My MD70 seems to sometime loose all drive power to both tracks. If im pushing into a dirt pile or up a steeper grade sometimes I just loose most of the forward drive power. The tracks will try to slowly go forward but with very minimal power. The engine does not bog down at all. Normally I just reverse which works fine and then go forward and all is good. Today I was on the edge of a very steep hill and I lost reverse drive power. I could go forward fine, just didnt really want to. Turned the engine off and on, no difference. Dropped the grapple into the ground and spun the tracks forward fine. Just couldnt get any reverse power. Eventually I got enough to get away from the clff and then all drive power came back. I am wondering if this could be a relief valve popping open and sticking. When driving most of the time I can load up the engine when pushing slowly. This seems to be more if I load up the tracks more suddenly. Sometimes Forward or reverse I just loose power, put the controls to neutral and then slowly give it drive power and it works fine. The problem does seem to be getting slowly worse. I am going to soon have the tank open to change out the bucket hydraulic pump and am looking at what to check in there on the drive pump.
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Thought I figured it out as being a dirty filter on the drive pump. The drive definitly had more power but then once running warmer a couple hrs later i slowly lost drive power. I am wondering if I am even running the correct oil. This definitly seems to be a heat related issue even though its not that warm here yet. (20C) Previous owner said he just used standard aw 46 found everywhere. I found an oil reference in the parts book and it says Amocco Rycon MV. this oil then crosses eventually to an aw32. Im going to have to check into this further. Does anyone know what this Rycon MV crosses to in current oils?
Update I got the oil crossed to a chevron equivalent and swapped out the oil. The drive seemed to work fine and then as the loader was used for an hour it lost drive power. Increasing the RPM slightly will get it moving again but then it fades away. At the end it needed almost full RPM to move at all. I checked the oil temp and it was 46C out of the cooler. Thats not too hot in my opinion. I left the machine to cool over night and today it drove but faded really fast. Even cold it didnt have much power. How does one test the pressure on these pumps? Its a sauer sundstrand M91-46672 MPT046C I looked at the pressure regulator and it doesnt seem to be passing. I unhooked the outlet and nothing was flowing out when under load. Heres the pump https://drive.google.com/file/d/0BwBL34qhDtojRUxFRDBmYXhQalk/view?usp=sharing Heres the pump tag https://drive.google.com/file/d/0BwBL34qhDtojeHhkbmdWRmdOZnc/view?usp=sharing Any info is appreciated, even some ideas that may work on other brands as they are all basically the same. I am suspecting that maybe the drive pump is worn and needs a rebuild. Are these difficult to rebuild? thanksThought I figured it out as being a dirty filter on the drive pump. The drive definitly had more power but then once running warmer a couple hrs later i slowly lost drive power. I am wondering if I am even running the correct oil. This definitly seems to be a heat related issue even though its not that warm here yet. (20C) Previous owner said he just used standard aw 46 found everywhere. I found an oil reference in the parts book and it says Amocco Rycon MV. this oil then crosses eventually to an aw32. Im going to have to check into this further. Does anyone know what this Rycon MV crosses to in current oils?
Could it be worn steering linkages?Update I got the oil crossed to a chevron equivalent and swapped out the oil. The drive seemed to work fine and then as the loader was used for an hour it lost drive power. Increasing the RPM slightly will get it moving again but then it fades away. At the end it needed almost full RPM to move at all. I checked the oil temp and it was 46C out of the cooler. Thats not too hot in my opinion. I left the machine to cool over night and today it drove but faded really fast. Even cold it didnt have much power. How does one test the pressure on these pumps? Its a sauer sundstrand M91-46672 MPT046C I looked at the pressure regulator and it doesnt seem to be passing. I unhooked the outlet and nothing was flowing out when under load. Heres the pump https://drive.google.com/file/d/0BwBL34qhDtojRUxFRDBmYXhQalk/view?usp=sharing Heres the pump tag https://drive.google.com/file/d/0BwBL34qhDtojeHhkbmdWRmdOZnc/view?usp=sharing Any info is appreciated, even some ideas that may work on other brands as they are all basically the same. I am suspecting that maybe the drive pump is worn and needs a rebuild. Are these difficult to rebuild? thanks
To check the pressure, you can remove the lines to the motor and install a 5,000PSI gauge and see what you get when operating the steering lever.
