Good morning all I have a question about a older ford 4500 backhoe. The hoe run good and loader bucket seems to be strong but the hoe part is weak. The bucket will not curl in if its too full and the lift will not come up as well when lifting. My question is can the pressure be turned up on the hoe itself. I seen the two acorn nut on the valve itself can I increase the pressure by turning them in??? Thanks for all imput.
Most of the 4500 had a 752 hoe on them I seem to think. Depending on how long you have owned this machine I would first change the filter in the hyd tank up front along with the strainer in the lower end. Is you hyd fluid milky in the tank? if so you also may want to change it out or at least let the machine settle and remove the drain plugs on the loader frame and bleed out some water every now and then. That being said with no history and without a flow test on the pump or a pressure check I would be careful to turn the main relief or circuit relief screws without installing a gauge and line in the test port at the rear valve. Your circuit reliefs are set at different pressures, your main relief on the backhoe is around 2200 psi I seem to think. It will not do you any good if the main pump cannot provide the flow and pressure needed for the hoe to make adjustments. Old and or missing o rings in the reliefs and worn seats inside the relief valves, cylinder packing, spool travel and linkage can also be a factor in the backhoe operation. Its been a while since working on a 4500, There are several on the form that will chime in, I think mitch may have some service book info. As always you can turn adjustment screws in but the outcome without gauges and correct pressure settings can be expensive and dangerous.
Hey Sheepfoot thanks for the reply. If I may let me tell you a little on history and what we have done here at the shop so far. I have owned it for about 8 months bought at an estate auction so really no history on it at all but tractor itself looks pretty worn. With that being said we removed the hyd. tank, cleaned the strainer in the bottom, replaced the filter, drained and replaced the fluid, ( a buddy of mine had a parts tractor ) so that were we got the other pump to replace, but still he hoe was weak. we replaced the pins and side plates at the valve, rebushed the rocker arms and all 6 leavers ( so no more slop ) and still weak. I guess I need to go about this the correct way and start with a pressure test and flow test so what is the best way to do that
It would be nice in a perfect world to have a hyd pump/cylinder shop that had a bench testing unit that could check the flow off the machine for your pump. I seem to think there is a fitting on the loader valve (fitting close by) to install a test hose with a 1/8 pipe thread, I would connect a hose with a 5000 psi gauge, start the engine, with it just over idle raise the loader all the way up and read the pressure. If the pressure moves quick read the pressure and make a note, next same test at just under full rpm and read the pressure, make a note. I am looking for the idle speed to max the pressure of what ever the loader relief is set at quick. If you do it at low idle and it reads 1ooo psi and then you do it at just below full and it read say 2500 psi I would think the pump has some wear issues. You may find someone close that has a portable flow rater that could check you pump. It 's hard to tell you where the problem is until a set of pressure test are done. The hoe could have the main relief set correct and the circuit relief for the boom up be the issue, same with the bucket curl. The main thing we don't want is to get the main relief to high, and a circuit relief setting to high causing the pump to split/hose busting/rods bent and packing blown. I am still looking for some info. What part of nc do you live.
Thanks again Sheep and in a perfect world i would not have bought a pos of a tractor LOL No its not that bad we have done quite a bit of work the it already and i am determined to get this thang to dig correctly. Actually im in this tractor with a friend so its not that bad. ill try to do some checks this weekend if I get a chance. I can post some pics of this beast if that would help i would like to check some numbers to see what year it was made. Im in lexington NC if you had an service manual you could share that would be great ( I have cash ) ??? lol I do appreciate all the help
4500 backhoe Here are a few pics of this beast where do I need to plumb in the guage at
and some more pics trying to find the age and any other spec. i may need for this ford
And one more
anybody out there lol??
Those things with the acorn nut on the end look like the relief valves. Take the whole thing out take it apart clean the sludge out of it replace any 0 rings and stick it back in. Under the acorn is the adjustment with a lock nut but I wouldn't mess with the pressure unless I had the proper gauges to set it to the correct pressure.
yeah i see there an adjustmet there but i was really woundering how to check the pressure correctly first be fore i start cranking on the pressure reliefs
I was waiting for a friend to call me back and haven't heard from him yet. Looking on the ford parts page the loader uses two pressure settings for the main relief, one is set at 1900 psi and the other is 2200 psi depending on the valve. I would get a tee fitting and hook it into the loader lift cylinder line to hook a gauge into. The parts did not show a fitting with a 1/8 pipe plug or test fitting drilled and taped into a fitting on the loader. It did show a fitting on the backhoe valve that may be the pressure testing for the main relief. I did find a operator manual in the shop that lists the 4500 hyd package, it lists the pump at 2200 rpm @1900 psi at 27.8 gpm, and at 2200 psi 27.4 gpm. In your 3rd pic the lower end section has the main relief across from the lever bended end. I think they have some portable flow raters at northern tool, that would handle your flow and pressure to check your pump. I will cost some bucks to get your adapter fittings and hoses made up, it's hard to spend that kind of dollars when you could buy a pump for less unless you did a lot of testing. More info coming.
