Losing prime on hydraulic pump

I have a 1972 Ford 4000, tractor number C344551, with the 3 cyl gas engine, the select-o-speed transmission, and an independent PTO 540/1000 rpm. It has the gear driven external piston pump on the left side.

For many years, we have suffered with poor hydraulic operation, and I have come to know its symptoms quite well, but to date haven't been able to figure out a solution.

The symptom is that the 3 point hitch is slow to pick up after the tractor has not operated for a few days. The severity of the problem seems to be related to temperature. On cold mornings it takes FAR longer for the 3 point system to lift. I have had some success blowing compressed air into the rear axle housing through the fill plug at the top, under the seat. I believe that the oil is thicker on cold mornings, and it is harder for the oil to move (takes more suction). The compressed air "assists" the oil in moving toward the pump and generating a prime.

I do not think that priming the pump is the solution, as when the oil finally makes it to the hydraulic pump, the action is positive and without delay, and the hydraulic system works consistently until the work is done. Rather, the problem seems to be that the pump is losing its prime after the work is done.

I suspect a leak on the suction side of the hydraulic pump. But, I'm not sure how to find it. Any tips would be most appreciated. Is there a reasonable inexpensive way to do a vacuum test on the suction side?

I suspect that there may be a leak somewhere along, or at the end(s) of, the large diameter suction tube which runs from the bottom right side of the rear axle housing to the hydraulic pump. The parts diagram referenced below shows part number D0NNB835B for "TUBE, Inlet, L/10 Speed Transmission, 3550,4000" and part D0NNB835C for "TUBE, Inlet, W/10 Speed Transmission, 4000". I'm not exactly sure whether I have the "10 speed transmission" or not. I have the Select-o-speed transmission which has 10 forward speeds and 2 reverse speeds. I'm guessing this is NOT the 10 speed transmission referred to in the diagram, and that the correct tube for my tractor would be the D0NNB835B. Do any of you know whether that is right?

As I'm sure many of you know, New Holland has a great parts lookup system that allows for researching detailed part diagrams and part descriptions for even very old tractors like this. Related to the hydraulic symptom I've described above, the closest related assembly diagram I could find is titled:

(10A01) - HYDRAULIC PUMP ASSEMBLY, 2000, 3000, W/INDEPENDENT PTO, 4000 EXCEPT W/INDEPENDENT PTO

A link to this page on New Holland's website is provided.

The title of this assembly is puzzling to me, as it doesn't seem to apply to the 4000 model with the independent PTO. I have a model D1026E tractor, and I believe this means that I have the independent PTO. Yet, I can find no similar diagram for the hydraulic pump assembly which applies specifically to the 4000 model with the independent PTO. I would be most appreciative to any of you that might straighten me out on this point as well.

Thanks for any help and suggestions.

