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Discussion Starter #1
My owner's manual talks about warming up hydraulic fluid by turning the steering wheel until the wheels stop turning and holding it there. It cautions not to do this for more than two minutes or damage could result. Does anyone know what is actually going on that is warming the fluid? And also, would actuating a lever and holding it down (or up) on something like a rear SCV to which nothing is connected achieve the same thing?
 

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It is sending the hydraulic system into relief, making it heat up quickly. I don't think this is a good idea (or needed) unless its really cold, like sub-zero cold. The fluid will heat up without that since it is being pumped through the system all the time, so running for a few minutes will get it warm enough in most climates, as will the engine oil be warming at the same time.
 

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Discussion Starter #4
So does using an SCV lever to which nothing is attached accomplish the same thing?
 

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So does using an SCV lever to which nothing is attached accomplish the same thing?
Anything that causes the hydraulic pump to go into relief should have the same effect. So dead-headed couplers on the SCV should bog down the pump the same as turning the steering to the stops.

Here is what my 2720 Technical Manual says:

Hydraulic Warm Up ProcedureReason:For accurate hydraulic tests, the oil must be heated tonormal operating temperature of 43°C (110°F).

Procedure:

1. Install JDG temperature gauge on supply line to oilpump.
2. Apply park brake.IMPORTANT: Avoid Damage! DO NOT overheat oil.
3. Start engine and run at fast idle.
4. Operate hydraulic system to create back pressure insystem:
---a. On units without SCV—Use a 13mm open*endwrench to partially close isolation valve, located onside of rockshaft, until system pressure relief valveopens.
---b. On unit with SCV—Operate SCV lever to causesystem to go over relief.
5. Operate until oil reaches normal operating temperatureis within specification.
 

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So does using an SCV lever to which nothing is attached accomplish the same thing?
Yeah, but a better option would be to get a short hose with 2 male ends on it, then the fluid can flow. We did this on the loader tractors at the farm to keep the fluid warm on cold days.
It's amazing when it's -20* even with the equipment working how quick the fluid cools off. Quickly remember to cycle any cylinder on the loader before doing actual work with it (lift, dump, or grapple).
 

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Yeah, but a better option would be to get a short hose with 2 male ends on it, then the fluid can flow. We did this on the loader tractors at the farm to keep the fluid warm on cold days.
It's amazing when it's -20* even with the equipment working how quick the fluid cools off. Quickly remember to cycle any cylinder on the loader before doing actual work with it (lift, dump, or grapple).
Any open center hydraulic system does this normally anyway. The fluid is pumped non-stop and it usually comes through the rockshaft valve and dumps over the rear end gears. Adding a hose would do nothing in this scenario.

On a closed center system, this would cause the pump to work at 100% flow capacity as it tried to maintain pressure in the system. This doesn’t build up the heat like a relief valve would.

Just food for thought.
 

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Any open center hydraulic system does this normally anyway. The fluid is pumped non-stop and it usually comes through the rockshaft valve and dumps over the rear end gears. Adding a hose would do nothing in this scenario.

On a closed center system, this would cause the pump to work at 100% flow capacity as it tried to maintain pressure in the system. This doesn’t build up the heat like a relief valve would.

Just food for thought.
IDK, but it made/makes a heck of a difference on our 4240 and now on the 7700. :dunno:
Never claimed to be an expert, I just know it works. :laugh:
 

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IDK, but it made/makes a heck of a difference on our 4240 and now on the 7700. :dunno:
Never claimed to be an expert, I just know it works. :laugh:
Yeah, I imagine both of those machines are closed center. You are causing the machine to work harder for sure. More work = more heat. But it’s not going to generate the same amount of heat as a relief valve lifting does. Lifting a relief is the quickest way to heat up oil, that’s why it can be dangerous. It’s simply dumping all that power being generated and converting it straight to heat.
 

