I rebuilt the engine in my "new to me" Ford 4500 this summer and have been using it around my property ever since. Not knowing what to expect for digging power etc, I thought it was ok. The machine as not running when I got it. After some more research I decided to compare my machine to some published specs I had. The 740 FEL has a raised time to height of 4.7 seconds, mine takes about 15. That comparison got me to do some more research and saw that I should test the system relief pressure. Spec is 2200 psi @ 1700 RPM. Mine is 1700 psi and drops down to about 1500-1600 after a few seconds. I tried to increase the pressure as described in the manual and could only manage to get 1800 psi out of it before I ran out of adjustment on the adjusting screw. I suspect that I may have to R&R the system relief components in the control body. There is always a sound coming from it when operating any hydraulics, FEL or backhoe. My guess is that the pump is ok but without specialty flow test equipment I am going by gut. The next thing I can do is to disconnect the backhoe hydraulics (as if I were separating the backhoe from the tractor) and see how the FEL responds. I suspect that the FEL will be much stronger and faster. If so, I believe the pump will be fine but the control valve body will need some work. PS- Yes the hydraulic oil level is good, the filter is good and the screen in the nose tank is clean. There are no noise or vibrations that would indicate low flow. Any additional suggests?
Older hydraulic pump may just be more open as to tolerances, that will allow fluid bypass (known as slip)and drop head pressure which cannot in most instances be aided with relief valve adjustments. My old Allis loader has a weak pum, will dig just fine but won't always break out a considerable load in the bucket, I know it needs a pump.
I think you're on the right track. The fact that the pressure improved by adjusting the relief indicates that the pump may put out more pressure (the relief shouldn't be leaking at 1,700psi so adjusting it shouldn't increase the pressure). Disconnecting the backhoe valve sounds like a good next step. Also, you could look for hot spots with a pointer thermometer if you have one, or want to spend $20 on fleabay.
Does anyone know where the pressure port is on the 740 loader. Once the backhoe is bypassed I want to check the relief pressure is at the 1900 psi spec'd. Mine is the simple setup with no diverter valve our self leveling capabilities. Thanks!
If the unit cant hit 2000 with the relief cranked the pump is 90% of the time bad. Especially a backhoe with a gear pump
What you need to remember is pressure = power while flow = speed a wore out pump will will even build pressure yet it will not put out the required flow especially a older gear pump like that.
Ok, after visiting family for Christmas I had the chance to get back to the backhoe today. I bypassed the hydraulics as if detaching the backhoe attachment. The result was that the FEL was the only system being supplied power. How did it work? Lift to max height took about 6 seconds and is pretty close to the 4.7 second spec'd out. This was on a cold start situation as well. This is a major improvement over the 15 seconds I had been getting previously! Pretty much shows the pump is good and that there as an issue with the valve body in the hoe. Tried to just remove the system relief but couldn't get a good hold of it and didn't want to risk damage trying to unscrew it. At this point I am removing lines from the valve body to remove the whole thing. Once it's out I can take the next step. I do have a line on a used valve body from a member so one way or another I'll get it back up to full strength soon!
Got the valve body off and cleaned up the best I could. Brought it to a local guy with my diagrams in hand. He quickly determined that several of the o rings in the system relief were missing. He installed new ones and said I was good to go. I am going to try to get this put back together tomorrow so I can play this weekend. Wish me luck!
Good luck, and don't forget to back off the relief that you cranked down!
One step ahead of you, bud. It got cleaned up and reassembled with it cranked out. Not looking forward to putting it all back together outside in the cold tomorrow. Someday I'll build a nice shop with a radiant heat floor
Success! A few new o rings and pulling out a piece of debris from the valve body has fixed my hoe! The debris was a plastic dust cap trapped in the valve body somehow. Wonder how that got in there and how long it's been there. I still have to set the system relief pressure but it works great already!