It could be a bad relief valve i guess in the pump, but if the issue is for both motors in both directions, it would be unlikely.
I checked both steering linkages ontop of the pump and they do go full lock to lock. Ill grab some fittings and go check the pressures. Seems almost like the pump wont put out enough unless the engine is reved right up. I did a little research and it looks like there might be pressure test ports on the pump and a couple internal reliefs that can be pulled out. Maybe an oring or spring is broke. I dont know much about these drive pumps. At idle the tracks just turn vey slightly. I have to now go past 2500rpm to get them to turn at all.Could it be worn steering linkages?
To check the pressure, you can remove the lines to the motor and install a 5,000PSI gauge and see what you get when operating the steering lever.
It could be a bad relief valve i guess in the pump, but if the issue is for both motors in both directions, it would be unlikely.
It sounds like it could be a worn pump...I checked both steering linkages ontop of the pump and they do go full lock to lock. Ill grab some fittings and go check the pressures. Seems almost like the pump wont put out enough unless the engine is reved right up. I did a little research and it looks like there might be pressure test ports on the pump and a couple internal reliefs that can be pulled out. Maybe an oring or spring is broke. I dont know much about these drive pumps. At idle the tracks just turn vey slightly. I have to now go past 2500rpm to get them to turn at all.
There will be relief valves, but there should be 4, one for each high pressure line. One could break to effect one direction on one side only, but for all 4 to go at the same time? i don't like those odds, but it could happen.
If you can get a gauge on and see what pressure your pump is putting out, that would be a good start.
Depending on the pump model, you may get away with facing the wear plates inside. Deal with that if you need to.
With the pressure test, don't just ram the levers forward with the lines plugged, go slowly and feel for resistance in the levers indicating you are getting pressure and it's fighting you a little. The enging will start to bog down as it builds up pressure too.
I did some testing so far. I tested the charge pressure and when cold I got 250psi and idle and 350psi at about 2000 rpm. I moved a bit of dirt to warm up the system and about 30 mins later I was loosing drive power again. Tested the charge pressure and got about 100psi on idle and 175 psi at 2000rpm. If I engaged the drive then the pressure dropped 50psi more. I pulled and checked the charge pump relief and all looked good. I then pulled the bypass valve and found the seating area was pitted up some. It wasnt really bad but might be enough. I am also suspecting the charge pump may be bad. I am taking the pump to a semi local hydraulic shop for a look and to see about parts. This problem has been ongoing since I bought the machine except it is now way worse. I never did get the pressure to the motors checked. I dont have the fittings / hoses and the track/suspension is in the way to hook to the original hose. Ill see what I find out tomorrow at the shop.It sounds like it could be a worn pump...
There will be relief valves, but there should be 4, one for each high pressure line. One could break to effect one direction on one side only, but for all 4 to go at the same time? i don't like those odds, but it could happen.
If you can get a gauge on and see what pressure your pump is putting out, that would be a good start.
Depending on the pump model, you may get away with facing the wear plates inside. Deal with that if you need to.
With the pressure test, don't just ram the levers forward with the lines plugged, go slowly and feel for resistance in the levers indicating you are getting pressure and it's fighting you a little. The enging will start to bog down as it builds up pressure too.
It is possible the charge pump is the issue, some setups have a dedicated charge pump, others use the main hydraulic pump as a charge pump as well. I don't know what the charge pressure on that model should be, as it is a tracked machine, it may need to be in the 300 or sp PSI range that you had when cold.I did some testing so far. I tested the charge pressure and when cold I got 250psi and idle and 350psi at about 2000 rpm. I moved a bit of dirt to warm up the system and about 30 mins later I was loosing drive power again. Tested the charge pressure and got about 100psi on idle and 175 psi at 2000rpm. If I engaged the drive then the pressure dropped 50psi more. I pulled and checked the charge pump relief and all looked good. I then pulled the bypass valve and found the seating area was pitted up some. It wasnt really bad but might be enough. I am also suspecting the charge pump may be bad. I am taking the pump to a semi local hydraulic shop for a look and to see about parts. This problem has been ongoing since I bought the machine except it is now way worse. I never did get the pressure to the motors checked. I dont have the fittings / hoses and the track/suspension is in the way to hook to the original hose. Ill see what I find out tomorrow at the shop.
