M600 Drive System Problem / Question

[M600-Des]

Hi All, I'm looking for some diagnostic help with my Bobcat M600P's drive system. Symptoms: Engine runs well with the variable drive lever pulled right back (Neutral?) but when the lever is moved very slowly forward the drive suddenly engages and the engine revs drop and the engine labours very hard. If left like that the engine finally stalls. Pulling the variable speed lever back allows the engine to recover. Moving the steering levers while the drive is engaged and the engine is labouring makes the machine move backward or forward as expected. Leaving them centralised the machine doesn't move. Background: The machine has been standing unused (engine dead) for about 2 years. The engine has recently been restored and is now working well. When the machine was first started (2 days ago) it could be driven forward and backwards with the variable speed lever pulled fully back. Any attempt to engage the variable speed drive would result in engine stall. Yesterday, over a period of about 15 mins of use the maximum speed forward or backwards slowly reduced until the machine would no longer go either backwards or forwards. Engaging the variable speed drive made the engine work a little harder but it no longer stalled. Last night the machine was working well and there were no obvious signs of distress. Today, with the variable speed lever pulled right back the machine will not move backward or forward but when the variable lever is moved forward the engine labours very hard and will eventually stall. Actions taken: I have taken the right-hand drive cover off and was amazed at the immaculate condition of the housing, chains, drives etc. The oil looked brand new. As the machine is jacked up and has no wheels on the right-hand side I used a lever to turn the front wheel. This was quite hard to do but was smooth. There was a sucking, squelching sound from the oil which sounded more like grease than oil. It's minus 10c here today so maybe the oil viscosity is too thick? Moving the right-hand steering lever forward slightly while turning the wheel instantly locked the wheel solid. So based on my experience so far what is the most likely cause of my problem? Is it that the oil is too thick or could the problem be in the unchecked left-hand side? As an aside, am I correct in thinking that the two chain housings are connected? I can only find reference to one oil filler "telltale" and that's on the left-hand side. If not how much oil should be in the right-hand casing? If I have left out some vital information please ask away! Thanks, Des

 

[jerry]

the left and right chain cases are interconnected as far as oil , there are two 1/8 inch pipe plugs on the right side of machine just behind the front wheel. One is for high oil level and the other is for low. As long as the oil is up to the lower plug you are ok. The recomended oil is automatic transmission fluid . OIl of heavier viscosity would cause clutch problems in cold weather. It does sound like the oil is too thick for the temperature. Does the variable sheave open and close as it should? If you ever disassemble it be sure to put the gland back it the right way. It can be put in backwards and then the pressure will ruin it. Dredge the bottom of the chain case with a magnet also to see if you come up with small rollers from the clutch thrust bearings, one of them could have gone out also.

 

[M600-Des]

the left and right chain cases are interconnected as far as oil , there are two 1/8 inch pipe plugs on the right side of machine just behind the front wheel. One is for high oil level and the other is for low. As long as the oil is up to the lower plug you are ok. The recomended oil is automatic transmission fluid . OIl of heavier viscosity would cause clutch problems in cold weather. It does sound like the oil is too thick for the temperature. Does the variable sheave open and close as it should? If you ever disassemble it be sure to put the gland back it the right way. It can be put in backwards and then the pressure will ruin it. Dredge the bottom of the chain case with a magnet also to see if you come up with small rollers from the clutch thrust bearings, one of them could have gone out also.

Hi Jerry,
Thanks for the info. The variable sheave seems to work fine. One critical factor which I had forgotten to include in my write-up was that yesterday the Bobcat was stored in the garage at about +10c whereas today it woke up outside in -10 which would give more credence to the "wrong oil" theory!
The oil is certainly not transmission fluid, so I will change it - Is there a drain, or do I have to pump the oil out? I will look for "spare" bearings at that point.
Des​

 

[OldMachinist]

Hi Jerry,
Thanks for the info. The variable sheave seems to work fine. One critical factor which I had forgotten to include in my write-up was that yesterday the Bobcat was stored in the garage at about +10c whereas today it woke up outside in -10 which would give more credence to the "wrong oil" theory!
The oil is certainly not transmission fluid, so I will change it - Is there a drain, or do I have to pump the oil out? I will look for "spare" bearings at that point.
Des

 

[M600-Des]

Ok, now I'm going to say one of those things that makes everyone at the party suddenly go quiet and stare, followed by light snickering and then full-on laughter (including pointing):
Is the hydraulic oil the same oil that lubricates the chain cases?
Ok there ya go I said it - Let the merriment begin ;-)
Whatever the answer, thanks for taking the time to reply!

