I recently purchased this 1840 with the engine locked up (water in base pan) Machine sat more than it was used. Reading 249 hours. It was in good shape other than engine. Seller said that everything worked as it should when parked. When I got machine home i pulled cab, engine, tandem pumps, all hoses. I left motors, sprockets and chains in place. Properly capped motors and chain boxes and completely cleaned and repainted machine, rebuilt engine (4-390). everything appeared to be fine with tandem pump, so cleaned and painted and installed Got machine back together and runs great. Problem is that it will move forward and reverse, but with no power either way or either side. the warmer it gets the worse it gets until it will not move. it will not steer at all. has more power in reverse than forward, but nothing to be happy about. it will only move if close to wide open throttle. i have 300psi charge pressure. no pressure at either port on pump to motors. did the drain test and no oil coming from motor drains. i pulled all of the valves (circuit relief, bypass, charge pressure) and they appear to be fine, but cant be sure. i would like to mention that one of the post i read said that it should be hard to turn the input shaft. i recall (when tandem pump was out) that it was easy to turn input shaft. my next step is to remove tandem pump and go through it, but seems like it could be a simple fix and would hate to go through all of that if not necessary. i also replaced 90% of the hoses and cleaned them well before installing.
Welcome to HEF @Justice1840 Sounds heartbreaking...... The charge pressure at 300psi is a little low, - is that reading at full RPM? Is that reading when cold? Does it change at operating temp? You also need to test the charge pressure again & see how much it drops when the drive is engaged under load - ie against the brakes (if they are working) slowly load the drive until the engine RPM begins to fall - the charge pressure should only drop about 20psi - any more & you need to do an autopsy on the hydrostatics.
-yes it is heartbreaking. so close, i thought.... -yes 300 plus or minus at full throttle -i will run again tomorrow to be sure what it does hot vs cold, not sure -i did test it under load with brakes engaged, it dropped, but again will check tomorrow to be sure how much -engine never drops at all. i can have both left and right side wide open against brake and no engine rpm drop Thanks for your reply
So I checked charge pressure again this morning and got a different reading than before. I will explain the best I can. At initial start up with low RPM, I am getting 150psi constant. As I open the throttle pressure will go up. Lets say half throttle about 200psi. If I stay there for a minute it will start to fall, maybe 175psi. Than full throttle I'm around 250psi. Brakes engaged, moved drive control forward (right side) I loose about 5-10psi. The same in reverse. On the left side when I move control forward I get the same thing. When I move the left side in reverse, the gauge jumps up to around 300PSI and motor wines like low on oil. Now both controls in neutral wide open throttle the gauge is jumping rapidly from 5psi - 275psi. I throttle down to idle and have 5-10psi.
My service manual says that I should have a minimum 300psi charge pressure. I understand that I am lower than 300psi. I am confused on why pressure is acting strange when left side reverse is engaged. Could a valve be stuck open and robbing pressure? Even though I am low on charge pressure shouldn't I still be getting some pressure to motors? When I put 5000psi gauge to A and B motor ports the gauge is hardly moving off of zero. If I cap off the hoses going to motors I get no rpm drop from engine. Nothing changes
It does seem to be very peculiar.... Can you explain why the engine was "locked up", ie -"water in base pan". Was water in the hydraulic tank as well?? It seems there is a problem with the servo pistons binding & not allowing high pressure oil from the main pumps??
There farm was flooded and supposedly water came up just over oil pan. When oil pan was removed you could actually see the water line. My guess was oil pan was leaking. It had one main bearing stuck. There was no water in hydraulic system. Oil was clean. The servos being stuck sounds believable. I had that thought also. Can I check servos without removing the pumps? It seems from what I can tell that the swash plate holds servo in? I’m not sure. I’m new to this I added a shim to the charge pressure check valve, just to see if pressure would rise. Little to no change I also checked case drain pressure today from pump, 10psi
Are u getting proper suction for charge pump?