Mine has a dedicated gear pump for charge flow. I dropped the pump assembly off today and got a call a few hours later that the charge pump is shot and the housing for it is also bad. Apparently the seats for the bypass valves is the housing and they worn. They are going to look into the system further to see what else is bad or if anything is good and give me a cost to repair. Hopefully I can get out with a couple thousand dollar bill or less. I think a new assembly (charge and 2 drive pumps) is about 6-8 thousand when I looked around.It is possible the charge pump is the issue, some setups have a dedicated charge pump, others use the main hydraulic pump as a charge pump as well. I don't know what the charge pressure on that model should be, as it is a tracked machine, it may need to be in the 300 or sp PSI range that you had when cold.
I guess it's good to know what is bad, hopefully they can work out a repair that is cheap for you.Mine has a dedicated gear pump for charge flow. I dropped the pump assembly off today and got a call a few hours later that the charge pump is shot and the housing for it is also bad. Apparently the seats for the bypass valves is the housing and they worn. They are going to look into the system further to see what else is bad or if anything is good and give me a cost to repair. Hopefully I can get out with a couple thousand dollar bill or less. I think a new assembly (charge and 2 drive pumps) is about 6-8 thousand when I looked around.
Well it came back as something is wrong with everything. I was quoted $4000 for a replacement with 6-8 weeks delivery at the best or they rebuild mine for $4800 in a week. Found Loaderpart source has one for $1900 plus shipping both ways after core plus the great us/can exchange rate.I guess it's good to know what is bad, hopefully they can work out a repair that is cheap for you.
Im going to get mine back and look over it after talking to a hydraulic guy at work. We cant believe something is wrong with all 3 pumps as it does work when cold. He figures I might be able to do some work to the charge pump as thats the only common part between both tracks. The rest of it might not be to 100% spec but might get by for now (using it to build my house). Im not looking for 100% pump power just not only working for 30 mins in the morning.
It could be the wear plates i guess. If it has wear plates, you can use sand paper and glass to flatten them again. Talk it over with your hydraulic mate, he may be able to repair it for you cheaply.Well it came back as something is wrong with everything. I was quoted $4000 for a replacement with 6-8 weeks delivery at the best or they rebuild mine for $4800 in a week. Found Loaderpart source has one for $1900 plus shipping both ways after core plus the great us/can exchange rate.
Im going to get mine back and look over it after talking to a hydraulic guy at work. We cant believe something is wrong with all 3 pumps as it does work when cold. He figures I might be able to do some work to the charge pump as thats the only common part between both tracks. The rest of it might not be to 100% spec but might get by for now (using it to build my house). Im not looking for 100% pump power just not only working for 30 mins in the morning.
All three could be toast if metal was to get in there, it can quickly eat things up but it doesn't sound like you have major damage to the pumps.
I got the pump back and i'm not to worried about most of it. The 2 axial piston pumps look fine to me, no scoring. Both the end bearings are bad. One has lots of friction to rotate and one has a little play. They look standard are cheap to get. The gerotor pump looks terrible. The rotor it self has only very fine, barely can feel it marks. The wearing side of the pump is the casing and has deep wearing, im suprised there is no wear plate. Can the cast steel, im assuming it is, casing be welded up and milled down or is this not worth it. Its close to $3000 for a replacement pump. Im close to just ordering a new pump.It could be the wear plates i guess. If it has wear plates, you can use sand paper and glass to flatten them again. Talk it over with your hydraulic mate, he may be able to repair it for you cheaply.
All three could be toast if metal was to get in there, it can quickly eat things up but it doesn't sound like you have major damage to the pumps.
