IH backhoe - odd hydraulic problem?

I just spent a month in northern Michigan, working on a foreclosed house I bought. First chance I got to use my 1960s, IH loader-backhoe. It has some, what I regard as "strange" hydraulic problems. I'm posted this on the IH and crawler-backhoe forum also, in hope of finding someone that might have come across this problem.

It is a 3414 wheel-tractor with a loader and hoe. Tractor is basically the industrial version of the red-colored IH B-275 or B-414 tractor.

Now, I'll explain the problem. I understand how hydraulics in general work - but at the moment this thing has me a bit baffled. I do NOT fully understand this machine.

It has bascially, two hydraulic systems, and both work from one common sump/tank.

System #1 has an engine-driven hydraulic pump that powers the power-steering - or - the swing on the backhoe. It is either-or and you must choose one or the other via a diverter valve with a push-pull knob. Pump is rated a 7 GPM.

System #2 has a fairly large 17-20 GPM Cessna gear-pump driven off the front of the engine. Pretty much the same as used by Ford, Case, and some Deere machines. This pump supplies power for the front loader and all backhoe functions except the backhoe-swing. Front hydraulic pump oil runs through the front loader valve, in-series to the backhoe control valve, and then back to common-sump.

Now, here's the problem. All works fine when cold and first started. After a half-hours use, all backhoe functions get slow and weak. That includes the swing and all other hoe functions even though they are two separate systems. After awhile, the hoe is barely useable, yet the front loader works great.

To make things even a bit stranger - I discovered something by accident. The hoe boom-raise gets so weak, it can barely raise when any dirt is in the bucket. I found that . . . when it won't raise - all I have to do is put pressure on a swing-lever at the same time as hitting "boom raise" and then, the boom comes right up. Acts as if it's getting an extra boost of oil when I hit the swing lever. This has got me a bit stumped.

I checked the most obvious, but did not have a lot of time or tools while there. Oil sump is full, and there is no filter clogging. In fact, no filter at all since it's missing.

Two main questions in my head right now.

#1 is - how can hitting the swing lever make the boom raise better since they are working to separate hydraulic systems?

#2 is - how come the front loader keeps on working fine while the hoe pretty much goes dead after awhile? Both are on the same system, basically. Front loader valve is run in series through the back backhoe valve.

Try this , there are a lot of experienced heavy equipment techs on this site. Hope this helps! Gary
Heavy Equipment Forum TLB

Interesting problem and I have no direct experience to bring to bear, but couldn't resist a comment.
Even though it has two separate systems, the situation you describe shows that they are not truely independant. The weak response after the system gets good and hot suggests that a valve is sticking open or leaking somewhere in the system. Since it returns to full power when the swing system is being activated, it must be impacting the other system by either applying a back pressure to reduce pressure or increasing pressue in some manner that makes the faulty valve work. I'd look for a place to insert two pressure gauges into the two circuits and watch the behavior as it warms up. I'd pay particular attention to the pressure relief valves, and see if there is one that could be leaking, but could be affected by back pressure from the other circuit. Perhaps both circuits share a common return to the sump from the relief valves. A detailed hydraulic schematic would sure help.
good luck and report back what you find.

Oh goody. Another forum to start checking everyday. Thanks.

Sounds to me like your diverter valve is bad, causing leakage back to the other supposedly independent system. You're losing pressure to somewhere, I'd look there first.

does the diverter valve look like it is original equipment or a later add on.usually all hoe systems are fed off the front pump.I believe the valve setup for the hoe is worn out and leaking thru to return to sump.when you hit the swing and boom at the same time it closes return and supplies all oil to function

How old is this beast?

All I can tell you is that it sounds for all the world like a load sensing system.
Ford used this system with tandem gear pumps and closed center load sensing valves in conjunction with an unloading valve from the early 80's onwards.

If you want to understand the basic function of it, it works like a standard PFC hydraulic system except that the pilot flow actuates teh unload valve instead of the stroke control on a variable piston pump.