I’m not sure about getting proper suction for charge pump. Can you explain how to check this?
That is a strange issue. You've probably already checked all the simple stuff but just the same make sure the reservoir is full of the proper fluid (10w30 motor oil I believe) and the filter is good. I agree it sounds like the servos aren't stroking for some reason. You can check the pressure on the servo pistons by attaching gauges to the large ports on each servo end plate. In neutral the pressure difference should be zero and it should increase from there depending on load and how far the control is stroked. I believe you can also remove the end plates to visually inspect the servo housings. This may be of some help if you haven't seen it already. http://files.danfoss.com/documents/11026743.pdf
Short of visually inspecting for any obstruction that may have been left in place during assembly - ie plastic cap, rag - I'm not sure either...
Ok. I will try to put a gauge on servo caps and see what happens
So I checked pressures on left pump servo. I’m not 100percent sure what the pressure is supposed to be, but I’m sure it’s not supposed to be what I’m getting. Reverse side of left servo I am getting around zero pressure in neutral. Gradually goes up as I move lever. Wide open I’m getting around 300psi Left servo forward side I’m getting around 250psi in neutral. I’m getting no change when lever is moved forward. If I move lever in reverse pressure goes to nearly zero ??????
There is something very strange there.... Technically, the LHS machine should be trying to drive forward while in neutral & it's not? Can you really believe the previous owners statement that "everything worked fine when we parked it up"....... Was there any evidence the pumps have/have not been tampered with before you pulled it apart? I would be pulling the pumps & taking them to someone who really knows how they are supposed to work.
Yea I agree, the machine should be moving in “neutral” and it’s not. However it does move forward when I move lever forward. Very strange. I’m wondering if one of the o-rings on servo is torn and allowing pressure? Not sure if it would do this or not. I know the people that I bought it from and don’t believe that they would have lied to me, but can’t be sure on that either. I didn’t see any evidence that it had been worked on before. I decided to remove the pumps today. Just got them out. Will attempt to pull apart tomorrow and hopefully see the obvious. My biggest fear is putting it back in and it doing the same thing. Was hoping to find the issue before pulling it out Thanks for all of the reply’s. I will keep you posted on what I find
Got the pumps disassembled today. Very clean inside, no metal shavings or debris that I could see. The servos appear to be ok as far as o-rings go and no scoring. They turn, but cannot move them side to side. Is this normal? I have quite a bit of scoring on both valve plates and also on cylinder block and piston faces. I will try to post pictures. Other than that I don’t see any obvious issues. Would these things cause my issue? How much can I take off of valve plates, cylinder blocks, and pistons without replacing? Or should I just replace?
Well, that sheds some light on the issue! I don't consider myself an expert on these as I sublet these rebuilds to Sunstrand specialists for warranty reasons. However I have seen inside many of them. Yes, I believe this is your problem. I would think the servo pistons (without swash plates attached) should slide without too much force required to move them. The shop I use, has a lapping machine to polish those mating surfaces. Your end plates look like throw aways. The slippers look like they may clean up. How does the charge pump look? I hate to break it to you, but the drive motors will look the same.........
so the servo as pictured should move to and from end cap?
If it doesn't move, it can't vary the swash plate. There is an internal spring inside the piston, which centralises the piston in the housing to give the neutral position. I'm not sure how much tension it has on it, but it has to move.
I figured, just want to make sure before I try to pull apart. Not sure how both are stuck like that. Just my luck. Ok so I will try to free up servos, get new end plates, replace all seals, polish swash plates and slippers. Any other suggestions?
A new charge pump for sure. And pull the drive motors & strip, inspect, clean & repair them. Plus, thoroughly clean those high pressure loop hoses. If you don't, any contamination/worn items in them will continue to wear after you refit your rebuilt pumps & undo all the time & money spent - within a few hours of operation.
