I'm really struggling with this issue. I'm by no means a hydraulic expert at all and am struggling to diagnose what the issue is. I don't want to throw parts at it but just don't know where to start. I have a very well used 410b that I believe the hydraulic pump is cavitating. When idling the pump is making a constant loping noise. When I run any of the functions(loader/backhoe) the noise.goes away while operating that function. The oil in the transmission also gets full of small bubbles. Here is what I've done so far. I'm checked the pump screen, replaced the suction hose from the trans sump to the pipe that feeds the charge pump and I've changed the filter and the oil twice. I feel like it's some sort of faulty relief valve when the tractor is just idling but I may be way off track I don't have much experience with hydraulics on heavy equipment. The power to the hoe and loader still seems adequate. I can lift the tractor up with the loader or the backhoe so I feel like it's not a pump problem. Any advice on how to proceed would be very much appreciated. Thanks in advance.
Did the noise just start happening or has it been there a while? Some chatter from those pumps is normal, but without being there to hear it, don't know if it is or not. Has the pump coupler between the engine and the pump been checked? If the rubber damper disintegrated or is damaged you would have metal to metal contact creating noise that may go away under load. Has the pump charge and standby pressures been checked? I would suggest getting yourself the tech manual TM1468.
The noise pattern could be entirely normal for a worn old backhoe, even normal when it came new. Sometimes you won't notice a small noise for the first year you have a machine, but once you're "one with the machine" then you start to notice the little quirks. So that system idles at full pressure, called standby pressure, that's the pressure that shuts off the pump flow, so that high pressure with no load will make a different noise as the pump turns on and off to maintain that high pressure. Once you open a valve, the pressure drops, and the pump maintains constant flow until the valve closes, or the cylinder stops, then it will return to standby. You should notice the engine has no load at standby pressure, and has more load when you operate the hydraulics. Then if you stall the dipper for instance, the engine will operate the same as if no valve was operated, the engine will have no load. All of that is normal operation. If there is excessive loping at idle from the hydraulic pump, then you might have a larger than normal leakage in the hydraulics, or worn control valve in the pump? Leakage will make heat, so you could start it up some cold morning when everything is coated in frost or dew, and see what melts and steams first. Obviously the muffler will melt first, then the engine and hydraulic pump, then the loader or backhoe or priority valve or brake or steering will melt. If one of those melts quickly and the rest take much longer, that MIGHT suggest a problem.
Ok, so I have the tech manual, I am trying to figure out what fittings I need to check the standby pressure. Once I have that info I will report back. The problem I'm seeing is the oil is very aerated when I pull the dipstick. I assume the loping noise and the aeration are related. The bulk of the noise seems like it's coming from the priority valve. I can hear it at the pump but it's not as loud there. Once other thing I noticed, not sure if it is related, I counted the number of turns on the manual stoke valve so I could put it back where it was and I closed it while the tractor was running and the noise was gone, but I have no hydraulic control when I do that. Thanks again
I might be totally off but I feel like at standby it's building pressure and dumping it over and over. Like a bad relief valve or something. Again I don't have a lot of experience with heavy equipment hydraulics.
The fittings needed should be in the manual, on the page that describes testing the charge pressure and standby pressure. It will look something like: a. re49587394857390487 pressure gauge (0-200bar) b. x3498w359087298 hose..... c. 9/16x32 ORFS x 3/32 JIC adapter d... You only need the thread size on the pump, probably ORFS, and get the rest of your stuff to connect with the right threads. And two gauges in the correct pressure range, one high pressure gauge can probably do it close enough. Yes, it could be building over and over again, it should not do that. There is a pressure relief valve in the priority valve, I think. It should NOT ordinarily relieve. It will warm up the return hose quicker than the other valves if it is relieving when it shouldn't be. The standby pressure test may show what is happening, then we can figure out why. The destroke valve shuts the pump off, so that is expected when you use the manual destroke valve.
Ok, so I did a standby test. The pictures in the downloaded manual weren't real clear. I think I was supposed to use the top port on the valve body. I ran the tractor for a while and then tested it it it was bouncing back and forth between 1450 and 1600 psi. The bounce was equal to the loping noise. Engine rpm didn't change the standby pressure significantly, other than the bounce on the gauge got faster.
Ok so I need to grab another gauge to check charge pump pressure. I'm starting to wonder if I have a problem with the charge pump or the relief valve in the filter housing. Does anyone know how to check charge pump flow without having a flow meter?
is hydraulic fluid too thick .. does suction line have a leak thats hard to detect ...
