Ford Tractor Hydraulic System

As with other things, I like to tackle any sort of lift problem by first checking the possible causes that are No-Cost or Low-Cost items. So, how's the weather? That is a good conversation starter, and there is a good reason to talk about the weather, It affects everything.

Has it rained or been humid recently?

Did it freeze last night?

Is it below freezing now?

Do you leave your tractor parked outside?

Is you rubber boot in the shifter in good shape?

How long has it been since you changed the hydraulic fluid?

PHYSICAL DAMAGE

Almost left this one out. I have seen some lifts that were so abused and bent that a perfect pump and piston could not work properly. Straightening and repairing the lift arms and other hardware is mostly just time and energy. If someone has substituted bolts where there should be pins, replace them with the correct hardware. If you don't have tools to straighten what is bent, new parts are available. A shop press is ideal, but creative use of a floor jack or bottle jack and heavy chain can straighten lots of parts. Any improvement will help. BE CAREFUL! Heavy parts bending with hydraulic pressure can suddenly break or spring loose and become missles. Don't put your body under or in line with any force you are employing. I got in the habit of wearing safety glasses 100% of the time in my shop. Wear them enough and you forget you have them on.

MOISTURE

Water in the hydraulic fluid can be very bad. First, it causes rust and corrosion. Even small amounts of water in the pump can cause valves to stick, springs to break, or linkage to bend. Water is heavier than oil, so it collects at the bottom of your sump (where the pump is located).

Water is bad, ice can be worse. Large amounts of water in the sump can freeze and crack the cast iron housings!

Warm things up by bringing the tractor into a garage and/or with a portable heater. Once or if things are already warm enough not to be frozen, get a pan or pail and crack open the three drains at the bottom of the hydraulic sump.

Daily use of your tractor will constantly evaporate any moisture from condensation. But if your tractor has been sitting for a while, or you generally leave it outside in the weather, it is a good idea to drain off any water that may have accumulated in the sump (not a bad idea to also do this to the engine oil sump while you are under there). In humid months, you can collect quite a bit of water in the sump just from condensation.

Carefully loosten a drain plug on the hydraulic pump housing. Get it just loose enough to drain off any water and screw it back tight as soon as you start getting oil. Oil floats on water, so that should get rid of most of the water in the sump. If you get a lot of water (more than a point or so), check your boot on the shifter for cracks. A $5 shifter boot is much cheaper than five gallons of hydraulic oil or a frozen and broken hydraulic pump!

Simply draining off any wateer can fix some problems. If that didn't do it, read on.

CORRECT FLUID

The N tractors have a common sump for the rear end, hydraulic pump and transmission. Therefore, the fluid used is a combination gear lubricant/hydraulic fluid. You cannot use straight hydraulic fluid or straight gear lube in this sump. Gear oil is not a good hydraulic fluid and hydraulic fluid is not gear oil.

The original Ford recommended fluid for the 8N hydraulic sump was "mild EP Gear Oil conforming to Ford specification M-4864-A and B, SAE 80 below +32 degrees F, and SAE 90 above +32 degrees F". The current dealer-recommended fluid is Ambra Multi-G 134 (NH-410B) synthetic fluid meeting Ford M2C134D specifications. The current brand name being sold at the New Holland dealer is Ambra. Some people stick with the original 9N spec. and use a straight 80 or 90-W mineral oil. The modern equivalent of 90w mineral oil is TSC Traveller brand GL-1 or NAPA part number 65-205. The mineral oils are also less expensive than teh synthetic, but the Multi-G 134 synthetic is good from -5 to 120 degrees F, and I believe it is a MUCH better all-season combination hydraulic/gear lubricant for the 9N-2N-8N-NAA tractors.

CHANGING THE HYDRAULIC FLUID

To completely drain the hydraulic system, there are three drain plugs. Two large plugs under the transmission and pump and one smaller pipe plug under the differential housing. There is only one filler cap located on top near the gear shift lever.

When you are ready to drain the sump, you will need a container that holds about 5-gallons.

When changing the fluid, try to flush as much of the sludge as possible out with the old fluid. Just like changing the oil in the crankcase, it is better if you drain it when the fluid is at least warm. It runs out quicker and more stuff is suspended in it. You can use one drain pan to catch the fluid by starting with the pipe plug under the rear end and moving forward to the large plug at the hydraulic pump and then the last one at the transmission. Some people recommend flushing the system with kerosene. They drain the sump, pour in a couple of gallons of kerosene, start the engine, engage the PTO and run the lift up and down a couple of times. Then they remove all three plugs and let it drain overnight. This procedure of-course requires three drain pans.

CORRECT LEVEL

Once the sump has been completly drained, replace the three drain plugs and then remove the bottom bolt from the inspection plate that has the hydraulic dip-stick. Start filling the sump and stop when the fluid begins to leak out of the bolt hole. That is all you need, any more will just leak past the axle seals and get on your brakes. It usually takes 4-1/2 to 4-3/4 gallons not 5 as stated in the owners manual. Pull the dipstick and, if necessary, make a new mark that corresponds to the correct level.

LEAKS

Attach a heavy implement (anything weighing at least 150 pounds should be enough). Remove the right inspection plate that has the hydraulic dip-stick. Start the tractor, press the clutch, make sure the PTO is engaged. The PTO shaft should spin when you release the clutch. Raise the implement while watching the fluid through the inspection hole. Look for leaks coming from above. Small leaks have a tendency to get bigger, but you should be able to judge if your leaks are bad enough to have to remove the top cover and fix them. Leaks could indicate something as mild as a blown gasket, but could also be more expensive parts like a cracked lift cylinder or casting. A mirror can be used to try and pinpoint where the leak is. A new top cover gasket set is pretty cheap.

Removing and replacing the top cover is a relatively simple proceedure that is covered pretty well in the I&T FO-4 manual. The only thing I can add is that it helps to have two people. The lift linkage needs to be guided into place as the cover is lowered. That is hard to do both with only one pair of hands. DO NOT bolt the top cover down until you have made sure the linkage is correct.

if you do need to remove the top cover, that is a good time to check, repair, and readjust the linkage. I can add very little to that proceedure. Check my LINKS page for a link to Zane Sherman's website. He sells a jig and booklet of instructions for adjusting the lift. It is worth every nickle of the asking price. It is possible to repair and adjust your lift using just the instructions in the I&T FO-4 manual.

PUMP PROBLEMS

While you are looking for leaks, you should see some indication that fluid is being sucked into the pump from the sump. no leaks, and no indication of suction, could be stuck valves or something major broken in the pump. Drain off some fluid to expose the top of the pump. This should allow you to see if the excentric cams and pistons are moving properly. There are two piston assemblies that both should move at the same time, and in opposite directions. A "chuckling" sound under load usually means the excentric cams are worn but the pump can make a lot of noise and still work ok. Shuddering on the upswing usually indicates one or more valves in the pump are sticking or not sealing. Rebuild kits can be purchased in various stages depending on what needs to be rebuilt. Once again, I have little to add to the diagnostic and repair proceedures in the I&T FO-4 manual.