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Yeah, I imagine both of those machines are closed center. You are causing the machine to work harder for sure. More work = more heat. But it’s not going to generate the same amount of heat as a relief valve lifting does. Lifting a relief is the quickest way to heat up oil, that’s why it can be dangerous. It’s simply dumping all that power being generated and converting it straight to heat.
I think it's more just keeping it flowing, so the pump is warming the fluid somewhat, and warm fluid is constantly being returned to the tank, so it stays warm(er) overall, vs the oil in the hoses and cylinders that are cooling rapidly at -20* :laugh: and thus slow moving for the first cycle.
 

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I think it's more just keeping it flowing, so the pump is warming the fluid somewhat, and warm fluid is constantly being returned to the tank, so it stays warm(er) overall, vs the oil in the hoses and cylinders that are cooling rapidly at -20* :laugh: and thus slow moving for the first cycle.
That’s correct. In a closed center system, the pump will definitely work more as you are dumping all that flow straight back to the tank. The downside is, depending on the hose size and flow characteristics of your pump and hose setup, you could be “handicapping” your tractors hydraulic system. If you couldn’t reach full pressure due to the “leak”, you may not have the full capacity of your system.

As long as everything is working as you need it to on those tractors, I’d say you have a good plan.

This just wouldn’t work all that well on open center systems.

Like I said, just food for thought.
 

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That’s correct. In a closed center system, the pump will definitely work more as you are dumping all that flow straight back to the tank. The downside is, depending on the hose size and flow characteristics of your pump and hose setup, you could be “handicapping” your tractors hydraulic system. If you couldn’t reach full pressure due to the “leak”, you may not have the full capacity of your system.

As long as everything is working as you need it to on those tractors, I’d say you have a good plan.

This just wouldn’t work all that well on open center systems.

Like I said, just food for thought.
Just gotta feed the cows! :bigthumb:
 

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Just gotta feed the cows! :bigthumb:
Honestly, I think your solution is quite clever. :drinks: As long as the hose is sized right, you could “have your cake and eat it too.”
 

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Discussion Starter #14
Yeah, but a better option would be to get a short hose with 2 male ends on it, then the fluid can flow. We did this on the loader tractors at the farm to keep the fluid warm on cold days.
It's amazing when it's -20* even with the equipment working how quick the fluid cools off. Quickly remember to cycle any cylinder on the loader before doing actual work with it (lift, dump, or grapple).
Isn't the fluid flowing all the time anyway? What does adding another short loop to the flow do?
 

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Isn't the fluid flowing all the time anyway? What does adding another short loop to the flow do?
As Jason wrote a few times above, yes. And yes holding the SCV will do the same, but as I wrote unless we are talking about sub-zero temps it's just not needed.
 

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Isn't the fluid flowing all the time anyway? What does adding another short loop to the flow do?
On open-center systems, full flow happens all the time regardless of any hydraulic SCV position or any other uses. So this trick would do absolutely nothing different than normal operation.

Closed-center systems don’t flow fluid unless they are being used, as in steering is turned, loader is lifted, etc. The pump pumps fluid until it reaches pressure then essentially freewheels and does nothing. Once a hydraulic demand happens or a “leak” is introduced, the pressure drops and the pump starts pumping again.

All Cutty is doing is introducing a “leak” in his system. As long as the pump can maintain the flow of his “leak” and not exceed the flow capacity of the pump, he can maintain full pressure or close to it on his system. If the hose/fittings used are too big in diameter, more flow would occur, pressure will drop. The lower the pressure available, the less work the hydraulics can do.

Make sense?
 

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Discussion Starter #17
So which kind is found in tractors? Closed?

I always thought the fluid was continuously flowing/being pumped, with excess pressure being purged through the relief valve, and that only the individual cylinders didn't have flow until used.
 

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Your machine has an Open Center hydraulic system.
That's true for most SCUT/CUT. I believe bigger AG tractors have closed center systems.
 

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That's true for most SCUT/CUT. I believe bigger AG tractors have closed center systems.
And some models could be found with either! :laugh:
 
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