so your saying the main relief is the center one? with the acorn nut? right any ways i was planning on removing the valve and taking it apart and replacing the orings and cleaning everything up anyways. But i wasnt going to screw the reliefs apart just clean and oring the hoe is basically the same with the old pump as well as the new one so I wouldnt think it could be 2 bad pumps but who knows but for now ill wait for more info iv got other things to fix on it any ways lol
Hey Harley, email me if you've still got my email, otherwise pm me yours and I'll send you the pressure test info one day this week. there is a procedure to turn one of the cylinders into a pressure amplifier to set the individual reliefs. It's not hard, just time consuming. If I remember right, the hoe pressure is higher than the loader, and it was common for the hoe to be weak, and the loader to be ok. I would start by checking the pressures, and go to a flow check if that doesn't work. you can get a cheap pressure guage that'll do fine for occasional use on the pressure washer parts aisle at Northern Tool, if there's one nearby.
did you get my email mitch?
I had a similar problem on my 4500. In the end the fix was to replace a few missing o rings. The pressure relief valve is located on the hoe hydraulic block. A quick pressure test will confirm if the relief is working or out of adjustment. If you don't have a gauge and want to get an idea if the rest of the hydraulic system is healthy, just disconnect the hoe from the hydraulics just like you were going to remove the whole hoe package from the tractor. I did this and was amazed at how fast the loader was! At that point I knew the problem was in the hydraulic block in the hoe. The missing o rings wouldn't allow pressure to build in the system and the pressure relief was never allowing pressure to build up
thats what im thinking too like i said in my earlier post i changed the pump out with another one but it the same way with both pumps (i wouldn't think 2 pumps would be bad) now where would you connect the pressure gauge to check psi? and which relief are you talking about the hoe block has 2 adjustments in the center of the block. do i unscrew the whole relief to dissemble it?
There is a square pipe plug on the bottom of the valve body. From the back of the machine it will be on the bottom of the valve body and to the far right. Remove the plug and screw in a gauge. I used a piece of hose long enough for me to read the gauge while operating the controls. The main system pressure relief is to the far right, as well. You should be able to see that it is adjustable and has a screw and lock nut to hold the setting. You can unscrew the whole valve pretty easily and check for scoring and o-ring condition.
Is this what im looking for?? lol and do i just replace the orings? an i missing a spring?
I AM missing a spring that might be the problem
where do i get one and im figuring 15 is the oring and im not sure what 16 is? all i have is the cup itself
where can i find number 12 and whats the part number
Find your nearest ford dealer or give messiks a call. The part number you are looking for 7707921 spring is $1.78 and showing a good number. Looks like your making head way on your issue, I still haven't had any luck with my friend that's working out of town, hope mitch was able to get you some info. If you go to the newhollandna const site, type in 753 and it should help you with some parts picks, then check the messiks site for numbers and sub numbers and prices. If you have the tag on the backhoe it should tell the model 752/753/755 etc. Hope this helps a little more.
Hey that's messicks spelled it wrong.
Thank you sheepfoot thats what i needed i got one coming in the mail NOW once i get the spring in place and back together ill try it but i probably need to check system pressure before I use it too much correct? If I take the square headed plug out and plumb in a gauge I should see around 2200 psi with the machine at full stroke am I right in that thinking?
That should be correct 2200psi on the main relief for the hoe. Once you reinstall the main relief, hook your gauge in (may want a 3000psi to start with or higher) use your backhoe boom up to read your pressure, then if needed loosen your acorn nut and locknut and adjust if needed. It would be nice to replace the o rings and backups on that main so you could set it and forget it. It will hopefully give you the answers you need to dig a little deeper and make some other adjustments.
yeah your right i want to replace all the orings if you had part numbers on those as well my oring assortment are too small in diameter i love to replase the orings on both the other two reliefs as well because of all the fluid loss when you remove them but i guess for now if i can get it to diggin ill be happy
Did you ever see a tag on the backhoe, may be on the tower or rt/lt side at the stab tube end. Really should try to find what size/ model it is.
any update?