M700 hydrostatic ?

[cp7]

I just picked up an M700 that had been setting for a few years. PO said a pump was bad because the hydro was weak on one side when he parked it.

Really thought we would be in for a fight to drag it up on the trailer because we thought we would have to open a hydro line to relieve pressure to let her roll and didn't want to make a mess at the sellers place. The winch rolled her right up on the trailer with no resistance. Is that right or an indication of what may be wrong with her?

Got the Wisconsin running and the loader hydraulics work great but she is real weak on the drive (both sides) and really wants to squall like it's hitting the reliefs when you try to turn which it doesn't want to do.

Thanks very much to Old Machinist I've got the manuals and it says that to be able to move a disabled machine you need to remove the high pressure relief/replenishing valves. We pulled those out and inspected them and one was stuck but freed up pretty easy so we reinstalled them and she acts the same.

Oil is very clean and we got new filters but didn't get them put on today.
It shows how to check the charge pressure at the filter and I need to get a gauge to do that but it also shows how to check the by-pass valve with a fancy tester that I don't have. Can that by-pass valve be visually inspected for defects?

We picture and pray that something ahead of the hydrostats is at fault but we're new to this so any suggestions will be very welcomed.
Thanks guys.

 

[SkidRoe]

Definitely sounds like a motor problem to me. The machine should not roll that easy, even if the relief valves are leaking.

 

[cp7]

Definitely sounds like a motor problem to me. The machine should not roll that easy, even if the relief valves are leaking.

Thanks for the input skid.

 

[Langloim]

Thanks for the input skid.

You're by-passing in the hydrostatic drive, lap the cassettesa and wafer plates

 

[cp7]

You're by-passing in the hydrostatic drive, lap the cassettesa and wafer plates

Thanks for your input Lang but can you elaborate. Are you talking about the pump or the motor?
I'm not very versed on the piston pumps in this hydrostatic system but it looks to me that the internals are pretty much the same on the two
I've got the service manual and have been holding off tearing into the system but need to get on it.
Any and all advice will be greatly appreciated.

 

[SkidRoe]

Thanks for your input Lang but can you elaborate. Are you talking about the pump or the motor?
I'm not very versed on the piston pumps in this hydrostatic system but it looks to me that the internals are pretty much the same on the two
I've got the service manual and have been holding off tearing into the system but need to get on it.
Any and all advice will be greatly appreciated.

He is referring to the swash plates in the pumps. If it is the pumps, it will take more than lapping the swash plates to remedy this issue. I would start with the drive motors. pull them, get them checked, and rebuild them if necessary. If that doesn't fix it, I would then turn your attention to the pumps. But before doing any of that, check the charge pressure. HTH..

 

[cp7]

He is referring to the swash plates in the pumps. If it is the pumps, it will take more than lapping the swash plates to remedy this issue. I would start with the drive motors. pull them, get them checked, and rebuild them if necessary. If that doesn't fix it, I would then turn your attention to the pumps. But before doing any of that, check the charge pressure. HTH..

Thanks Skid. I did check that charge pressure and it was at 50psi.
Sounds like we'll be diving deeper into her.

 

[jerry]

Thanks Skid. I did check that charge pressure and it was at 50psi.
Sounds like we'll be diving deeper into her.

50 lb is low but doesnt explain weakness on one side. Is the oil level in the reservoir above where it should be? If the motors are ok don't be afraid to dig into the hydro pumps , just keep it clean work slowly and only on one at a time. They are simple enough and the way they work is interesting.

 

[cp7]

50 lb is low but doesnt explain weakness on one side. Is the oil level in the reservoir above where it should be? If the motors are ok don't be afraid to dig into the hydro pumps , just keep it clean work slowly and only on one at a time. They are simple enough and the way they work is interesting.

Thanks jerry,
We were told that it was weak on one side but it's really about equal on both sides. The oil level was actually high so we drained out three gallons of very clean oil to get it where it should be.

Where we stand is that we've pulled the bypass valves out and there was a couple that had the pin sticking so we got them freed up but it didn't seem to help. We bought new filters and still have yet to get them put it.
I replaced the pressure switch at the filter with a gauge and it's reading about 50psi.
I'm still praying that replacing the lower filter might bring the pressure up and help or fix it.
I wish it had the elusive screen filter like the 630 does that by cleaning magically fixes hydraulic issues.

We're junking cars and just got a model 630 a couple months ago and it doesn't have quite enough guts to do what we need but we're getting the hang of it a little better, enough to get the job done. When I saw this M700 on Clist and all he wanted was scrap weight price we jumped in the truck and went and paid for it. Since she's supposed to have another twenty percent capacity over the 630 we really want to get her going but are so busy it's been on hold.

I appreciate all of you guy's input and will need lots more if we have to tear into the pumps and motors.
Are the rotating parts in there easily fixable like langloim suggested or will they probably need to be replaced?

 

[jerry]

Thanks jerry,
We were told that it was weak on one side but it's really about equal on both sides. The oil level was actually high so we drained out three gallons of very clean oil to get it where it should be.