Understood. Will attempt the motors after getting this thing back together. What did you see wrong with the charge pump?
Scoring on the alloy end plate & the gerotor. It's all percentages & that scoring causes leakage. The charge pressure was low wasn't it?
True true. Glad you mentioned it, that would have went back in. Thanks for all of your input. Again, this is my first time so if you see anything else please let me know. Going to try to order parts tomorrow. I will keep you posted.
Get the Sunstrand numbers off the pump & call a Sauer Danfoss agent to compare prices with CNH. Consider service exchange prices on the M91 pumps if you can find them also. Those drive motors are made for Case so there isn't an after market option on parts for them. The output shaft is Case OE. You may find seal kits over there, but I've always had to use CNH genuine seal kits for them here in Australia.
Great thanks
That is issue....cavitation for sure...sorry about your luck....they can be rebuilt. If case is good....you can talk to jack at evco in tuttle ok...he is very good at rebuilding...also very fair....i can get pilot controlled rexroth tandem hydros at a very good price...i have an OEM deal with them. these are the drills we build from scratch...it has a tandem rexroth A22vg series
Waiting on parts for tandem pump so I decided to pull motors. I pulled one apart so far and it looks like new inside. No scoring at all. All that I can figure is I must have contaminated the pump with something when I had it out for cleaning and painting. Can’t be sure. Your thoughts??? Being a closed loop system you would think that whatever went through pumps also went through motors. I was never getting pressure to motors even at initial start up as far as I know, so maybe it stayed contained in pumps??? I don’t know just guessing.This leads me to believe I could have another issue, but again I’m guessing. I did think of something that I meant to mention at the beginning. With all 4 tires off the ground, I can turn the tires on either side with almost no restriction. Very little restriction, none, very little, none, and so on. I feel like it should have a lot of restriction and be hard to turn???
The wheels should not turn freely when in the air. Is it at all possible the bypasses were not fully seated? Nevermind, I see you did check the bypass valve.
It is all very unusual.... The wheels should be very hard to turn - if at all. ......The towing valves weren't open were they????
Looks to me like like not enough charge pressure...oil starvation...did you start the machine without filling the case first from the case drain
Bypassed/tow valves were removed and inspected. Looked good from what I could tell. Replaced them to book tourque specs. So I believe they were seated, but can’t be sure I definitely had oil in the system. I did not do anything with case drain when I installed though. Can you explain? If tandem pumps were low on oil or no oil, would it do this damage? I’m just curious if it is running low on oil somehow. Every time that I have pulled a plug, gauge, or hose there has been oil there. One thing that I had posted earlier though is that after running for a couple of minutes charge pressure is dropping to 5-10psi. Does that mean I’m not getting enough oil supply?
If you dont fill the case the pump runs dry till it does. If the wheels turn with the counter balance valves released and the motors are good then there was not enough oil in the loop. Anyways i have been a hydraulic tech and an authorized hydraulic system designer for danfoss and rexroth for years...closed looped systems are a lot more complicated then u think...the fact that you, what i assume is ordered the barrels and pistons and maybe the slippers , and did not know that ALL piston pumps must start with pre filled cases tells me that you are out of your element...send it out to someone...there is very special tools to set these things....especially a tandem pump...
