Ford 641 3 point hitch lift issue

[bobsphotos]

I just purchased a Ford 641 to use as a dedicated chipper tractor and I have an issue that I need to get fixed. The former owner said that if the 3 pt hitch would not lift, partially remove the threaded plug on the Hyd pump to remove the air. Sure enough it is an issue. If I purge the air, it will lift ok for about a day. My first question is, what the issue might be and what the fix might be. Is there an easier way to purge the air? I will not be using the tractor daily, so if there was an easier way or a cleaner way to purge it, I would be fine with that. All fluids have been replaced with UTF fluid. ( except the motor) This will most likely be the first of many questions so I will appreciate any help. One thing I need to add. The hyd level was spot on after I changed it and now it is showing very high on the dipstick. How much of an issue is the high level and what is the chance it came from the transmission or rear end? I have attached several photos.

Bob W

 

[downslope]

I've got basically the same tractor (2000 4-cyl) and also experience the same "problems". It leaks some trans fluid into hydraulic sump and occasionally loses prime/gets airbound. But I'll also tell you it's been like this for 20 years and it still lifts heavy loads like new and they don't creep down with engine off.

One thing I have noticed, and maybe someone else can explain why this is so, it rarely, if ever, loses the prime if I make sure to park it with the lift arms all the way down (ie. not attached to an implement where the arms are parallel to the ground. If you're leaving it parked for extended periods attached to the chipper that could be aggravating the situation. I've also never had to loosen the plug to get it pumping again, I just let it run with the lift arms fully lowered (not attached to an implement) and the 3-pt control in the fully raised position; it usually picks up in 10-15 minutes.

Using the UTF oil in the trans or differential will make any leaks a lot worse. I run 80W-90 in those and so far no problems with hydraulic in 20 years lifting heavy implements, and I'm sure some mixing is going on. Once or twice every 50 hours or so I add some gear oil to the trans to bring it up to level. I know some is going into the hydraulic because it's high on the dipstick, but hard to say how much since the trans has a front seal leak as well.

As an experiment I think it would be worth your while to try parking it with the lift arms all the way down and see if the "problem" goes away. Then you will have to decide how much you want to dig into it.

You've also got the lines running internally from the pump manifold thru the trans compartment. I've heard you can get leaks there as well, so maybe keeping the lift arms down in storage keeps air from getting in via the control valve; I don't really know, can only relate my experiences. Maybe one of the resident board experts will chime in on this.

 

[bobsphotos]

Thanks for the advice. What oil do you run in the Hyd reservoir?
Bob W

 

[downslope]

Thanks for the advice. What oil do you run in the Hyd reservoir?
Bob W

I started like you with Ford/NH 134 type UTF in the hydraulics. Later I might have switched to 80W straight mineral oil like used in N-series Fords available from NAPA PN 65-205 , and also a product called Kentran 80 which has some additives. MF 1103 oil from Agco is also an 80W mineral oil.

If I were you I'd just stay with the UTF in the hyd sump since it's gonna mix anyways if you decide to change the trans to 80W-90 unless you fix the leak. At one time I actually siphoned some of the oil out of the hyd and poured it back in the trans. It can eventually get so full that it will start coming out of the dipstick. When I top up the trans I've been using regular GL5 hypoid oil.

Is the hydraulics strong when it's working? Lifts the chipper OK? Will it stay up for a while with the engine off?

If you can solve the problem of it losing prime, or at least live with it somehow I think you'll be OK.

 

[Soundguy]

position of the lift arms has -000000- to do witht he pump loosing prime.

the pump looses prime for 2 main reasons.

1, bad orings on the plumbing

2, bad shaft seal in the pump

1 is cheap and easy to check. 2 is more involved to fix, and requires some special tools if you really want to rebuild the pump completely.

if 1 doesn't fix it, and it otherwise runs fine all day and only needs to be bleed every couple days. and you don't want a full rebuild onthe pump.. then buy a 5$ petcock and screy it in place of the plug, giver her a turn open while cranking when it bubbles, close it and go.

