M4900 Hydraulic Problems. Power steering, PTO are OK. Everything else weak

[TheOldHokie]

Yes, nothing comes out when I do not pull the valve for the loader when I pull the valve fluid comes out of the hose
[/QUOTE]
Lets recap

1. You have flow to the base end of the cylinder but no lift.
2. There is no oil coming out the rod end of the cylinder.

Sounds like no pressure but other functions work. Very odd. Do you have a hydraulic pressure gauge? 3000 - 5000 PSI?

Dan

 

[ronv23]

I have one coming Monday. What would you like me to check. I don’t understand how it’s able to go up and down with nothing on it ?

 

[TheOldHokie]

Lets recap

1. You have flow to the base end of tye cylinder but no lift.
2. There is no oil coming out the rod end of the cylinder.

Sounds like no pressure but other functions work. Very odd. Do you have a hydraulic pressure gauge? 3000 - 5000 PSI?

Dan

I have one coming Monday. What would you like me to check. I don’t understand how it’s able to go up and down with nothing on it ?
[/QUOTE]
Low pressure would do that but you say all the other things work.

When you get your gauge hook it to that base end hose and see what the pressure is when you pull the lever.

Dan

 

[ronv23]

all lift functions are nonexistent at an idle

 

[TheOldHokie]

all lift functions are nonexistent at an idle

Lets mske this real explicit.

Will the 3pt lift a heavy implement?

Dan

 

[ronv23]

it has a post hole digger on it I will double check what it does tomorrow. I believe it isn’t as strong at an idle. Are there any valves or solenoids that I need to check?

 

[ronv23]

so I put the pressure gauge on the retract side for the lift cylinders and 0 psi.
Had a buddy stand on 3pt attachment and it would not go up. If I rev the tractor it will pick him up

 

[TheOldHokie]

so I put the pressure gauge on the retract side for the lift cylinders and 0 psi.
Had a buddy stand on 3pt attachment and it would not go up. If I rev the tractor it will pick him up

So you have PS but no loader or 3pt.

Thats a different animal and we start with the basics - pressure test at the pump. Do you know how to do that?

Dan

 

[ronv23]

no I do not. I was going to test scv pressure.

 

[TheOldHokie]

no I do not. I was going to test scv pressure.

Thats not going to tell you anything helpful. You need to get a grasp of how the hydraulics work.

Pressure starts at the pump and is passed to the loader, then the AUX valve, and finally the 3pt. If there is no pressure at the loader its not going to magically reappear someplace down stream.

Dan

 

[ronv23]

Would the input hose to the loader valve be a good place to start?

 

[TheOldHokie]

Would the input hose to the loader valve be a good place to start?

Yes but first you need to verify there is a pressure relief on the pump supply side. I dont know the details of the loader plumbing on the M4900. I would have to double check to be sure thats safe to do.

Dan

 

[ronv23]

It has an in and out labeled and then it has a third hose that I would think is a return

 

[TheOldHokie]

It has an in and out labeled and then it has a third hose that I would think is a return

Yes but is there a pressure relief on the tractor side of the IN hose. In most cases the answer is yes but I dont want to tell you to do something that will kull the pump. I am looking at the WSM right now. Post a picture of the tractor side connection of the IN hose so I can confirm we are on the same page.

Dan

 

[TheOldHokie]

Yes but is there a pressure relief on the tractor side of the IN hose. In most cases the answer is yes but I dont want to tell you to do something that will kull the pump. I am looking at the WSM right now. Post a picture of the tractor side connection of the IN hose so I can confirm we are on the same page.

Dan

WSM says there is a main system relief between the pump and outlet block which is located on the AUX valve housing. Is that where your loader is connected?

Dan

 

[ronv23]

yes supplyhoses goes towards the rear axle

 

[TheOldHokie]

yes supplyhoses goes towards the rear axle

Cant tell where the loader hoses connect to the tractor but the shop manual is pretty clear on the relief. Connect your gauge to the IN hose on the loader valve. You should see 2000+ PSI.

Dan

 

[ronv23]

To clarify. Connect gauge to inlet supply hose on loader valve? Circled are in and out hoses to loader valve

 

[TheOldHokie]

To clarify. Connect gauge to inlet supply hose on loader valve? Circled are in and out hoses to loader valve

Yes. To be explicit

1. Bring tractor to operating temperature and turn if off.
2. Disconnect hose at IN on loader valve and connect a 3000 PSI gauge to the hose.
3. Start tractor and immediately record pressure at idle RPM. Increase RPM to max engine speed and record pressure again.
4. Turn rngine off and reconnect hose to loader valve. Do not operate tractor with gauge connected for any longer than needed to record pressures.

 

[ronv23]

gauge doesn’t come off zero
Is how I’m testing it fine? Or does it need to flow thru