Quick IH756 Hydraulic help

nw_bearcat · Jun 20, 2012

IH756 D. Don't have shop manual, and trying to keep haying going, so trying to not hold things up to wait on one just right now...

Seems to steer fine. Lifts 15' batwing fine. Lifts 1500+ hay bales fine. Bought new to us moco this year for haying. Seems to lift the header REALLY slow at end of field. Local guy says pump weak, more I think about it more seems odd that lifts 3pt ok, but remotes slow. MOCO is a 12' sickle hydraswing that uses a couple of fairly long travel 2.5" or so cylinders to lift, so don't know if those require more pressure than the stuff we use already. Anyway...if it comes to that...it sounds like the main pump is behind a cover on the LH side opposite the hydraulic filter. Is R&R as simple as dump oil, pulling that cover off, and pump comes with it? What holds/connects pump to the other goodies inside rear end?

thanks for help

pete 23 · Jun 20, 2012

I would flow rate the pump. If that is not a possibility, you might just slip in a higher pressure relief valve from a newer tractor. You could go from 1600 psi to 2200 psi. With a small cyl diameter that may be your problem. Relief valve is located in seat support, right side, has 1 1/8 in hex head, about 3 inches long with screen in inside end.

IaGary · Jun 20, 2012

I would try a larger diameter cylinder first.

I had a 3 inch on my 9 foot mower conditioner.

A 3 inch will lift 30% more than a 2.5.

If a 2.5 lifts 1500 pounds the 3 inch will lift 2000 with the same input pressure.

Gary

nw_bearcat · Jun 20, 2012

follow up question...is there anything else required to replace the pump other than the pump itself? Gaskets, orings etc?

Should have also added, doesn't seem to be any chatter or whine like a pressure relief valve would usually make...

nw_bearcat · Jun 20, 2012

cylinders are kinda made into the frame, not sure there's room to upsize, and currently they're not a typical cylinder, some kind of application specific type deal

Owen Aaland · Jun 20, 2012

The relief valve is a pilot operated valve and usually will not make much noise when bypassing the oil. If you need more pressure than the relief valve is set for replacing the pump will not help you at all. You could spend a lot of money with no improvement if you don't determine what the problem is before throwing parts at it.

nw_bearcat · Jun 20, 2012

Would that relief valve be making a noise if not good?

If I replace will this just be a band-aid and I'll still need to do the pump soon?

Looks like pump would cost just over $400 + the time to do it, depending on what else needed to change, relief valve looks like a quick fix and a $200 part. hmmm

mkirsch · Jun 21, 2012

Modern mower-conditioners (made in the last 15-20 years) are generally very HEAVY, and were designed for late-model tractors with 2500-3000 PSI hydraulic systems. Small cylinders for quick cycle times.

The old 1960's technology tractors were never designed to lift something like this.

I would pressure test and flow test the hydraulics before spending any money on anything.

caterpillar guy · Jun 21, 2012

If you get a pressure gage and screw it in the end of the coupler, and plug it in then pull your lever you will get your pressure reading on both. The relief valve and what the pump can do. If you only get like 1200PSI the pump is suspect if you get upwards of 1600to 2200 your pump is probably good and your tripping the relief So you will know it is ok.This will leave flow as the last issue this can be checked if need be by using a flow meter or you can run into a pail as some body pours more oil in to the trans.

Anonymous-0 · Jun 21, 2012

You might try different tips and/or couplers, they wont flow the oil, this was always a problem on heavy loads or too small cylinders. They must be compatable with each other, many different types out there, test with just pushing tips against each other, if one ball is stronger that could be problem. Also you can increase system relief hi pressure by swapping cartridge in side of seat with a another, they are made 1750/2000/2250/2500psi, would try 2250 first. IH/CNH part 396729R91.

nw_bearcat · Jun 21, 2012

Thanks guys. Looking into a pressure gauge to check things before tossing $ at it.

Help me think through some more...dealer pushing us to replace pump. Even with new pump, I'll likely need to replace relief calve too right? New pump=good pressure, but relief still set to low pressure, so I couldn't take advantage of new pump capacity right? May as well put in relief and see if that fixes, and do pump if not right?

Also, I see a 12gpm and 17gpm pump...don't run any motors with it, but any downside to putting in 17gpm pump? Anything else I'd have to change?

Thanks

craigreavley · Jun 21, 2012

Our 966 Lifts our hesston 1085 slowly.It is a 9 foot moco. We just bought a 9 foot heston 1120 and it lifts it very quickly at an idle. The only difference in the 2 machines is the diameter of the hydraulic hose the newer moco has the small lines. I wonder if it is a flow issue more so than a pressure issue. the smaller the lines the faster the fluid gets there??? I dont know but the new one lifts twice as fast with the same cylinder size just small lines????

Anonymous-0 · Jun 21, 2012

The pumps std usually 12 GPM, opt was 15 GPM & 17, as a rule of thumb takes 1 HP per GPM, the systems on 06/26/56/66/86 close to same. If you have another IH tractor around they all have a cartridge you could swap just as a test. Any of the above has the cartridge in the same location with the exception of 86 series, they are under cab corner on rh as I recall.

mazemeister · Jun 21, 2012

check out the picture on case ih website. there's a $15 gasket and 4 o rings you might as well replace while you're in there. the pump is bolted to that cover with a spacer in between. so you leave the 4 bolts in the middle, pull the whole thing out, then change out the pump.

from your original post it sounds like it will lift header all the way, just not fast enough. if you start with the header all the way down, does it start to lift faster, then slow down when it takes the weight off the ground? that might indicate a slightly worn pump, as leakage increases (and pump output decreases) with increased pressure. if not, it sounds like you've got a restriction somewhere.

nw_bearcat · Jun 23, 2012

Update with a pressure gauge plumbed into the pressure side of the lift circuit.

Running this morning with the gauge inline. Cool oil(77*) 1000rpm or 2000 rpm about 1300-1400psi while lifting and 1500psi at the end of the stroke.
After cutting 3-4 acres (oil hot) 1300-1400 lifting and 1500 end of stroke regardless of engine rpm. At no time did I see it top 1500psi.

I think we're going to start with a 886 relief valve and see if that lets us boost the pressure up some.

Quick IH756 Hydraulic help

Our Phone System is Down!

Please use the Contact us Form

We are working to resolve the issue ASAP! Thanks for your patience!

nw_bearcat

Member

pete 23

Well-known Member

IaGary

Well-known Member

nw_bearcat

Member

nw_bearcat

Member

Owen Aaland

Well-known Member

nw_bearcat

Member

mkirsch

Well-known Member

caterpillar guy

Well-known Member

Anonymous-0

Well-known Member

nw_bearcat

Member

craigreavley

Member

Anonymous-0

Well-known Member

mazemeister

Member

nw_bearcat

Member

Similar threads