The cam follower pin/dowel may be cut into or missing from the linkage.
The gasket between the top of the ram cylinder and the bottom of the lift housing may be blown.
If there is a large volume of oil spraying down from above after the inspection plate has been taken off and observed you can bet it is the ram cylinder gasket. A blown or worn out ram cylinder Oring and back up ring may be a cause too.
The pressure relief valve could be leaking or stuck open with some sort of foreign material between the ball and the seat. The pressure relief valve on the NAA must be accessed by removing the top lift cover because it is on the back side of the ram cylinder. The later model tractors have it under the remote control valve adapter cover on the top of the lift housing.
First thing you need to do is before starting the engine take out the bleeder plug at front top of the piston pump. If their are a lot of bubbles comes out first before the oil becomes free of bubbles you may be loosing prime. If not then you have a sticking or immovable unloading valve in the lift. Or some other part has come loose or the cam follower pin has worn to a critical point
Remove the right hand inspection plate and with an implement in the lift arms try to lift and observe inside for any flow of oil caused by an internal leak around the ram cylinder. There should be no oil coming from above except for a small drip from the control valve section and this is from wear in the spool and bushing and if small is acceptable.
You need to be sure that the big flat O ring that goes between the backpressure valve and the right side of the lift is good and not leaking when you take the lift off. Do you know the procedure for removing and replacing the lift in relation to the backpressure valve@ the acorn nut etc.? It is under the big acorn nut that is located on the right side of the lift housing . The nut must me removed and the large hollow stud must be turned at least two complete turn to the left counter clock wise so the back pressure valve will be clear of the internal lift components when the lift cover is removed. Do not turn the hollow stud too much or you will damage the back pressure valve and the unloading valve will not work if the backpressure valve is inoperative.
Remove all the linkage to the 3 point hitch so that the lift assembly is free of all attachments. Remove all the bolts from around the outside edge of the lift housing assembly. Do not remove any bolts that are not along the outside edge. If you encounter a bolt with fine threads it should be reinstalled.
Remove the 3 bolts that hold the triangular plate toward the front of the lift assembly that is a part of the ram cylinder assembly. Pull the plug that is over the unloading valve by tapping the end of the unloading valve that is accessible through the opening in the rear facing portion of the housing. Use a flat punch and only enough force to cause the plug to be displaced. push the unloading valve out with a punch etc. I have read that the unloading valve can be replaced on the NAA with the later than 100 series unloading valve such as the thousand series three cylinder tractors but have never come across that myself. If it did have the later unloading valve the plug will have a female threaded hole in it to attach a puller to remove it. Replace the O ring attached with the Ford Part #NCA 836 B or the current replacement number O ring and nothing else .Not a parts house O ring. You will be sorry! An aftermarket gasket and O ring kit will have the correct O ring for the unloading valve. This O ring leaking can cause hiccupping and leak down too. Polish up the unloading valve with 300 grit paper and hone out the bore with the same on a pencil or dowel wrapped with sandpaper. Examine everything for missing bolts or pins and linkage hanging loose etc. Closely examine the cam follower pin for excessive wear. The cam follower pin is the main thing that caused the lift to not attain it’s maximum lift height. If it is worn replace it.
Name: ZANE E-Mail: wzsherman@aol.com Subject: Re: Ford 600- Lifting Body of Message: There is a cam cast on to the rocker shaft that is inside the lift housing. This is what the outside lift arms are attached to. The ram rod for the lift cylinder's rear end is attached to the lever cast beside the cam. There is a cam follower that is pressed into the control linkage. It is a pin of approx. 5/16" diameter and one inch long. There is no lubrication at this point in the lift and the pin wears out causing the gradual lose of adjustment travel. The pin must be replaced and the linkage re adjusted as per specifications which I don't know off the top of my head and which usually takes a feeler type gauge to measure between the control valve head and the cylinder housing where the control valve goes into the spool in the housing. Now is definitely the time to replace the cam follower pin. That much wear does make a lot of difference in how the lift works and when it starts to lift according to where the lift control is positioned. I would definitely obtain the correct part to replace it with. Don't go with a cut off bolt etc. as it will wear down too quick. If you are going to consider using a bolt etc you may as well leave the old pin in place because with it worn half way into it out last a bolt etc. . The replacement is a hardened pin and it has to be hard to prevent rapid wear. There is no lubrication to the pin. Be sure and support the linkage as close to the pin hole as possible while driving the pin in or out. You can do this by holding a long heavy flat ended bar by the pin as it is driven out with a punch of correct diameter. Usually takes two people to do it. One to hammer and one to cuss. Added on Date: 05:50:33 2/14/99 Added on Date: 03:53:56 7/10/99
The 20 w oil probably would not have any effect on the operation of the lift unless it could have in some way caused the O ring on the unloading valve to change shape. The 134 oil is what I would use. However you guys who are where it goes down to 0 deg probably could use a lighter oil better. I would first try bleeding the pump by removing the front pipe plug with the Allen head hole in it. Start the tractor and let it idle as slow as possible and when all the bubbles are gone stop the tractor and put the plug back in. You will loose about a half cup usually so put something under the pump to catch the oil. If it won't work then you must go into the lift and take out the unloading valve and clean it up and replace the O ring with the Ford O ring made specifically for the unloading valve. The old part # was NCA 836B. Don't use a substitute or you will be sorry. It is a good idea to replace the back pressure valve or at least see that it is working properly.@ has some resistance to air pressure etc .Also be sure the big O ring that seals the back pressure valve to the side of the lift is in good order. The back pressure valve must be disengaged from the side of the lift housing inside by removing the large acorn nut on the right side of the lift housing and backing the large hollow screw out counter clock wise till a light resistance is felt. Stop unscrewing then as you will damage the valve if force is used past when you feel resistance.
The back pressure function is to allow for the movement of the unloading valve. The unloading valve is what makes the lift begin to move once the control valve is moved. The control valve itself does not move the lift. The unloading valve is covered by a plate at the front of the control valve housing just above the control valve. The unloading valve is covered by a 25cent size plug.. The valve can then be pushed out with a punch of the appropriate size. By slightly tapping the end of it till the small plug pops out The O ring will be on the unloading valve that needs to be replaced. If you will look around on the other reference pages of the N board etc you can probably find some good views of the lift to give you some idea of what you will be looking at. When taking the lift control housing off the tractor remove only the bolts that are around the ;outside edge of the housing and do not remove any of the bolt that are inside this circle of bolts. If you encounter a bolt that has fine threads on it put it back where you took it out. The fine threaded bolts hold the cylinder to the cover housing. Good luck Zane in Al.
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Today's Featured Article - Hydraulic Basics - Part 2 - by Curtis Von Fange. In the last entry to this series we gave a brief overview of hydraulic system theory, its basic components and how it works. Now lets take a look at some general maintenance tips that will keep our system operating to its fullest potential. The two biggest enemies to a hydraulic system are dirt and water. Dirt can score the insides of cylinders, spool valves and pumps. Wate
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