I’ve got a six spline gear pump on the old Case. Now that I’ve replaced the valve, I can’t get any pressure from the pump. I’ve got great return flow up to the brand new oil filter, but out of the filter only about a tenth as much as going into it. My du-Al loader has a vertical tank which is full, and there’s a ball valve just before the filter that I use to check on the flow. My question is, does the pump suck fluid in from the bottom of the tank? I don’t see how the dribble it’s getting from gravity could be enough. The pump is about 20 years old but only has about 50 hours on it at most and was working when I replaced the valve. Any suggestions much appreciated.
No PTO pump pressure
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Leejohn
Elite Member
"brand new oil filter" There is where I would start.
Right. Carquest didn’t have the same 85551. Napa got me one they said swapped, a Napa # 1551. I’ll look online and see if I can check the numbers. But first I need to know for sure that the gravity flow into the filter is supposed to be about the same as the outlet side. Or what ratio is normal. I’m guessing the filter is slowing the flow by 90%. But if the pump is normally sucking maybe that filter is the right one. So that’s my questions. Is the filter normally reducing flow 90%, and does the pump suck fluid in
I think it’s air lock but won’t be able to bleed it until I get a 1” pipe T in the return port of the pump. I think the reason I’ve never had this problem before might be the cold weather. I’ve just done hydraulics in the summer. It’s a combination of things. I had the filler plug in the tank for one, causing air lock from above. and the hose goes uphill from filter to pump. I took every fitting apart and every hose off. When I opened the hose at the return I heard air coming out. But it’s not purging enough without a T.
KWentling
Veteran Member
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- Kubota BX22, Kubota ZD21, Kubota M7060
Pretty hard good advise with such little information, but I'll try. This is on 1957 Case tractor of unknown model. The pump might be a PTO pump? This pump draws form a reservoir on the loader? The valve was replaced for some reason? There should not be a filter between the reservoir and the pump suction. There ideally would be suction strainer in the tank that the suction hose attaches to. An alternative would be a Y strainer in the line. (If you truly have a hydraulic filter plumbed into the suction line, that line is probably collapsing.) The ball valve in that line would be fine. It would allow working the pump or line without draining the oil. The pressure line would go the the P port on the valve. The return line would go from the T port back to the reservoir and at some point between the valve and reservoir there would be a filter. Ideally the pump would be the lowest point of the system. The suction hose would all run down hill from the reservoir to the pump with no uphill humps to trap air. The fill cap on the reservoir should be vented. Hopefully your new valve has a pressure relief valve.
Of course it has a relief valve, it’s running a loader. The pump is almost the lowest point, it can’t be lower than the PTO shaft it’s on, and the tank is also the vertical post on the loader so it’s as high as it’s going to get, but it’s return port IS two inches lower than the pump and it works just fine. You call the return line a suction line accurately so why would the pump need to be lower than the tank return? The full cap should be vented as you say but it’s been unvented for the 25 years I’ve been using it.
Yes it’s a PTO pump, as I said, it’s a six spline gear pump so it’s a PTO pump, did you read my question?
What is your reason for not wanting a filter between the tank and the pump? It’s been there since I bought it 25 years ago. It’s not starving the pump and if it were, it wouldn’t hurt a thing, and I’d sure know about it.
My new Prince valve doesn’t have P or T ports. It’s got IN and OUT ports. It works great, I got it working today by cracking the pressure side of the pump for two seconds to purge the air and prime it.
BTW it wouldn’t make any sense to put the filter on the intake side of the tank because the tank is the only part that can’t be cleaned easily. It takes a pressure wash to clean it. It would probably be a good idea to add a second one there however.
KWentling
Veteran Member
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Wow. Sorry I tried to help. I stand by everything I posted and if you do a little research I think you'll find it's accurate. Not going to argue with you.
LD1
Epic Contributor
So is it fixed and working now? So I dont have to try to decipher exactly what is going on and whether the filter is on the suction line or return line.....because you contradict yourself several times about that.
oldnslo
Super Member
CMR
If possible Make sure the inlet line to the pump is full of oil before trying to operate the pump.
Also like LeeJohn stated make sure the filter element is correct. Several people have reported problems with after market filter elements in the suction line of pumps.
Kwentling is correct filter in the pump inlet is not best idea but a lot of systems are made that way.
If possible Make sure the inlet line to the pump is full of oil before trying to operate the pump.
Also like LeeJohn stated make sure the filter element is correct. Several people have reported problems with after market filter elements in the suction line of pumps.
Kwentling is correct filter in the pump inlet is not best idea but a lot of systems are made that way.
The return line IS the suction line. I said KW was correct on that fact. What contradiction? From the tank you’ve got gravity feed only with the pump off., When the pump is on you’ve got both gravity and suction. No contradiction.
Thanks oldnslo, I always make sure there’s oil in the tank when I run the pump. Sometimes I even remember to open the ball valve. But the pump can run a few minutes with just the oil that’s in it. It’s only going about 500 rpm.
