuit.


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## Tx Jim (Jun 30, 2014)

Wethay
My thought without aid of 4320 tech manual is what route does return oil from pto valve travel to get back to reservoir? I think return oil from pto control valve is routed back to trans case via a galley in clutch housing. Therefore if pto control valve s leaking internally to sump other than heat will be difficult to determine. I suggest to disconnect & cap supply line to PTO control as a hyd test.


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## treyrooster (Mar 22, 2021)

I also tested hydraulics with and without the pto engaged and it makes no difference. I did notice that the first time of using the hydraulics with the clutch pressed everything functions for longer (probably able to raise the loader up and down 3 times) but after that I’ll release the clutch let it set for a few seconds but the loader will only lift half way about 10 seconds of use


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## Tx Jim (Jun 30, 2014)

What type hyd valve(scv or ind) controls the FEL?


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## Wethay (Jul 17, 2015)

Are there any other hydraulic faults with/ without the clutch depressed? I assume that if you pull the tractor out of gear and release the clutch pedal the loader then works as it should? If your FEL operates off its own valve is it plumbed to dump oil into the transmission or into the hydraulic filter? It does point to a internal leak, but that leaves several places to look.


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