5000 lift issues

My friend has a 74 or 75 model 5000. He was having some
issues with the lift not raising when fluid got hot. We replaced
the hydraulic pump as well as the input strainer and it lasted a
little longer before showing issues but still has problems. He is
using a 6 bush hog and everything works fine when cold.
After the oil heats up, it will not lift the bush hog. Any
suggestions on what , or how, to check next?? Thanks
 
Time to pull the lift and replace all seals including the piston ring and leather washer. Oil is getting by somewhere when the oil thins after system heats up.
 
When it gets hot, does it stop working completely, or does it still at least try? In other words, does it gradually slow down and stop lifting, or is it like someone flipped an on/off switch?
 
He just called and said it quit. I have to find out if it quit completely or just got very weak? I remember on the older Fergusons you could remove one of the side covers and actually see where the worst oil leaks were at the top cover. The side covers on the Ford seam to be a lot lower so Im not sure if I could remove the left side cover and actually run the tractor? Or would it be best to just pull the top cover and start replacing stuff?? I am aware of the piston rings but not real sure about the leather ring or how many o rings we may need to get either??
 
If it gets weaker gradually as the oil heats up, you likely have a worn pump and/or internal leakage. If it works one moment and not the next you likely have a sticking unload valve.
 
It shouldnt be the pump as I just replaced it this past week with a new one. I will talk to him tomorrow at work and find out exactly how it acts when he stated it quit. I wouldnt doubt some internal leaks and Im not sure about the unloading valve. Is it possible to test or check it somehow?
 
Here is what I have found out. The lift never completely quit. After getting hot, the lift struggles to lift the bush hog completely. He said it was definitely better than before we changed the pump and strainer so there was some wear there. He said the pto performed fine so its getting plenty of pressure to keep it engaged. He also said when he got back on the highway and took off, there was some type of deep squealing type noise that sounded like it come from the rear end and tractor felt like the dif lock went in and out for some reason? No idea if hydraulics have anything to do with the rear end locking or not??
 
With cold oil, lift the bush hog all the way up and shut off the engine. Time how long it takes for the bush hog to touch the ground. Then repeat the test, except this time pull out the ASC knob immediately after you shut off the engine. The ASC knob is black, on the RH side of the lift cover towards the front. It moves in and out horizontally. Post back with the results of these two tests. Make sure you push the ASC knob back in after your test.
 
Had him go home after work and check. The results were it took about 25 seconds with the knob in,,,,, about 13 seconds with it pulled out. Not 100% sure of the purpose of the valve (maybe someone could educate us on that as well) but definitely made it drop quicker when engaged
 
That makes no sense. Pulling the knob out should have slowed it down or else made no change. I suspect that the knob didn't get pulled all the way out. I just checked my 5000, the knob has slightly less than one inch of travel (7/8 to be exact). Have him run the test again and make sure the knob comes out 7/8 inch.
 
He is pretty sure it was out all the way. It was 25 and 13 minutes instead of seconds. I misunderstood his text. He also said with the valve out, there was a slight clicking noise inside as it was dropping.
 
So to clarify, is it 25 seconds or 25 minutes for the first test? I need to be crystal clear on this, because if you maintain that it's 25 minutes and 13 minutes, that makes zero sense. As I said in my last post, pulling out the ASC valve should either slow it down or make no change.
 
Take a look at the pictures below and you'll understand why I'm struggling with your numbers. By pulling the ASC valve out (note that it's called the auxiliary service selector valve in the pics), you can clearly see that the lift cylinder is isolated when the valve is pulled out (lower of the two images). Everything that is pressurized with the valve pulled out is also pressurized with the valve pushed in, so by my way of thinking, when you pull the valve out the leakage should either be the same or slow way down, depending on the origin of the leak.

For example, if the problem was a bad lift cylinder seal, pulling the ASC valve out would have no effect. Conversely, if the problem was in the control valve area, pulling the ASC valve out should decrease the leakage dramatically.

I hope these pics clearly illustrate my quandary with your numbers here.
cvphoto104289.jpg
 
It looks like to me the valve should shut complete oil flow off to the lift cylinder which in turn should slow the drift down. Im thinking we may have either a problem with the ASC valve. This is almost the only possible thing that could make the lift drift down quicker with the valve opened and the lift cylinder blocked off??
 
That's possible, but not likely. The ASC valve is never used by anyone I know, so how could it wear?

What you could do is unscrew the black knob from the valve and peer inside with a flashlight while the lift is up in the air. If you have a noticeable leak from the valve you should be able to see it through the hole.
 
I told him I would bring my inspection camera Thursday and try to enter through the fill hole in the top of the rear end and hopefully I can see oil pouring down somewhere?? Never tried that with a Ford but years ago we would remove the side covers on MF and could see exactly what was leaking. Just not sure if there is enough room for the camera to work without getting covered in oil?? I will update what I find then with your suggestion as well.
 
Doubt you'd see much going through the oil fill hole. Your best bet would be looking through the large 4-bolt cover plate on the LH side by the step. Drain a couple gallons of oil first or else park it on an incline with the LH side high.
 
I took the 4 bolt cover off this afternoon. There was oil running down from several places but I couldnt really identify exactly where. There was a tremendous flow coming out of the small valve on the bottom of the return strainer. Not sure if that is right or not?? I pulled the lift top and replaced the piston rings, honed the cylinder, and replaced all the mounting orings. We let it run 20-30 minutes and it still seems to get weak the hotter it got. It got where it didnt want to lift at idle. You can rev a few hundred rpms and it would go on up. He is going to mow a few acres tomorrow and see if its actually any better when it gets hot.
 
The tremendous flow was return oil going to the return filter, which is normal. As for getting better when it gets hot, don't count on it. It's usually the other way around.

I once had a similar problem on a similar tractor. I finally located the leak by hoisting the cover in the air and plumbing oil to it from another tractor remote to see the leak.
 
I didnt mean I thought it would get better than current, just better than last week when it would only raise with throttle wide open. I felt there would be some oil coming back through the return, but was hoping for some valve troubles or something similar causing it to be so much? Maybe I should run it again with the side cover off and see if I could identify leaks? How did you adapt the oil from tractor #2 to the lift top in your testing method? He actually owns a 2nd 5000, its just a flat deck style tractor that I could possibly use for supply if I end up having to go to that extreme. Thanks for all your advice so far. As I stated earlier, I have a fair amount of experience with the MF lifts but this Ford has been a real learning experience!
 
Take a close look at the images I posted on Oct 12. You'll notice at the very top of either image the word check valve. Immediately to the left of that word you'll see a plug next to it that's not labeled. If you look close, that passageway gives you access to the lift cylinder and safety valve when the ASC valve is pulled out, and then the control valve is added in when the ASC valve is pushed in. This is why I can't see how it's possible for the drop rate to increase when the valve is pulled out.

With a long hose and the proper fittings, connect that port on the lift cover to the remote valve of another tractor to pressurize the various passageways, again depending on the position of the ASC valve. With the lift cover hanging in the air, you can easily see where the leaks are.
 

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