I appreciate your concern. But the fact is that it did have oil in it. My thought is the oil is going somewhere and not returning fast enough. Like i said I have insufficient charge pressure, but still 200-300psi through the start up process. After running for a few minutes I only have 5-10psi. Sounds to me that there was not enough oil there. Why? I’m no hydraulic tech or designer by any stretch of the imagination, but I think very logically and this makes no since to me unless something is restricting the oil from returning or something similar. Maybe a valve open that shouldn’t be. I don’t know that’s why I’m asking. Sending it out is not an option. If I can’t fix it than I don’t need to own it. So can we get past the sending out or buying new. It’s a challenge now and I’m going to fix it if I have to rebuild it 10 times. I will most likely never be a hydraulic tech or a designer or whatever you would like to call yourself, but by the time this is done, by myself, and with the help of the very knowledgeable people on here, that have already been a great help, I will be able to trouble shoot my machine and have ample knowledge about it if another problem ever shows itself. I did not order a new barrel or pistons. I am having those parts lapped. I’m waiting on seal kit and charge pump
Good luck.....and learn....that pump was not contaminated it was cavitated. The "rebuilt" pump will do the same. However i do agree there are some very knowledgable people here, but they are totally guessing at the problem as am i...your slipper is very scored and non rebuildable ....it will cause your swashplate to stick as soon as you come off charge pressure...anyways as i said at the start good luck with your project...
I agree, I am leaning more toward cavitation vs contamination also. But why am I not getting ample oil back to the pumps?
I thought the tow valves got screwed IN to disable , OUT to operate??? Am I mis-remembering this important fact???
Well in my world that pump is shot...most oil would be going straight back to case...which goes right back to tank..if you can feel anything at all on plates it will go straight to case at system pressure...plus your charge pump would never keep up with that much wear....there are actually 3 circuits on a hydro pump....charge pressure ...system pressure. . And loop cooling....the sauer pumps have an internal hot oil shuttle for cooling...and the motors will too...but those pumps are so bad most of your charge pressure was going to case for sure.
Apetad, I’m no expert by any means as you can probably tell by my post, ha ha, but the owners manual states to back out valve no more than 2 turns for bypass and tighten for normal operation. The danfoss manual says same thing except no more than 3 turns. I wish it had been that easy. You had me thinking for a minute.
rondig, now that makes complete since, but how did the groves get there to begin with if that is the case? My first thought is maybe air initially in the system creating cavitation, which caused the wear, in turn lead to, well you know. My second thought, maybe contamination created wear, which caused the cavitation. But again no wear to motors...... My 3rd thought, I’m going back to when you said something about not having oil in it. When I got the pumps back in the machine and plumbed, I pulled the charge pump plug and filled the pumps there. Was that enough oil? Should I have done more? The pump had never been apart
So rereading the thread, rondig said, “If the wheels turn with the counter balance valves released and the motors are good then there was not enough oil in the loop.” So I’m thinking I should have filled the pump as I did, manually turn the tires, refill pump, and so on until I get resistance. ?????? Am I on to something or no? Are counter balance valves the same as relief valves?
I have fitted more than a few of reconditioned/exchange tandem pump assemblies to Case skid steers. With the hydraulic tank full of oil & wheels off the ground, I've never done more than start the engine & let them idle for a minute or two while looking for any leaks & then slowly work the controls to full fwd & rev - & never had any issue with cavitation or operation of the machine. The 1800 series Case machines have a very good supply of oil flow from the tank to the tandem pumps. PS - I'm not familiar with the term counter balance valves (but, I come from the land downunder where Australian lingo is used) as far as the Case hydrostatic system goes ..... I'll go out on a limb & say the service manual for the 1840 doesn't mention them either.
Wheels off the ground is the key...you never sent the tandems to system pressure to get the wheels turning...or you can fill the pump case...any piston pump...danfoss..rexroth....any brand wants the case full before start... The damage in your pictures is cavitation....if the pump was dumping to case....most of the crap will be in return filter....saving the motors..i am wondering if the charge pressure relief in the pump didnt go first..or if charge pressure was released somewhere...looking at pistons and wear plate or could have been contamination....but when you showed picture of cradle...that was the key to cavitation....cradle scored that bad pretty much only occurs when lack of charge pressure...therefore cavitation.