Al
Untitled URL Link

Some random thoughts.
First, welcome to the board.
Ford only built one 10 speed and that was the SOS.
The oil tubes from a 2/3000 will Not fit a 4000 because the 4000 transmission is longer. A 72 should have the seperate tubes for suction and pressure. Older ones had the tubes joined together to a 3 bolt manifold on each end.
It would not be difficult to pull the suction tube off - drain the oil in the rear end first. The tube just slip fits into each end. There is an Oring inside where the tube slips in. I would purchase new Orings from CNH (not the hardware store) and replace them.
I would inspect the tube visually first for possible rust spots, tiny punctures or wear through. Tube would not be hard to test with air pressure. Fashion a wooden plug for one end and apply pressure with a blow gun to the other. Use dish soap to look for possible leaks - bubbles - along the whole tube.
There are a couple of clamps that hold the lines to the body of the tractor. They should have a rubber inside to prevent wear through from vibration. Make sure the clamps and rubbers are in place and no wear through has occured. Suction line can easily be brazed by someone who is adept at brazing.
What oil are you using in the rear end?
You should use UTF or HyTrans that meets Ford 134D specs. Sometimes people put 80W90 in the rear end and that is much thicker than UTF - harder to pull.
When slipping the tube back into the new orings I always wash both mating parts with lacquer thinner then apply a TINY amount of silicone on the tube. Like about 1/2 the amount of a dime or just enough to "wet" the tube. You don't want to gob a bunch on there and get it into the hyd controls or pump.
After inserting the tube wipe the excess off all around the tube with your finger.
Lastly - and least likely - your pump might be getting old and needs rebuilt. Not hard to do and parts are sold here at this site. The pump on your tractor is the same as a 23000 pump of that year. Less confusing to order parts for a 3000 pump.
Probably others here have more thoughts and will reply.
Give us an update on this. Your findings will be read by many and add to the knowledge base here.
PS, if you have to remove the pump or pressure line for any reason or need to replace the rubber compression nut that holds the pressure tube in DO NOT just wiggle the metal retainer off the end of the tube.
That will scar up/gouge/eat away the outside of the tube and a new nut will Never hold again. Carefully grind most of the way through the metal retainer on two sides then break it off. A good used tube for a 4000/3550/4400 or 4500 will be hard to find used and a new tube from CNH will likely require a second mortgage on your farm.
Sorry this got so long...

The title of this assembly is puzzling to me, as it doesn't seem to apply to the 4000 model with the independent PTO.

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I agree that the description of what models that pump is used on is confusing.

The S-O-S independent PTO was different than on the other 3 cylinder 4000 tractors that had manual transmissions, which also had independent PTO, but the PTO on the manual trans models had their clutch pack inside the rear axle and the hydraulic pump was inside the rear axle as well, and that pump had two separate pumping sections, one for the 3 point lift and the other for the PTO clutch. So the description for that pump really should be "2000,3000, 4000 w/10 speed, 4000 l/10 speed & l/Ind. PTO"

Ultradog has steered you right on your questions on the part numbers for the tube and o-rings.

Thanks UltraDog. I really appreciate the detailed and thoughtful reply. I will post my findings on this thread in hopes that my experiences may help others.

"Ford only built one 10 speed and that was the SOS." That's what I was thinking originally too, but then saw that Ford made a manual transmission with 8 forward speeds and 2 reverse speeds, totaling 10 speeds, and got confused. Assuming you are correct that I have the 10 speed transmission, the D0NNB835C tube would appear to be the correct one. Messick's can not supply this part.

Yes, I have separate tubes for suction (large diameter) and pressure (small diameter).

I just received the o-rings for the suction tube from Messick's. I will give the suction tube a good visual inspection, and I like your idea of pressure testing the tube. I also like the idea of cleaning with lacquer thinner and using a small amount of silicone to seal.

Not sure what oil is in the rear end at this point, it's been a while. I do not think I used 80W90 oil, but may have used a generic hydraulic/transmission oil.

The hydraulic pump has been rebuilt twice. Once by a tractor repair shop, and a second time by a friend of mine who is an excellent mechanic. Neither effort produced any improvement in the symptom we are experiencing, so I am in agreement that this is an unlikely solution.

Thanks again for your post.

Al

Sean,

Thank you. As I read your post, I think you're saying that the 10A01 assembly diagram applies to my tractor. Right?

Al

Would a silicone based lubricating compound such as Sil-Glyde be better than 100 percent silicone for this application?

I don't know what sil glide is so can't say.
The name sounds like that K-Y stuff. wink
I do know regular silicone works.

(quoted from post at 10:36:35 07/08/18) Sean,

Thank you. As I read your post, I think you're saying that the 10A01 assembly diagram applies to my tractor. Right?

Al

Click to expand...

Yes, I have a 1973 gas engine 4000 with S-O-S transmission which should be the same as your tractor according to your description, except that mine has the single speed 540 rpm independent PTO, so my model number is D1024E instead of D1026E, and that drawing applies to my pump.