How to test hydraulic pressure

DIXIEDOG · May 20, 2009

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 · May 20, 2009

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 · May 20, 2009

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 · May 20, 2009

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 · May 20, 2009

DIXIEDOG said:
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 · May 20, 2009

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

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

kennyd · May 20, 2009

DIXIEDOG said:
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 · May 20, 2009

J_J said:
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.

J_J said:
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 · May 20, 2009

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 · May 20, 2009

kennyd said:
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.

J_J · May 20, 2009

Your divider may not be dividing. Does your divider valve divide the fluid so some or most, or just how is it configured. One leg off the output may service the power steering, and the other leg may go to the loader valve. Does the power steering work better/faster than it was before. Some divider valves are equal in the output. Say you had 10 GPM going to the divider, then, 5 GPM would exit out each port of the valve. Some of them are unequal, in that one leg may only feed 3 GPM, and the other leg push out 7 GPM. Tee your gage in before the divider valve, and tell us the pressure. I am assuming that the fluid comes directly from the pump to the divider valve, and I believe you said it had a relief. There are several ways to trouble shoot systems, and that is to work from known good points, through to the stop point. The other way is to work backward to find the first good point.

SPYDERLK · May 20, 2009

kennyd said:
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.

That is not a deadhead if there is a functioning relief valve in the pressure circuit. If you dont have the relief you do have a deadhead. It will cause something to break instantly. The fluid must have a place to go or pressure immediately rises to failure.
larry

DIXIEDOG · May 20, 2009

J_J said:
Your divider may not be dividing. Does your divider valve divide the fluid so some or most, or just how is it configured. One leg off the output may service the power steering, and the other leg may go to the loader valve. Does the power steering work better/faster than it was before. Some divider valves are equal in the output. Say you had 10 GPM going to the divider, then, 5 GPM would exit out each port of the valve. Some of them are unequal, in that one leg may only feed 3 GPM, and the other leg push out 7 GPM. Tee your gage in before the divider valve, and tell us the pressure. I am assuming that the fluid comes directly from the pump to the divider valve, and I believe you said it had a relief. There are several ways to trouble shoot systems, and that is to work from known good points, through to the stop point. The other way is to work backward to find the first good point.

On my tractor the fluid goes direct from the pump to a divider valve. The pump is a 17 GPM pump and 3.5 is supposed to be dedicated to the power steering and the rest is supposed to go to my aux. line which runs to a rear divider block. My power steering didn't get any faster, I will need to pick up a T to hook up to my lines, right now I've only got the gauge and a bunch of thread adapters but not T. After I get the T and test the pressures I will post my results. Thanks for the help guys, I've done a lot of engine work over the years but I have no hydraulic experience....yet

kennyd · May 21, 2009

J_J said:
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..

Agreed. That is why I specified "just be sure to only deadhead the system for a few seconds at a time."

kennyd · May 21, 2009

SPYDERLK said:
That is not a deadhead if there is a functioning relief valve in the pressure circuit. If you dont have the relief you do have a deadhead. It will cause something to break instantly. The fluid must have a place to go or pressure immediately rises to failure.
larry

While "technically" you are correct...this is a accepted term used in the testing of a PRV. It's even mentioned in my service manual.

DIXIEDOG · Jun 14, 2009

Just an update. I was finally able to get all the fittings to test my hydraulic pressure and I had under 200lbs of pressure

Although my relief valve didn't look to be stuck open it must have been. I changed the relief valve and all is well for now

On a side note I think I got the world's oldest remaining new relief valve, it was still in an original International box

They had it so long that it wasn't in their computer system because they had it before they got the computers. Price was still the same $220 but at least my front end loader is working again

Thanks for the help guys, now I've gotta go finish moving my rocks

J_J · Jun 14, 2009

You paid how much for a relief valve? Can you post a picture, and perhaps a part number.

Is this similar to what you purchased, and installed, or did you purchase the divider block assembly with relief valve.

https://www.surpluscenter.com/item.asp?UID=2009061420490339&item=9-4351&catname=hydraulic

DIXIEDOG · Jun 15, 2009

It was this one. The one you linked was only 600 psi, mine is 1600psi. It was only the relief valve, no divider block. I wish parts for this were cheaper but I haven't found any cheaper ones yet

Case/IH part# 389033R92

J_J · Jun 15, 2009

DIXIEDOG said:
It was this one. The one you linked was only 600 psi, mine is 1600psi. It was only the relief valve, no divider block. I wish parts for this were cheaper but I haven't found any cheaper ones yet

Case/IH part# 389033R92

I just showed that picture for the style of relief valve. I knew your valve had a higher pressure. I don't know if you have to use a Case relief valve. It should cross to something else. Maybe Wayne can answer that one. about substitution.