Where we stand is that we've pulled the bypass valves out and there was a couple that had the pin sticking so we got them freed up but it didn't seem to help. We bought new filters and still have yet to get them put it.
I replaced the pressure switch at the filter with a gauge and it's reading about 50psi.
I'm still praying that replacing the lower filter might bring the pressure up and help or fix it.
I wish it had the elusive screen filter like the 630 does that by cleaning magically fixes hydraulic issues.

We're junking cars and just got a model 630 a couple months ago and it doesn't have quite enough guts to do what we need but we're getting the hang of it a little better, enough to get the job done. When I saw this M700 on Clist and all he wanted was scrap weight price we jumped in the truck and went and paid for it. Since she's supposed to have another twenty percent capacity over the 630 we really want to get her going but are so busy it's been on hold.

I appreciate all of you guy's input and will need lots more if we have to tear into the pumps and motors.
Are the rotating parts in there easily fixable like langloim suggested or will they probably need to be replaced?

I believe the m700 was earlier than the 630 and there are differences , main one I think is that the hydraulic reservoir and the chain case are seperate on the 630 so grit from chain wear doesn't get into the hyd syster. . If your chain case was overful it is kind of a sign that a drive motor is bypassing oil into it or water leaking in. . Lots of posts here on that. The pump and motor repair also has been posted several times. Get the service manual if you want to repair them yourself and work cleanly and slowly. I have only done the pumps on a 632 and it cost only for a few sheets of emery , a relief valve spring and some o rings. In the rotating group in mine some pistons had minor chips and it still worked great when back together. Get a little guidance from Tazza and it will be a big help.

 

[Langloim]

I believe the m700 was earlier than the 630 and there are differences , main one I think is that the hydraulic reservoir and the chain case are seperate on the 630 so grit from chain wear doesn't get into the hyd syster. . If your chain case was overful it is kind of a sign that a drive motor is bypassing oil into it or water leaking in. . Lots of posts here on that. The pump and motor repair also has been posted several times. Get the service manual if you want to repair them yourself and work cleanly and slowly. I have only done the pumps on a 632 and it cost only for a few sheets of emery , a relief valve spring and some o rings. In the rotating group in mine some pistons had minor chips and it still worked great when back together. Get a little guidance from Tazza and it will be a big help.

if your machine free wheels it means the hydrostat. is acting like a pump and is able to push the fluid to low pressure, throught a groove. Once the hydrostatic wafer plates are smooth the pistons hydro-lock and the fluid can't move anywhere. if the wheels turn feelly you have by-pass wither motors or hydrostat. just open it up and clean them up you'll realizehow easy it is and you'll be thank ful later on.

 

[SkidRoe]

if your machine free wheels it means the hydrostat. is acting like a pump and is able to push the fluid to low pressure, throught a groove. Once the hydrostatic wafer plates are smooth the pistons hydro-lock and the fluid can't move anywhere. if the wheels turn feelly you have by-pass wither motors or hydrostat. just open it up and clean them up you'll realizehow easy it is and you'll be thank ful later on.

Hi langloim, I am curious: what exactly are you referring to as a "wafer plate"? Are you refering to what is commonly known as a "swash plate" This is the tiltable plate in the hydro pumps that the piston shoes run against. Or are you refering to a plate that seals the piston bores to the pump body, basically a "head gasket"?

 

[Tazza]

Hi langloim, I am curious: what exactly are you referring to as a "wafer plate"? Are you refering to what is commonly known as a "swash plate" This is the tiltable plate in the hydro pumps that the piston shoes run against. Or are you refering to a plate that seals the piston bores to the pump body, basically a "head gasket"?

The swash plate is the part that tilts to vary the amount of oil being pumped. This is where the piston shoes run on. The wafer plate/wear plate/valve plate is the part the face of the rotating group runs on. This is the side the oil is under high pressure and is directed into the valve block and goes to the drive motors.
Any scores on this plate allows the oil to by-pass and you loose drive power. Bobcat says if there are any marks that you can feel with a finger nali, it must be replaced. I have repaired a few with a sheet of glass as a flat surface and wet and dry sand paper. Keep the plate moving in all different directions as to not take more from one side than the other.

 

[cp7]

The swash plate is the part that tilts to vary the amount of oil being pumped. This is where the piston shoes run on. The wafer plate/wear plate/valve plate is the part the face of the rotating group runs on. This is the side the oil is under high pressure and is directed into the valve block and goes to the drive motors.
Any scores on this plate allows the oil to by-pass and you loose drive power. Bobcat says if there are any marks that you can feel with a finger nali, it must be replaced. I have repaired a few with a sheet of glass as a flat surface and wet and dry sand paper. Keep the plate moving in all different directions as to not take more from one side than the other.

Jerry my 630 runs great, I'm needing to get the M700 fixed.
I do have a service manual for each one of them but they want you to replace parts instead of repairing.

Lang you sound allot like my brother. He'll tear into it and figure it out, me I prefer to have an idea of what I'll be getting into.
Taz thanks for joining in. I've read a few of your old posts.

