1974 (?) Ford 5000 Diesel Losing hydraulic pressure once it warms up

[RobbinsFF]

Hi all, I recently bought a Ford 5000 diesel and have noticed that when I start it up cold, there is plenty of strength to lift a bush hog. However, about 45 minutes into a session I seem to lose all power. I put deadheaded a gauge on it cold and got about 2200 lbs and then did that again at 15, 30 minutes and it stayed pretty strong at 15 but was weaker at 30 minutes and then about 1000 lbs at 45 minutes. Increasing RPM had no impact so I'm thinking it's not the pump but more likely a pressure relief valve. I believe the valve is located under the drivers side foot rest under the pump. Wanted to get some feedback from the experts before digging too much deeper.

Thanks,
Thomas

 

[Harry in Ky]

We'll see what the experts come up with, but in my experience relief valves don't fade away after an hour's run time then come back to life the next day with cool oil only to fail again again later. That's what tired pumps do. If you feel the need to remove and inspect said relief, then by all means go for it. Let's see what that gains you.

 

[TN 2N]

My 5000 did the same thing but got progressively worse. Shut off for a few minutes and it would work a little longer. Suction screen was almost stopped up with fine black particles. New screen and new oil fixed the problem.

 

[m16ty]

When your tractor gets hot the oil gets thin. Seems the tractor has no trouble pumping the thick oil but you have an internal leak when the oil gets thin.
Could be a leaky relief, could be bypassing in the valve, or it could a worn pump. I’m going to say your pump is almost shot, but it would probably be wise to check the other parts of the system first.

 

[UncleTom]

Please give us follow up.

 

[RobbinsFF]

m16ty ... that was my thinking as well. Is that screen also near the bottom of the pump? What is best way to access ... Take the top of the unit?

I'm sure there is a lot of sludge in there given the age and just want to make sure I check/clean everything before going the new pump route.

 

[sotxbill]

Most times I have seen this, it was a worn out hydraulic pump... simi good pressure at startup, but guickly drops as fluid warms up a bit... ie 1700lbs at start, then slowly drops to 1200lbs on a Ford 5000. Another was already at 1200lbs give or take and dropped to 700lbs ... These tractors were fixed with a pump replacement. Did have a dual pump 5610 that has stopped up filters that horrible low frontend loader times but had great deadhead pressures... but it had horrible growth in the hyd fluid that could fill the filters up with a grey slime in a matter of a couple of hours... Good static pressure, but low flow...

 

[TN 2N]

m16ty ... that was my thinking as well. Is that screen also near the bottom of the pump? What is best way to access ... Take the top of the unit?

I'm sure there is a lot of sludge in there given the age and just want to make sure I check/clean everything before going the new pump route.

Access through the pump opening on the right side.