How to test hydraulic pressure

[DIXIEDOG]

I purchased a 5000 psi hydraulic pressure gauge to test my hydraulic pressure on my International 2544 that I'm having a loader not lifting problem with. Do I just unhook the lift hose from my loader joystick and replace the hose with the gage and test pressure? I also would like to test the pressure out of my flow divider block as well, the divider block has a relief valve in it so do I have to put a tee in or can I just cap off the line and test the pressure? I'm a hydraulic idiot so please excuse the remedial hydraulic questions

 

[kennyd]

To test the PRV (pressure relief valve) pressure, you need to "deadhead" the hydraulic system...So like you said-disconnect one of the lines going to your loader and plug the gauge in, then operate the joystick to send pressure to that port. The reading on the gauge is what the PRV is set to. Not sure about the "divider block" but the theory is the same, just be sure to only deadhead the system for a few seconds at a time.

 

[J_J]

You need to know what your max/designed pump pressure is, then you can use that as a reference for all other measurements.

What Kenny said, plus it would be a good idea to put a needle valve down stream of the pressure gage to put some load on the pump when necessary. Just idling, the pump is not doing much work, and if you read the gage, you could read different pressures depending on what you are doing. If you raise an empty bucket, you will see some pressure, and when you hold it at the end of travel, then the pressure builds up to the relief pressure. To test pump pressure, put the gage before any device that is controlling pressure, but this is difficult as Kenny said, because, if you totally block off the pump while it is running, then something is going to break/burst, and it will be the weakest part of the system. When a pump splits open, or cracks, you can almost bet that something/somebody caused a deadhead. If you plumb a tee with male Quick Disconnects, at several locations around the tractor, and then put a female Quick Disconnect on the gage, and you can test your pressures at any time. Some QD's can be attached with pressure in the lines. You can leave the gage in place to monitor the pressure at any location, by using a 6 ft hose set up. Using the gage, you can trouble shoot the hyd system.

Just removing the hose and putting the gage in the same spot is not a good idea. What if the relief is stuck, then the pressure will build up until something breaks. Put the tee on the front side of the valve to see what is being supplied to the divider, and then put it after to see what is being divided. Now, even though some of the fluid is being divided, you could read any pressure, depends what is being used downstream. Expect to see spikes that may go above pump pressure, caused by sudden movement.

 

[DIXIEDOG]

So if I plumb T fittings in-line I will be able to test pressure at the T. I think I'm losing my pressure at the rear block, when I grab my aux. hydraulic line it has a lot of vibration so it feels like it's pumping alot but when I grab either hose after the block I feel very little vibration in the line. So if I'm understanding correctly I can put a T in before my rear block to test the input pressure at that block then install a T after the rear block to test output and I can tell if that is where my pressure drop is?


Also when I unhook the loader line to "deadhead" the system do I need to do anything to the unhooked hose or can it just be left open?

 

[J_J]

So if I plumb T fittings in-line I will be able to test pressure at the T. I think I'm losing my pressure at the rear block, when I grab my aux. hydraulic line it has a lot of vibration so it feels like it's pumping alot but when I grab either hose after the block I feel very little vibration in the line. So if I'm understanding correctly I can put a T in before my rear block to test the input pressure at that block then install a T after the rear block to test output and I can tell if that is where my pressure drop is?


Also when I unhook the loader line to "deadhead" the system do I need to do anything to the unhooked hose or can it just be left open?

DIXIEDOG,

Install the tees wherever you want to test. You can do the tee thing one at a time with min parts, tees, and caps, with just a few fittings, but if you want to test in the long run, $75 in parts, QD's, tees, adapters.

Do not deadhead your system, you will be sorry. Also be careful on the QD, as they will cause a deadhead, depended where located. Deadhead is a term that is used mainly as a warning. In order to read or get a pressure, there has to be something in the path to block or use the fluid, such as a cylinder, motor, power steering, or just a valve to close down the line to a small orifice. However if you block it totally, something has to give, and it could be an expensive pump. If you have QD's, make sure they are working correctly. You may have a relief stuck open, divider valve, joystick or loader valve, etc. Does any other hyd function on the tractor work correctly?

On most of my equipment, with QD's, I plug the male into the female for several reasons, to make sure you don't have a deadhead, and to help keep them clean, etc.

I suspect your QD's are not passing fluid correctly, and the reliefs maybe working to relieve the pressure, because of a blockage, a malfunction QD.
Connect and reconnect them a couple of times. To really test the QD's would be to unscrew the QD going to the cyl, and plug it into the mate, and put the end in a clean bucket, and use the valve to apply fluid. If fluid flows, that set of QD's are good. Then check the others. Your divider valve might not be dividing , and the excess is being relieved back to tank.