In reading old threads I still don't know which we need to tear into first, the motors or pumps.
I'm also wondering about these plates. In looking at the parts manual they look like they remove from what's listed as the yoke.
Are they not machined on both sides so that you could just flip it over and have a fresh clean surface? I know that's to simple but had to ask.
Can just the swash plate be bought new?

 

[Langloim]

Jerry my 630 runs great, I'm needing to get the M700 fixed.
I do have a service manual for each one of them but they want you to replace parts instead of repairing.

Lang you sound allot like my brother. He'll tear into it and figure it out, me I prefer to have an idea of what I'll be getting into.
Taz thanks for joining in. I've read a few of your old posts.

In reading old threads I still don't know which we need to tear into first, the motors or pumps.
I'm also wondering about these plates. In looking at the parts manual they look like they remove from what's listed as the yoke.
Are they not machined on both sides so that you could just flip it over and have a fresh clean surface? I know that's to simple but had to ask.
Can just the swash plate be bought new?

the wafer/swash plate depending on who you talk to. These plates are locate against the valve block, non-rotational plates and held in place with a locating pin. These plates are a combo of steel and brass (steel against the valve body and brass for the the cassette). These plates aren't machined they're optically lapped for true flatness if you machine them you're waste your time you'll need to achieve a R8 surface finsih, turning will give you at best a R63 surface finishess. To purchase the plates they're about $250 a piece depending on the supplier, some cheaper some more. If you lap the plates with diamond lapping compound for a smooth finish you'll resolve alot of the issues. Just make sure what you lap against is truly flat use a grainite surface table for the truest flatness. I'm speaking from my trade as a machinist

 

[Tazza]

the wafer/swash plate depending on who you talk to. These plates are locate against the valve block, non-rotational plates and held in place with a locating pin. These plates are a combo of steel and brass (steel against the valve body and brass for the the cassette). These plates aren't machined they're optically lapped for true flatness if you machine them you're waste your time you'll need to achieve a R8 surface finsih, turning will give you at best a R63 surface finishess. To purchase the plates they're about $250 a piece depending on the supplier, some cheaper some more. If you lap the plates with diamond lapping compound for a smooth finish you'll resolve alot of the issues. Just make sure what you lap against is truly flat use a grainite surface table for the truest flatness. I'm speaking from my trade as a machinist

The last lot of plates i got were $58 each, far cheaper than the dealer!
The yoke is the swash plate, it just tilts back and forth.
These parts are in the pump and not motor. It's really hard to say what part to dive into first. I would start with the pump as over time they always get marks on the wear surfaces. Just keep all parts for each pump seperate. Never mix them up, do one side at a time to ensure it's all ok. The wear plates may look the same, they are not.
I have touched up a few pumps with marks in the wear plates before with good results after flattening them.
Langloim - how do you diamond lap the sufraces? what do you use as a flat surface to use the compound on to run the wear plates over? i figured it would wear down and not be flat for long. That's why i use wet and dry on a sheet of glass for my flat surface.

 

[Langloim]

The last lot of plates i got were $58 each, far cheaper than the dealer!
The yoke is the swash plate, it just tilts back and forth.
These parts are in the pump and not motor. It's really hard to say what part to dive into first. I would start with the pump as over time they always get marks on the wear surfaces. Just keep all parts for each pump seperate. Never mix them up, do one side at a time to ensure it's all ok. The wear plates may look the same, they are not.
I have touched up a few pumps with marks in the wear plates before with good results after flattening them.
Langloim - how do you diamond lap the sufraces? what do you use as a flat surface to use the compound on to run the wear plates over? i figured it would wear down and not be flat for long. That's why i use wet and dry on a sheet of glass for my flat surface.

Tazza where did you get plates for $58 dam that's cheap I got my price from bobcat. For your diamond question it's diamond lapping compound you can get from 1000 course to extra fine of 6000 grit. It's used for optical flat surfaces alot of times in valve seats. I wouldn't waste my time on anything over 1500 grit this will give a flat surface. Just wash with a parts cleaner when finished and you'll find they'll last longer being true flat.

 

[Langloim]

Tazza where did you get plates for $58 dam that's cheap I got my price from bobcat. For your diamond question it's diamond lapping compound you can get from 1000 course to extra fine of 6000 grit. It's used for optical flat surfaces alot of times in valve seats. I wouldn't waste my time on anything over 1500 grit this will give a flat surface. Just wash with a parts cleaner when finished and you'll find they'll last longer being true flat.

Forgot to add I use a layout table or a frosting plate. These are true flat better then glass cause glass can have a wave in it due to the manufacturing process. Glass is made on a bed of liquid tin so it can have a wave in it.

 

[cp7]

Forgot to add I use a layout table or a frosting plate. These are true flat better then glass cause glass can have a wave in it due to the manufacturing process. Glass is made on a bed of liquid tin so it can have a wave in it.

Yea Taz, $58 sounds pretty good. Where can they be had for that?
From the parts book exploded views it sure looks like the guts of the pump and motor on the M700 are very similar with both having the rotating groups.


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