Does it have a third, small load sense line coming from the valve banks? That would be the calling card for that system.

I'm not familiar with those old hoes, but given that IH was quite early to the PFC game (I think with the 86 series), it's not impossible that they did some experimentation on the backhoes similar to what Ford did...
It was a matter of giving most of the benefits of CC control to the durability and simplicity of an OC gear pump system.


If that's what you're dealing with it sounds as though there is a problem with one of the shuttles in the valve bank or line that is not seating properly. When you cause demand on the loader, that opens the sensing valve which would then supply oil to the hoe... that's my guess as to why it works like that.
However, if it's a purely open or tandem center system, you've got me stumped.

Rod

We had a 2414 forklift, with the same quirky problem, we were able to run a brake cylinder hone through the bore of the diverter valve, it had some burrs that made the valve stick or hang up in one position. On that one, the factory had some kind of fix for the valve piston, it involved drilling a small hole diagonally through the piston, but this was to give priority to the power steering circuit, over the lift function.

Hi JD,

Classic sign of the oil getting too hot. Add a oil cooler on the front of the engine radiator.

I've also used 10w30 for the oil that helps in the AZ heat. About 300hrs on the oil w/o problems.

T_Bone

Hi JD,

Classic sign of the oil getting too hot. Add a oil cooler on the front of the engine radiator.

I've also used 10w30 for the oil that helps in the AZ heat. About 300hrs on the oil w/o problems.

T_Bone

That all makes sense. I have a hydraulic schematic from my IH manual. Since the hoe works better when I hit the swing lever, I was looking for any connection between the two systems. #1 is the connection at the oil reservoir. They both draw oil from it. The only other connection between the two systems is not explained, but it shows in the diagram. Keep in mind that there are two systems with their own pumps. System #1 is power steering and backhoe swing. System #2 is front loader and all backhoe functions except swing. Only anomolie I see is an extra line between the swing valve pack and the hoe valve pack. This connection is not explained in the IH book. I suspect it has something to do with all this. Eack valve pack has it's own "in" coming from the oil reservoir, and it's own "out" going back to the reservoir. But . . . the swing pack has an extra line that connects to the backhoe valve pack, for reasons unknown to me.

<a href="http://s104.photobucket.com/albums/m162/jdemaris/?action=view&current=3414hydraulics.jpg" target="_blank"> </a>

The diverter-valve is OEM. It really can't go bad enough for things to not work. All it can to is wear out and leak. It's just push-pull diverter valve, NOT an automatic priority valve.
My 4000 Ford backhoe has the same type valve to separate the front loader and back hoe.

For some strange reason, IH used the power steering system to power the swing circuit in the backhoe. Maybe so swing would be slow? I've never seen this type of setup in any other make machine. You can have power steering, or swing in the backhoe, but cannot have both at one time.

The diagram, if it is to be trusted, seems to imply that the swing releif is regenerated into the boom supply pack. That still doesn't explain why the boom performs better unless you're dead heading the swing?
It really makes me wonder if the diagram truly represents the system you have in place on the tractor?


Rod

Oil getting hot and foaming?

According to your diagram, the 9 gpm pump (or 7) goes into the top of the flow divider, out the bottom, and then over the all the hoe systems. Starting with the swing and stabilizer.

How do the stabilizers work after it gets hot? Can you move the bucket and boom with the small pump maybe slower than normal just after you start it? Are you sure the pilot valve doesn't have a pop off valve and lines going to an oil cooler and then back to the resevoir to maintain an open system circuit when no valves are being operated?

The drawing appears to be from a system that has the dual pumps in the pump housing such as on a 606-656-2606.

Think I'd try would be to unhook the line between the two valve spool banks and bull plug both sides. Then you can isolate each system to try them out. Both spool valve banks still have a pressure relief valve for a return to the resevoir. That may be a good place to put a pressure guage if you have one.

I'd pull all the pop off valves and see if there is any gunk under any of them.