As for a trans overfilling.. that is a perforated high pressure line that runs thru the trans.

it is a bit fo a task getting proper stepped tubes made.. but it can be done. otherwise you sleeve the perfed tube with soemthing like 10mm tubing and lots of epoxy.

if it's a small pinhole... the sleeving may well be the fix for the next 2 decades..e tc.

 

[bobsphotos]

When the 3 pt works, it works fine, and it will keep the implement raised for a long time. I will have to raise it and check it for leakdown.
Thanks,
Bob W

 

[bobsphotos]

position of the lift arms has -000000- to do witht he pump loosing prime.

the pump looses prime for 2 main reasons.

1, bad orings on the plumbing

2, bad shaft seal in the pump

1 is cheap and easy to check. 2 is more involved to fix, and requires some special tools if you really want to rebuild the pump completely.

if 1 doesn't fix it, and it otherwise runs fine all day and only needs to be bleed every couple days. and you don't want a full rebuild onthe pump.. then buy a 5$ petcock and screy it in place of the plug, giver her a turn open while cranking when it bubbles, close it and go.

As for a trans overfilling.. that is a perforated high pressure line that runs thru the trans.

it is a bit fo a task getting proper stepped tubes made.. but it can be done. otherwise you sleeve the perfed tube with soemthing like 10mm tubing and lots of epoxy.

if it's a small pinhole... the sleeving may well be the fix for the next 2 decades..e tc.

When you have time, could you elaborate a little on how to do #1.
Thanks,
Bob

 

[Soundguy]

if you look at the pump, there is a plumbing manifold that goes from there to the trans front face. that's where it joins the tubes that run thru the trans to the diffy... on either side of the plumbing manifold are the oring spots. at least one is a flat faced oring that i hav enot had good luck using round profile orings for.. instead.. get the cnh oring.

 

[downslope]

position of the lift arms has -000000- to do witht he pump loosing prime.
...
As for a trans overfilling.. that is a perforated high pressure line that runs thru the trans.

Thanks for the info about the pump and tube repairs. As far as overfilling, I think he was talking about the hyd reservoir not the trans getting overfull; would this most likely be a trans seal leak or can the tubes/o-ring failures cause an overfull hydraulic sump? Are there o-rings between the compartments too?

Yeah, I don't understand the thing about the lift arm position but it's pretty consistent on my tractor, if I leave it parked with the arms down it doesn't lose prime. If you think about it, what is different when the lift arms are left partially raised because they are attached to something: (1) the lift piston is in a different place in the bore and (2) the control valve linkage is positioned different. Maybe one of these combined with a plumbing or seal problem would let it lose prime in a shorter period of time, ie. provide a vent path for air to get in. I will defer to your Ford knowledge if I ever try to fix mine but in general it works OK 100 hours/year.

 

[Soundguy]

Thanks for the info about the pump and tube repairs. As far as overfilling, I think he was talking about the hyd reservoir not the trans getting overfull; would this most likely be a trans seal leak or can the tubes/o-ring failures cause an overfull hydraulic sump? Are there o-rings between the compartments too?

Yeah, I don't understand the thing about the lift arm position but it's pretty consistent on my tractor, if I leave it parked with the arms down it doesn't lose prime. If you think about it, what is different when the lift arms are left partially raised because they are attached to something: (1) the lift piston is in a different place in the bore and (2) the control valve linkage is positioned different. Maybe one of these combined with a plumbing or seal problem would let it lose prime in a shorter period of time, ie. provide a vent path for air to get in. I will defer to your Ford knowledge if I ever try to fix mine but in general it works OK 100 hours/year.

Well.. the piston, arms and unloader valve are all in the hyd TOP COVER.. the pump is bolted tot he side of the engine, and has a suction and high pressur eline to it. I'll stick to the opinion that lift position has no bearing on a pump loosing prime. Once the lift is lifted to a place where you want it, the unloader valve 'unloads' the system dumping it to sump just like it does with the lift arms down. thus.. the unloader valve should be in the unloading position at both times.. so that punches some holes in the theory right there.

If trans looses oil and hyds overfill, t is the suckion line that is perforated, sucking trans dry, overfilling hyds. VS trans overfilling, sucking hyds dry beaing a perforated high pressure line.