John Deere 401C Accumulator

[JohnDeereFarm]

Hello to everyone out there. I have a 1975 John Deere 401c. It has an accumulator on the right side of the tractor. I'm never going to put a loader or a backhoe again. Just going to use the tractor to bush hog with. My question is, do I need the accumulator for the power steering or can I just bypass it. I know that the 2030, which is the agricultural version of this 401c, it doesn't have the accumulator. So do I need it ?

 

[J_J]

Do you have any idea on how the accumulator is used in the present configuration?

In some situations, it is used to smooth out pulsations.

It is also used to supply more power than the pump can generate in a short time frame.

It is also used in some braking situation when the engine is not running.

 

[JohnDeereFarm]

I knew that it does smooth out the hydraulic fluid that is coming from the pump. I also have a 1971 John Deere 2030 and the power steering line is tee'ed off of the line that run to the rear hydraulics. The 401c by the way has a hydraulic reverser on it and the line pulsates that comes from the front pump. Feels like it is starving for fluid. If I were to just charge the accumulator, would it make a difference? Thanks to all.

 

[JohnDeereFarm]

I bypassed the accumulator and it is still the same. I talked to a JD mechanic and he said that it really doesn't need to be on there.

 

[Wayne County Hose]

I bypassed the accumulator and it is still the same. I talked to a JD mechanic and he said that it really doesn't need to be on there.

If it is tied into the steering they use it for a couple purposes. To eliminate steering kickback and to prevent a lag in pressure when other demands call for additional flow. Ask 3 mechanics you may get 3 different answers. Why did you not want it on the tractor?

 

[JohnDeereFarm]

It cost to much to rebuild it.

 

[J_J]

I noticed you have closed center hyd system, and in that system, an accumulator is used to provide the initial burst of fluid, and as the pressure decreases in the closed center system, an unloader activates the pump to build the pressure back to operating pressure. The unloader then releases the fluid to tank, and the pump does not have to work very hard.

They do smooth out the pressure pulses.

The fluid is trapped in the accumulator by a check valve. You might rebuild the check valve, new gaskets, reseal the unit. Recharge with gas.

You did not say it was leaking, doesn't work, or you just did not want it. Some are gas charged and may need recharging, and some are spring loaded. They are very dangerous, and you should be aware of the potential for injury.

Some of the Power-Tracs have accumulators, that are used in the brake system.

The accumulator is sized such that the system pressure will not fall below a value as to degrade system performance.

So if you are thinking about removing it, it probably serves a good purpose.

 

[J_J]

Just some more data about accumulators.

Excerpts:


Use an accumulator, placed as close to the valves as reasonably possible. It should be
sized at least 10 times larger than the change in the volume of oil.


Pre charge the accumulator to 80% of system pressure. Any oil in the accumulator that is
not being used reduces its effectiveness. The nitrogen bubble should be as large as
possible as long as there is always some oil in the accumulator.

Some of the data suggest that about half of the accumulator volume should be fluid.

 

[JohnDeereFarm]

I'll keep that in mind. Thanks for the help!

 

[IceStationZebra]

"I bypassed the accumulator and it is still the same."
If it is indeed broken why would you expect to see a change?

I couldn't find a hydraulic diagram online, but I did find a spec sheet that lists the accumulator precharge pressure at 475-525 psi.

The clutch and reverser pressure is listed as 155-165 psi. So the accumulator can't be on this circuit.

The loader relief was 2750 psi and the hoe relief was 2375-2500 psi. These are ~5x the precharge pressure. Normally the precharge is 60-90% of the circuit pressure so I seriously doubt it is used on either of these circuits.

That leaves brakes and/or steering. Personally I would be hesitant to remove it for safety reasons. Without it there could be some scenario that you haven't encountered yet that causes a loss of functionality. But if you are optimistic that scenario could require a hoe or bucket, which you say will never be used again, so you might be OK. Who know? :confused3:

If it is a piston style you may just need a recharge, they do slowly leak down over time. You could screw it off and take it to a hydraulic shop to have it refilled, shouldn't cost much. If it still leaks then it probably just needs new seals, much like a hydraulic cylinder.

If it is a bladder style, given the age of the tractor, it is probably shot and needs a new bladder. Some can be repaired while others are throw-away.

ISZ