Sorry, I saw this and didn't respond till now. The standby pressure bouncing and that low of a pressure is a pretty good sign what is wrong. not that I can tell what exactly, but you definitely have a problem, this is not just the normal sound and operation. I'd be very curious what the standby pressure does when somebody operates the backhoe, or loader if you have a long enough hose to see the gauge safely. Dig the backhoe into the dirt and stall the stick function and see if it lopes the same way, or what? That would be system operating pressure you're measuring, same port, just operating, not standby. Or you could try the heat test. If it comfortably starts at freezing, then start it up some morning and see what melts first. As far as I know, you either have a pump problem or a relief valve problem in the priority valve. Investigate the priority valve in your manual, they're basically a manifold that splits the hydraulic pump flow to the steering, brakes, loader and backhoe valves. Plus a relief valve that will return oil to the reservoir, and the "priority" valve shuts off the loader valve if pressure is lower than a certain pressure. Come to think of it, a leaking loader valve could do what you're describing possibly? I don't think you have a charge pump issue. Everything I've read says they are very simple and durable. Check the pressure, if you're still worried, you could run it into a clean bucket and time the flow. It's a lower flow than the hydraulic pump, because the return from loader and backhoe are fed back into the hydraulic pump, the charge pump only has to keep the system up to pressure and provide transmission cooling, lube etc. NOT the full flow of the hydraulic pump. A charge pump problem is typically a hydraulic system leak, not a problem with the actual charge pump.
sorry wrong post
Ok so I got another gauge and checked the charge pump pressure, it was bouncing about 5 psi with the lope of the pump but it was dead nuts at 100psi where the manual says it's supposed.to be. The standby pressure is low according to the specs it should be around 2500 psi. As far was what happens when I operate the hydraulics the noise.stops the pressure drops slightly but does not bounce. I was alone so I couldn't stall the hoe into the ground while looking at the gauge, I just reached over and operated the loader while looking at the gauge. I can try stalling the hydraulics tomorrow. The bulk of the noise seems to be coming from the priority valve and possibly the loader valve it's real hard to tell. Thanks again for all the help.
Well I had a few minutes yesterday to pull a relief valve. I removed one of the circuit relief valves on the loader. I attached a photo of what I found. It appeared as though part of a rag had been sucked up into the valve. I was able to disassemble the valve and clean it, and get it reinstalled. Still making the same noise/symptoms but just worried what else I'm going to find as I pull relief valves. Hope to remove priority valve relief valve and other loader circuit relief valve this evening.
So I did check the screen last year before other stuff came up and I wasn't able to work on the backhoe. Unfortunately I kinda mangled it up when I was removing it so I didn't put it back in. I do have the screen on order to replace it. So as of right now there is no screen. I'm going to try and pull the relief valve on the priority valve tonight. I'm worried that that valve is gummed up with stuff and I'm going to have to pull the whole valve and rebuild it.
Ok so now I'm struggling here a little bit. I can't find the relief valve on my priority valve. Where the drawing shows it should be located there is a hose barb that has a short length of hose that goes to the transmission. The drawings in the tech manual and the parts lookup page aren't really clear. I don't know if the hose barb is supposed to thread into the relief valve, if that's the case then the relief valve is missing. Thank you all for the help.
The relief on the priority valve does not normally open. It is there for pressure spikes. The stroke control valve on the pump controls system pressure. With that being said it is possible debris got stuck in the relief during a pressure spike event.
This may sound like a stupid question but is there a special wrench or socket for removing these relief valves? When. I pulled one with better access I was able to get an adjustable wrench on two of the flats to remove it. This one is recessed a little and I can't get an adjustable wrench in there. The valve has long and short flats and a couple of rounded corners on it and sockets don't seem to fit it. Only socket I didn't have was a 31 mm. 30 was too small, 32 was too big, 1-1/4 was too big 1-3/16 was too small. Thanks.
Are you sure that crap in the system is not part of a filter that has ruptured internally? Maybe you need to remove the hyd filter and check to see if it is intact.
Filters have been changed, oils been changed suction screen in sump has been cleaned, priority valve screen has been removed but I damaged it on removal,need to replace that screen, filters looked fine when replaced.
So I removed the relief valve from the priority valve and everything looks fine. Now I'm wondering if I should be looking harder at the pump. The standby pressure is low. And it's pulsating, I'm not sure what I should be looking at with the pump to help make the decision if it needs to be rebuilt
If that's the old radial pump, they have a lot of areas to check such as worn cam needle bearings, worn pistons, worn or broken inlet and outlet valves and inlet or outlet valves loose in the housing
Pressure control valve in the pump. Check that before you pull the pump apart. I believe it's removable without doing anything else to the pump.
On an old radial pump, if you mess with the stroke control(pressure control) valve and get the pressure too high, you can blow an outlet valve plug out of the housing, especially if the threads are weak to start with. I had it happen 40years ago. If you take it apart, back off the pressure setting and only adjust it using a pressure gauge. About 2250psi if i recall correctly