 

[DIXIEDOG]

The power steering and the curl of the loader work correctly.

My tractor doesn't have quick connect fittings on it.

 

[kennyd]

The power steering and the curl of the loader work correctly.

My tractor doesn't have quick connect fittings on it.

So, what happens when you try the lift? Any movement at all? Does the engine bog down?

 

[kennyd]

You need to know what your max/designed pump pressure is, then you can use that as a reference for all other measurements.

What Kenny said, plus it would be a good idea to put a needle valve down stream of the pressure gage to put some load on the pump when necessary. Just idling, the pump is not doing much work, and if you read the gage, you could read different pressures depending on what you are doing. If you raise an empty bucket, you will see some pressure, and when you hold it at the end of travel, then the pressure builds up to the relief pressure. To test pump pressure, put the gage before any device that is controlling pressure, but this is difficult as Kenny said, because, if you totally block off the pump while it is running, then something is going to break/burst, and it will be the weakest part of the system. When a pump splits open, or cracks, you can almost bet that something/somebody caused a deadhead. If you plumb a tee with male Quick Disconnects, at several locations around the tractor, and then put a female Quick Disconnect on the gage, and you can test your pressures at any time. Some QD's can be attached with pressure in the lines. You can leave the gage in place to monitor the pressure at any location, by using a 6 ft hose set up. Using the gage, you can trouble shoot the hyd system.

Just removing the hose and putting the gage in the same spot is not a good idea. What if the relief is stuck, then the pressure will build up until something breaks. Put the tee on the front side of the valve to see what is being supplied to the divider, and then put it after to see what is being divided. Now, even though some of the fluid is being divided, you could read any pressure, depends what is being used downstream. Expect to see spikes that may go above pump pressure, caused by sudden movement.

DIXIEDOG,

Install the tees wherever you want to test. You can do the tee thing one at a time with min parts, tees, and caps, with just a few fittings, but if you want to test in the long run, $75 in parts, QD's, tees, adapters.

Do not deadhead your system, you will be sorry. Also be careful on the QD, as they will cause a deadhead, depended where located. Deadhead is a term that is used mainly as a warning. In order to read or get a pressure, there has to be something in the path to block or use the fluid, such as a cylinder, motor, power steering, or just a valve to close down the line to a small orifice. However if you block it totally, something has to give, and it could be an expensive pump. If you have QD's, make sure they are working correctly. You may have a relief stuck open, divider valve, joystick or loader valve, etc. Does any other hyd function on the tractor work correctly?

On most of my equipment, with QD's, I plug the male into the female for several reasons, to make sure you don't have a deadhead, and to help keep them clean, etc.

I suspect your QD's are not passing fluid correctly, and the reliefs maybe working to relieve the pressure, because of a blockage, a malfunction QD.
Connect and reconnect them a couple of times. To really test the QD's would be to unscrew the QD going to the cyl, and plug it into the mate, and put the end in a clean bucket, and use the valve to apply fluid. If fluid flows, that set of QD's are good. Then check the others. Your divider valve might not be dividing , and the excess is being relieved back to tank.

JJ,
I do not agree that deadheading the system is bad for a few seconds at a time-it happens quite frequently while using any function normally. That is the only way to test the PRV and see if the pump is reaching proper pressure. Sure, you can add T's all over the system to plug a gauge into...but you still need to deadhead the system to test it properly.

 

[J_J]

Kenny,

You, I, and a lot of others know this, but I think we are trying to help someone not quite familiar with hydraulics. If he damages something, he might just blame us for his lack of knowledge, and I was trying to avoid that. Instead of that groan/whine, when the relief kicks in, you might hear a pop, and fluid is all over the ground..

DIXIEDOG, Since you don't have QD's, forget all that. When you shift your joystick all the way fwd, do you hear a groan or squeal, like fluid rushing through a small orifice. You should hear this sound when you get to the end of travel of the cylinders, both ways. Did you say that the hose jerks/vibrates going to the valve?

 

[DIXIEDOG]

So, what happens when you try the lift? Any movement at all? Does the engine bog down?

I do get slow movement if I rev the engine up. The engine doesn't bog at all.


JJ I do get some vibration in the hose, it's not like the hose is jumping around though, it's when I gently squeeze on the rubber hose I can feel movement. As far as groan I don't get any.