IH856 biggest ever in my shop hyd problems

old

Well-known Member
So one of the guys from Y-T just hauled in his 856 for me to work on. It looses steering and brakes but if you work the hyd control for the outlets hyds come back. So any educated guesses as to what might be going bad. Filters have been changed and pump also. He has been told problem something in the rear end area leaking so loosing hyd pressure.

So what do you guys think??
Thanks

Also if this thing was 2 inches taller it would not have fit in the shop
 
Is it 5 gallons over full? If not do that first. There are suction side Oring problems, and a suction tube in the upper reaches of the finals area that can cause issues. Jim
 
I haven't checked any thing on it as of yet. I ask questions first then grab the wrenches. The guy who brought it to me to work on said he was told to pull he plate that the center link hooks to to have a look see in side does that sound right.
Also the brakes are iffy and there also hyd
 
The center link "hole" can provide visibility to the tube, but not the Oring. The Oring (IIRC) requires a split to fix, but over filling solves it. Jim
 
Okay so where is the split?? Is it at the rear of the transmission to the rear end or some place else. Makes me wonder if my shop set up will handle the weight. and is it worth what the 20 plus hours to do the job
 
Well First off the rear Hyd.'s have nothing to do with Steering , brakes or lube , that is all on the MCV pump that is located behind the MCV valve on the left side center section . That pump is a 9 GPM pump . Loss of steering and brakes is on the MCV side . This can be caused by low oil level , plugged hyd filter , sucking of air at or around the filter cover . Iffy brakes , well the problem here more then likely is oil soaked disc's , brake drums full of dust and oil , cocked brake piston , frozen or broke return springs , stuck or frozen brake self adjusters and low hyd pressure . Now as to splitting it unless you have splitting stand that will support a 6 to 7 ton tractor and you have the book to read up on before you take the wrench to it ya don't want to go there . Ya always hear about the pesty o/ring , Well if it can suck air between the range and speed transmission thru the gasket good luck . Those that claim this have never Split one . You can remove every bolt and the two halfs are stuck tight , to the point that 99% of the time i have to drive two to four stiff bladed scrapers between the two half with a 4 pound hammer to get the gasket to let go . Then once ya get it to break loose you have to get the PTO driven gearto come off the shaft up ft in the bottom of the speed transmission and have it fall out the bottom and separate the two half about three feet . So If i was working on this i would start with a filter change and make sure the square o/ring was still inplace on the tin filter cover behind the hyd filter , next i would make sure the filter cover was Flat around the bolt holes and install a new gskt . When tightening down the filter cover ya don't need a six foot cheater pipe to tighten up the bolts 20 ft pounds is enough . Next i would make sure that the tel tale light in the gauge cluster was working That is the one that says OIL , it does double duty as it is also the engine oil pressure light . This light shouold come on each time you depress the clutch pedal as the linkage on the clutch also goes to the T/A dump valve to dump pressure off the T/A clutch pac.'s so you can get it out of gear. Next up on th list is running a flow rate on the MCV and a pressure check . This requires special stuff , Ya need the one test valve you have to install in the MCV and a way to run the flow test when the oil is up to operating temp . some have said to add five gallon extra after you have the fluid level up to the full mark this will help if you have and air sucking problem on the pick up tube as sometimes they do crack where the bracket is welded to the tube and adding five will put the tube under the oil level . To get to the tube ya have to remove the rock shaft housing and it is HEAVY , it also has linkage hanging down off the right rear corner that when going back on has to align with the linkage coming up from the bottom .
 
The MVC pump has been replace wit ha new one so that is not likely where the problem is but could be something like low oil which I'll look in the manual and check where that is and where to fill etc.
 
(quoted from post at 08:14:47 09/01/20) The MVC pump has been replace wit ha new one so that is not likely where the problem is but could be something like low oil which I'll look in the manual and check where that is and where to fill etc.

Don't be so quick to dismiss this as a possibility. The pump could be bad out of the box, installation could have been screwed up. In fact if I'm not mistaken there are some o-rings that are real easy to screw up in the MCV installation.

BTW working the hydraulics have NOTHING to do with the power steering and brakes coming back. The same would happen if you sat there doing nothing. All working the hydraulics does is give you something to do.
 
Is there a way to test PSI on the MVC with out having to have a bunch of special tools. Also is the hyd for the MVC the same as for the rest of the tractor?? I have not gotten into either one of the manual as of yet to know ll of that. I do know it has disk type brakes and I'll be checking them for oil and wear etc.
 
well you have not check the tel tale light out yet have you ?? so for starters you do not know if you have pressure or not . I don't care how you cut it here unless you have the proper fittings and knowen GOOD gauges to plumb into the MCV you are NOT going to see what you have. As far as a flow test ya have to plumb into the system . A crude way is a watch and a bucket , BUT tryen to do this at rated RPM you will usually end up with a lot of oil on the ground . The special test valve i know you will not have and as to where to get one now is any bodys guess i have had mine for over 35 years . Now as for the new PUMP and someone else installing it oh here we go . LIKE one said they could have left out and O/ring , ya could have a blowen gskt between the plates of the MCV along with a blowen O/Ring , sump check plug vary easily been left out that sets down in a hole behind the MCV on the lower right hand corner and has a small spring that looks like a ball point pen spring . You could have a sticking priority valve in the MCV . You could have weak springs in the MCV . They are almost like a valve body of and automatic trans mission , lots of springs of different strength leinght and size and ya need to massure and compair to the BOOK spec.s, Pressure regulator that comes in the spring kit has to be cut for the correct pressure per app. as they are now a one size you make it fit all. Out of the Pkg i have seen some push the pressure well over 350 and the best ya need on lock up is 275 . Sorry i am not there to hold your hand . And one more little tidbit here the gskt for the MCV is also a shim for gear contact and back lash and you are to match what came off org . and if someone else has been there before you can bet your bippy they did not know this and just stuffed it back together . These are not your old M's The fill for the transmission is in the floor plate where the transmission dip stick is . DO NOT TRY AND CHECK OIL LEVEL WITH THE ENGINE RUNNING , The dip stick sets between two gears and FI you happen to get it into the gears she will get sucked out of your hand and you will get to learn all about gear replacement in the Range transmission first hand .
 
