Hydraulics question

Will changing the hydraulic fluid in my Farmall 400 help with a weak pump? It should be able to lift a round bale of hay (1200 lbs +/-) more than a few inches but can't. Either the pump is weak or the bale fork is too far back which is moving the center of effort past the tractors load limits. I am tying get a pressure guage.

I would check the hydraulic pressure to what it is. Hal
PS: Your manual should have what the pressure
should be. Northern Hydraulics has pressure gauges. 1-800-823-4937

Changing oil will only help only if system is dirty,milky (water in oil) metal shavings,etc. Pump may be worn (clearance between pump wall & vanes/gear) also check pressure relief valve, you might be able to adjust the pressure somewhat. But use caution not to overadjust you could trash the pump.

A 400 will lift the front of the tractor into the air like pronto if the hydraulic system is up to par, no matter what excess weight is on the back. Even if the fluid was new, it would probably not help a worn pump. (5-600$) JimN

Like says Seph says, only change the fluid if its milky. By all means check fluid level but you are likely losing pressure in the system.
Remember that Pressure does the work and flow rate determines the speed.

I worked the system and bled air as the manual says. The fluid level is right there at full on the dipstick. It is clean and looks like new.
Guess it's the pump...

I am new to tractors but do my own maintenance and repairs on my other vehicles so is a pump swap relatively straightforward? I have the shop manual.

Have you followed the steps, as outlined in the manual, for troubleshooting a faulty pump??

I know absolutely nothing about your tractor but confirming that there isn't a malfunctioning relief valve, control valve, or pump stroke controller would be at the top of my list to check before simply replacing the pump..................

I will as soon as I can find a pressure tester I will. I have the procedures, just not the equipment. I suspect the pump over the controls because the system WILL lift small loads. Faster with higher engine speeds.

Try a lighter load to see if it will lift it.
You may have a pressure control valve that is hanging up on you and not leting the pressure reach the correct level.

It will lift a round bale an inch or two, I can lift wood/metal fenceposts out of the ground... Seems it will do 500 lbs or so but just can't lift over a few inches after that.

Not being able to lift heavy loads, or as heavy as the tractor use to be able to lift, definitely points towards a loss of available pressure but still does not rule out other potential malfuctioning components.........short of flow testing the hyd. pump there is no way to confirm its efficiency and replacing it will be "on a hunch"............

According to the book what type of hyd. pump does your tractor have?? gear, vane, piston??

If it's equipped with a gear pump the hyd. system will also be equipped with one or more relief valves that may be opening prematurely causing a loss of available pressure......Note: the tractor may be equipped with relief valves regardless of what type of pump it uses, especially if auxillary control valves have been installed......

If it's equipped with with a piston or vane type pump, there may be a malfunctioning stroke control valve that is "shutting the pump off" prematurely or the stroke control may simply need to be re-adjusted due to a weakened spring...........

Also you mentioned you'd be changing the oil.......change the hyd. filters while you're at it(inspecting the old ones for filings- iron, brass, aluminum, etc.) Determine their placement in the hyd. system, if you're lucky and they are "downstream" from the pump you'll be able to tell immediately if the pump is failing by the amount of contamination found in the filter.........

Not to say that the pump couldn't be the problem but there are many other components in a hyd. system that can cause the symptoms you speak of, components that should be far cheaper than the pump too.............

In the shop manual it shows how to remove the drive gear and woodruff key so I will go with geared.
I agree I have to get a guage/tester before arbitrarily swapping parts. The pump goes for $600. The manual says it is unrebuildable except for a seal. Without the tester/guage there isn't a way to narrow the problem.

With the load on the back will it raise the front wheels? a 1200 pound bale is a BIG one. Many farmers have never weighed a big bale.

Yep, getting a gauge would be the safest route............a 0 - 5000/6000 psi. gauge, some fittings for adapting, and a properly built hyd. hose to use as an extension to read the gauge in a remote location should work........