A small update. I have a machine shop here cleaning up the casing of the scoring by the gerotor pump. They are going to remove some material on a lathe to make it all uniform again and then make up a spacer on the back of the housing to make up what was removed. This will move the gerotor assembly over a very slight bit but that shouldnt matter any. I am going to wet sand the valve plates a bit to remove the slight scoring on them. The scores are just into the brass but not through. The barrels Im also going to work them a bit but they wont take very much. Now I just need to get a gasket/seal kit and I should be home free. Also replacing all the filters. Im not to sure how to purge the system out though. I cant really remove the drive motors as I have to take the entire suspension apart to get them out. Most of this damage looks like years of wear that finally took its toll. Im going to flush out what I can with some fresh oil and then go from there. Any other suggestions on things to clean or watch out for?I got the pump back and i'm not to worried about most of it. The 2 axial piston pumps look fine to me, no scoring. Both the end bearings are bad. One has lots of friction to rotate and one has a little play. They look standard are cheap to get. The gerotor pump looks terrible. The rotor it self has only very fine, barely can feel it marks. The wearing side of the pump is the casing and has deep wearing, im suprised there is no wear plate. Can the cast steel, im assuming it is, casing be welded up and milled down or is this not worth it. Its close to $3000 for a replacement pump. Im close to just ordering a new pump.
Nothing else comes to mind, interested to hear how well the machine shop went with the work they are doing.A small update. I have a machine shop here cleaning up the casing of the scoring by the gerotor pump. They are going to remove some material on a lathe to make it all uniform again and then make up a spacer on the back of the housing to make up what was removed. This will move the gerotor assembly over a very slight bit but that shouldnt matter any. I am going to wet sand the valve plates a bit to remove the slight scoring on them. The scores are just into the brass but not through. The barrels Im also going to work them a bit but they wont take very much. Now I just need to get a gasket/seal kit and I should be home free. Also replacing all the filters. Im not to sure how to purge the system out though. I cant really remove the drive motors as I have to take the entire suspension apart to get them out. Most of this damage looks like years of wear that finally took its toll. Im going to flush out what I can with some fresh oil and then go from there. Any other suggestions on things to clean or watch out for?
Well finally got all the proper parts and everything assembled. Total cost under $1000. Cheapest replacement was just over $3000. Full gasket/seal/oring set, and 2 new valve plates. Got the casing machined out and it was done perfectly. They took out .06" and made a cast spacer plate the same to move the gerotor pump over and take up the space. I finally got the pump installed and it seems to work fine. I cant believe the pushing power increase. I can finally actually make the engine work. I havent had this much power since Ive owned the machine. One issue I am having is the controls are very sensitive. Adjusting for neutral is difficult. I have it set and then if the lever doesnt snap back perfectly it creeps forward or back. Im going to put a few hours on it and see what adjustments to make.Nothing else comes to mind, interested to hear how well the machine shop went with the work they are doing.
Glad it worked out so well, nothing like a tidy up of a drive pump to restore power. Even a little wear can reduce the power a lot.Well finally got all the proper parts and everything assembled. Total cost under $1000. Cheapest replacement was just over $3000. Full gasket/seal/oring set, and 2 new valve plates. Got the casing machined out and it was done perfectly. They took out .06" and made a cast spacer plate the same to move the gerotor pump over and take up the space. I finally got the pump installed and it seems to work fine. I cant believe the pushing power increase. I can finally actually make the engine work. I havent had this much power since Ive owned the machine. One issue I am having is the controls are very sensitive. Adjusting for neutral is difficult. I have it set and then if the lever doesnt snap back perfectly it creeps forward or back. Im going to put a few hours on it and see what adjustments to make.
As for neutral, most machines are like this, they always have a little creep happening.
Nothing like having some horsepower. I keep stalling it out now. Have to get used to how it operates now. I guess the neutral was easy to find before since the pump was worn out and you had to move the sticks along ways to move. I guess ill have to fix the parking brake so the machine doesnt drive off without me.Glad it worked out so well, nothing like a tidy up of a drive pump to restore power. Even a little wear can reduce the power a lot.
As for neutral, most machines are like this, they always have a little creep happening.