After reading what others are saying, I'm leaning towards the swing valve spool bank or a bad oring or piston seal leak in the swing mechanism. You could isolate that further depending upon if it acts the same when you move the swing as when you move the stabilizers. Do the swing mechanism/cylinder(s) leak and does it make a difference where the swing is such as all the way to one end or the other end or in the middle?

Not a dual-pump in one housing. It has two totally separate hydraulic pumps. One is a Cessna gear pump driven off the front crankshaft pulley. The other is mounted directly on the engine and gear-driven. Basically, what IH did was tap into the tractor power-steering circuit to power the swing in the hoe - but nothing else in the hoe.

In regard to seals leaking in the valve spools - there aren't any. The spools in this thing seal like most do - by metal to metal contact. Rubber seals in the valve banks only stop leaks but don't hold any pressure. Certainly valve spools and bores can get scored and worn over item - but when that happens you get lots of leaking oil -not system malfunctions.

After the hoe gets hot, nothing in the hoe works properly. All functions get slow and weak. That includes little to no swing power even though that is on its own separate system. At first, since the machine is missing its hydraulic filter and has been run that way for a long time - I figured maybe both hydraulic pumps are simply worn out. But . . . if that was true, the front loader also should work lousy once hot - yet it works fine. Also, why does the hoe boom raise great when I jam on the swing lever? That one really has me baffled. It acts like it sends a rush of extra oil to the boom. (might do the same in other hoe functions, but I didn't experiment too much). This is why I'm calling this a "oddball" problem. And, to make it worse, I don't have it here in my shop. It's parked 750 miles away in northern Michigan, and I won't be back up until late summer. I'm trying to figure out what parts I should bring on the next trip. On this trip, I was in a hurry to get a new septic system in, so I nursed the hoe through the job. If I hadn't discovered the trick of jamming on the swing lever to raise the boom, I could not have finished. Once the hoe was hot, it could not raise the boom out of the hole with a full bucket of dirt (until I hit the swing, which I discovered by accident).

Looking at the diagram, the loader valve and the swing/stab valve are power beyond. If all the loader spools are in neutral, oil from the 17 GPM flows to the Bm Crd Bkt valve from the loader valve's power beyond port. The 9 GPM flows to the swing/stab valve and if the spools are in neutral, the flow goes back and tees into the inlet pipe to the Bm Crd Bkt valve. (from upper left of sw valve to tee on rt side of BmCrdBkt valve)

What I suspect your problem is:
When you load the boom or other function Crd Bkt, the 17 GPM is flowing backward thru the tee and exiting to tank thru the swing/stab valve some where. Since there isn't a detailed schematic of the swing/stab valve I will speculate. The unit works good when cold so suspect a valve section casting is cracked or has a pin hole. A quick test would be to leave the divertor poking oil at the power steering circuit. Remove the pipe from the tee and cap both ends. If the boom now works fine, the oil is backflushing thru the swing/stab valve. I think there should be an isolating check valve in the sw valve to prevent the Bm flow from poking backwards into the 9GPM curcuit.

Your problem should be in the swing/stab valve for when you operate swing, you are blocking the backflush from the 17GPM from getting to tank.

Hope this explanation helps but I have made a few assumptions so it may not be 100%.

BTW, most valves that have three ports, pump in, tank out, and the third goes to the next valve down stream is a power beyond set up.

Seems you are thinking more clearly than I am at the moment. Your hypothesis makes sense and I'll have to study it further. Thanks to you and all others for the input.

I agree this may be it. The reverse flow could do it easily. I think I would put a positive check valve in the line from the swing stab block. Where the T is located, there is a directional arrow. A check there flowing in the direction of the arrow would prevent the back flow while providing a path. Fixing the seals and centering (possible issue) in that block seems to me to be needed. JimN

I bet you won't get to take too many hydraulic fittings with you since there is probably a mix of O ring boss, JIC, and pipe thread and then a mix of 8, 10, 12, and 16 or bigger for sizes. Maybe you can get some pics and measurements. Good luck.