Well I got some news. I decided to cut the oil filter to see what may be inside. Not good. What appears to be everything from rust, to sand, to paint chips (silver, the color I painted it and yellow, the original color)!!!!! I will attach photos. Its obvious that this somehow got in there while I had the machine apart. At initial start up, I let machine idle for roughly 2-4minutes, moved the machine in reverse and then forward. When doing this it had a lot of power back and forth, but would not steer. As I moved around the garage for about 2mins, it was loosing power and has had consistent power ever since. My theory, (I could be completely wrong) or maybe just a guess, this debris was in the pump, running at idle (at first start up) it wore the pumps. When I moved the machine the pumps were wore so fluid went directly to case drain. Never made it to motors...... Your thoughts????
Man that sucks....yep pistons and wear plate got that crap and the cradle failed for no to little charge pressure....oh man your control circuit is pre filter....so you will want to check that too.
So I got the pumps back together and sitting aside until I get motors figured out. I ordered 2 rebuild kits from case for the drive motors. Figured I would go through them and clean and replace seals just to be on the safe side. My problem is that all of the seals are not in the kit. There are 2 o-rings, roughly 4” od, 3.75” id that I do not have. Am I over looking something? In my parts manual the seal kit is all that I see
I can't recall having a problem with the kits, but I have not used one for quite some time... Don't you you love it when you pay top dollar for a 'genuine' seal kit & it doesn't do what it is supposed to...... I would look get the part numbers for the missing seals & giving the dealer a call, obviously this is something CNH needs to know about.
I spoke with dealer this morning. They sent me the wrong seal kits. Apparently there is more than one for this machine
Got the other set of motor seals and they were correct. Installed everything today. Just got back from a test drive and everything works perfect!!!!!!!!!!! Now let’s just hope it holds up! I want to thank everyone on here for the assistance. I could have never pulled this off without you. I would have never been confident enough to pull this off without this site and the people on it. I will keep you posted on how it holds up. I’m going to be nervous for the first few hours. Remember not only are my hand all over the hydrostatics, but also the engine has about 20 minutes of run time. I would like to mention that I filled the pump with oil in all ports and I believe this is unnecessary (as “airman” said). Each port holds less than a cap full. Gravity from the tank supplies the pump. If this system holds up, the way I did it can save a lot of money. I pretty much lapped all parts in motors and pumps and resealed everything. It cost me less than $1000 vs the +/-$5000 for rebuilt pumps and motors. Probably not an efficient way for someone making money with a machine, but for someone like me that is just using it around the house and has time to spare. This is the way to go. (Again if it holds up, fingers crossed). I will update in a few hours of run time. Thanks again!!!!
WooHoo! Congratulations on a job well done!
You don t have to fill every port...just the case drain. I am glad to hear it is working for you.
I almost forgot to mention, I did not install new chargepump. It was very expensive and easy enough to change out without pulling pump. Just split pump in machine if needed. I am getting 450 charge pressure at wide open throttle and about 430 with both levers fully engaged
UPDATE..... Just hit 10hours of run time. Like mentioned in earlier post, I only use this around my house so it doesn’t get much use. I hope I’m not speaking too soon, but everything is working as good as the day it was put back together. Thanks again everyone
UPDATE: 72 hours. Still running strong
This link doesn't seem to work. Can you send it to me please. Trying to figure out my 1996 Case 1845C with a weak right side drive. Seems normal in reverse. Need to know where to check pump pressures.
When the thread started I was certain it would end up here, If it were mine I would get a flat thick piece of glass, some 400 grit wet emery cloth and using light oil I would first polish the brass piston cups, then figure 8 the piston block commutator area , if you watch carefully you can see when the wear areas come out, I turn the block every few turns to try to keep it as square as possible, if the brass plates were not so badly worn I would also renew them in the same fashion but as was stated they are pretty rough. I have done many of these and other hydrostat pumps in this manner with great success. An educated guess is that at some point in time drive hoses were changed with no regard to keeping the hoses and fittings spotlessly clean. I did this work in a professional shop where I worked for 50+ years and sent them out the door guaranteed. Looking back I see this is an old thread but my advice still stands for those who will be reading in the future.