The filter is letting enough fluid through to run the 25 gpm valve and the bucket; it’s from Napa. It’s a spin on hydraulic fluid filter. If it goes bad I’ll probably just have to replace the oil, flush the lines. I doubt any damage to the pump or valve would result. If anybody has experienced such a problem I dare say it’s likely because they didn’t get the correct type filter.
LD1
Epic Contributor
Return and suction are two different things. Hence the contradiction
Hypothetical IF......If the ONE line worked as both suction AND return....what would be the point of a filter. Suction flows one way, return the other. Anything filtered out sucking would be blown back out returning.
I "assume" your system has a a line going from tank to PTO pump. THAT is the suction line.
Then a line going from the pump to the loader control valve. THAT is the pressure line.
Then a line going from the loader valve back to the tank THAT is the return line.....AND where most systems filter at.
You also said if the suction filter starves the pump then it wont hurt a thing.....you are mistaken. You run a hydraulic pump dry it wont last long at all.
My question still the same....is it working and did you get it figured out?
Yes it is working great. As I said, I cracked the pressure port on the pump which is the outlet port. Which purged the air from the pump which let fluid into the pump which primed the pump.
Your assumption on what constitutes a return line are close but not quite what my setup is. The valve return on mine T’s into my suction line, it doesn’t go to the tank because there’s only one outlet port on the bottom of the tank. So since most of the returned fluid goes back to the pump, I am safe in saying that my suction and return line is the same. But I do agree that the return line from the valve is usually referred to as The return. But both the valve and the pump have returns. One is suction the other gravity and on mine they both go in the same direction.
In any case I do not understand why you say the suction line from the tank and the return line out of the bottom of the valve go in opposite directions when they T together on their way to my pump. In my setup you could say just as well, that the valve return line is getting suction from the pump just as the tank line is. My filter is after the valve returns to the suction line so it IS filtering the valve return fluid AND the tank fluid BOTH. Because they do NOT go in opposite directions. It works great. When I started this thread I thought I asked if the pump sucked but found out from trial and error that it did.
It doesn’t take much oil to keep those pumps going but sure, if you run them dry they go bad, but they sure don’t need constant flow.
LD1
Epic Contributor
You are not doing a very good job describing the system.....which is adding to the confusion. Maybe it would warrant a picture.
In your case.....the piping UP TO the tee where the return comes in would simply be considered an extension of the tank. From that TEE to the pump is the suction line. From the TEE back to the valve would be the return.
Simple question, is the filter between the tank and the TEE (if yes it is wrong and you cam move fluid BOTH ways across the filter).
OR, is the filter between the pump and TEE. (that would be on the suction line....and not ideal but not bad).
Ideally, the filter would be on the return line....between the valve and the tank(tee).
Suction and return are NOT the same.
In your case.....the piping UP TO the tee where the return comes in would simply be considered an extension of the tank. From that TEE to the pump is the suction line. From the TEE back to the valve would be the return.
Simple question, is the filter between the tank and the TEE (if yes it is wrong and you cam move fluid BOTH ways across the filter).
OR, is the filter between the pump and TEE. (that would be on the suction line....and not ideal but not bad).
Ideally, the filter would be on the return line....between the valve and the tank(tee).
Suction and return are NOT the same.
oldnslo
Super Member
CMR
What you are attempting to describe sounds like it could be a semi closed loop system where oil returning from the valve tank port is directed into the pump inlet. While extending you are using oil from rod end and drawing oil out of the reservoir to feed the pump. When retracting the cylinder you are using oil from cap end of cylinder to feed pump and excess oil is returned to the reservoir.
Is this the system that you have?
What you are attempting to describe sounds like it could be a semi closed loop system where oil returning from the valve tank port is directed into the pump inlet. While extending you are using oil from rod end and drawing oil out of the reservoir to feed the pump. When retracting the cylinder you are using oil from cap end of cylinder to feed pump and excess oil is returned to the reservoir.
Is this the system that you have?
I don’t know what you mean by valve tank. The four cylinders have four pipes going to the valve body, and there’s a constant flow from the upper inlet of the valve body to the bottom of the valve body where it leaves to go to the T in the suction hose. The suction hose pulls from both the valve body and the reservoir (tank)
LD1
Epic Contributor
Where is the filter at? Between the tank and the TEE? Or between the TEE and the pump?
I said: “ my filter is after ( meaning downstream) the valve returns to the suction line so it is filtering the valve return fluid AND the tank fluid”.
I totally agree that suction and return are two different things. And as I said, I agree that the fluid out of the valve is return fluid. But in my setup, with the valve return fluid combining with the suction line at the T, there’s a suction line that’s got return fluid from the valve in it, which RETURNS to the pump. I think it’s purely logical to say that from the T to the pump the line is both suction line and return line. No contradiction, just a combining if two different lines
