Posted by jdemaris on July 22, 2009 at 07:12:09 from (67.142.130.37):
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.
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