At this point I have yet to do any thing to it other then try to research what things I need to look at first. I figure the very first thing I will do is check hyd fluid level and make sure it is full. Then move on the things like seeing what the light does if it even works and if it doesn't work fix that to start with. I've looked in both the I-T manual and the operator's manual and both leave a lot to be figured out as far as location if things due to poor pictures and descriptions
 
Just ask . I can darn near even tell ya what tools ya need for the job at hand . I can NOT tell you how many of those tractors i have worked on . And the addition of all the special tools i got when i bought 90% of a closing I H dealers shop made my life a lot easier and gave me a leg up on tractor repair . The Flow rater and all the fittings and all the Good test gauges save me time and customers money . I do not throw parts at a problem till i know the problem . when it comes to hyd. the flow rate gets hooked up and i can bring the oil temp up to test spec.s and do the tests . that alone to me was worth the day at the sale . The only thing i do not have is the extra piece needed for the NEW systems to use it with . So once you get past the early 86 series tractors i am done for .
 
Since you answer me back so fast I'll tell you want I just found and then make a new post for others.
#1 I checked the hyd fluid level and it is over full which I have been told is sort of needed. How much I cannot tell for sure other then maybe an inch above the full mark
#2 none of the indicator lights work and the one off the MVC appears not to even have a wire going to the probe at the MVC. I wonder if I could use my test light and hook it to the probe tab and the wire to the battery and use it as the light you talk about watching when you push the clutch down
#3 while I know it should not matter while I had it running I tried the steering and it was hard to turn and jerky. I pull the hyd remote levers and tried the steering again and it worked much better and the tires even turned a good bit where as before they did not turn much at all
 
Ok , the sender on the MCV is a GROUNDING sender and yes you can Hook to the POS post . The wire that Should be going to the sender should be a GRAY wire and same color as the one going to the engine if it is still there . The oil level as you see it tells me that it is about five over that is fine . Again here the remote valves have NOTHING to do with the Ft. half of the tractor and run off a totally different pump that is located on the lower Left rear frame behind the left step . all of your problems lie with the MCV . You will have to drain the center section of the tractor to remove the MCV and this can be done by the drain plugs under the center section . You will not have to drain the rear end . You will get around ten gallon of oil out of the center section maybe a shade more being over full. If you remove the MCV pay attention to where the bolts all go as they are NOT all the same and there are four bolts you do not need to remove as then hold the pump to the MCV and USUALLY have copper washers behind them . also like i said earlier when removing watch for the sump check plug and spring lower right hand corner .
 
Guess maybe I should had the guy leave the old MVC and the o-ring placement diagram with the tractor. I'm also thinking I should look at the brake before doing the MVC area so if parts are needed I can maybe only have to order once. Odd how working the remotes made it steer better for a little bit
 
Absolutely no connection between the two . as for the lay out of the MCv it is in the IT manual . I H manual # 32 page 17 and 18 everything ya need to know but were afraid to ask .
 
So if the 2 systems are not connected other then by using the same fluid why did the remote make the steering work for a moment. I haven't look in the I-T manual as of yet for the MVC but will soon.
 
I also forgot to ask if jacking it up so the front tires are off the ground would help tell me anything as for as the steering and I noticed both the hyd lines going up under the hood looked pretty rough any chance a line could be bad and blocking fluid flow
 
How about maybe a filter problem that when the remotes are messed with pushes the hyd fluid threw the filter for a moment a bit better
 
Not sayen you don't have a plugged filter but still no way to PUSH fluid thru as any return will just dump down into the rear end and still have to be SUCKED UP over down and around then across to the MCV pump . Open center system on both as Oil is always moving and pump always pumping .
 
Loss of brakes and steering and the MVC has been changed and maybe the filter
 
TV has it right. Only thing I can suggest is if you have a helper start the tractor. And with it running pull the plug on the back of the MVC it is facing rearwards. I believe it is the smaller one maybe 5/8 wrench or 3/4 be ready for oil in a big way there is a spring and valve in there so soon as the oil comes shut it down and with plug reinstalled start and see if the steering works if so then the pump is not priming if no oil or steer then pump is not making pressure or volume or both.
 
I will have to take a look at that tomorrow and see where your talking about. I know the sense probe is towards the back but I did not notice a plug in that area
 
I just looked at the 856. There are 3 plugs where your talking about. One if up high and behind the clutch linkage. Then below it is the idiot light sender and below the sender is a large plug as in 3/4 maybe and below it is a smaller one that is 5/8 or 9/16 so which one is the one your talking about
 
Okay so I hooked up my test light to the pressure switch. But it did not light up with it not running or with it running so does that mean the pressure switch on the MCV is bad??? I also while it was running pushed the clutch pedal down and the light did not come on. And yes I made sure the light would light by touching a good ground before hooking to the pressure switch
 

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Back
Top