 

[jerry]

Ok, now I'm going to say one of those things that makes everyone at the party suddenly go quiet and stare, followed by light snickering and then full-on laughter (including pointing):
Is the hydraulic oil the same oil that lubricates the chain cases?
Ok there ya go I said it - Let the merriment begin ;-)
Whatever the answer, thanks for taking the time to reply!

Yes and the drain port is the one closest to the front of the machine, the other is for fuel tank, interesting things happen if you start the machine with that side cover over the clutches off.

 

[Kilroy2k1]

Yes and the drain port is the one closest to the front of the machine, the other is for fuel tank, interesting things happen if you start the machine with that side cover over the clutches off.

Check the driven pully to make sure it opens easily when the drive pully closes. Its fairly easy to check, just reach in and grab the belt in the middle and pull it up. You should be able to pull it up a good couple inches and see the driven pully spreading apart.
If the clutches are not binding then check the jackshaft bearings, it should spin with the belt as you turn the engine over by hand. I cant see it being the hydraulic portion causing the problem but as I am just getting into my 600's innards myself, anything is possible.
Tom.

 

[mahans7]

Check the driven pully to make sure it opens easily when the drive pully closes. Its fairly easy to check, just reach in and grab the belt in the middle and pull it up. You should be able to pull it up a good couple inches and see the driven pully spreading apart.
If the clutches are not binding then check the jackshaft bearings, it should spin with the belt as you turn the engine over by hand. I cant see it being the hydraulic portion causing the problem but as I am just getting into my 600's innards myself, anything is possible.
Tom.

M600, the guys here are great about answering just about anything. So if you want to know, just ask. I still ask some pretty basic questions since I'm way down on the learning curve, but they're bringing me up.

 

[M600-Des]

M600, the guys here are great about answering just about anything. So if you want to know, just ask. I still ask some pretty basic questions since I'm way down on the learning curve, but they're bringing me up.

Thanks to everyone for the info and in the spirit of inquiry I'd like to ask some more questions ;-)
The oil I have seen in the gear case was a very viscous, clear oil. My limited experience of automatic transmission oil is that it's red, but that could mean nothing. So before I start mixing hydraulic oil and transmission oil (are they different?) I'd be very grateful if someone could confirm the exact specification for the oil I should be using? I can't find any reference to it in my Service Manual.
Also, would it be correct to think that if I run the engine and work the hydraulics the oil will heat up and become thinner allowing my gears to work more easily? Or is the heating effect on the oil minimal? So many questions, so little knowledge ;-)
Thanks,
Des

 

[OldMachinist]

Thanks to everyone for the info and in the spirit of inquiry I'd like to ask some more questions ;-)
The oil I have seen in the gear case was a very viscous, clear oil. My limited experience of automatic transmission oil is that it's red, but that could mean nothing. So before I start mixing hydraulic oil and transmission oil (are they different?) I'd be very grateful if someone could confirm the exact specification for the oil I should be using? I can't find any reference to it in my Service Manual.
Also, would it be correct to think that if I run the engine and work the hydraulics the oil will heat up and become thinner allowing my gears to work more easily? Or is the heating effect on the oil minimal? So many questions, so little knowledge ;-)
Thanks,
Des

My service manual for the 600 say 10w30 engine oil for the hydraulic system.

 

[6brnorma]

Thanks to everyone for the info and in the spirit of inquiry I'd like to ask some more questions ;-)
The oil I have seen in the gear case was a very viscous, clear oil. My limited experience of automatic transmission oil is that it's red, but that could mean nothing. So before I start mixing hydraulic oil and transmission oil (are they different?) I'd be very grateful if someone could confirm the exact specification for the oil I should be using? I can't find any reference to it in my Service Manual.
Also, would it be correct to think that if I run the engine and work the hydraulics the oil will heat up and become thinner allowing my gears to work more easily? Or is the heating effect on the oil minimal? So many questions, so little knowledge ;-)
Thanks,
Des

Look under 8E-2 of your Service Manual and you will find the specs for the hydraulic system. 20 gals of 10w-30 or 10w-40 engine oil. That said I have ONLY used the cheapest NAPA tractor hydro oil in probably 25 or so different 610s for nearly 40 yrs now......reason being that it works great and I don't have a single machine that doesn't leak at least a few drops (I consider it a leak when it sprays the operator ;-)). I have additionally bought machines that the previous owner had been running auto trans fluid with no apparent ill effects. I have not responded to you "power" question due to the fact there are so many possibilities as to what the problem is. In my view, I would start by isolating two different issues. Is it a "engine power" problem or a mechanical "drag" on the engine problem. You mentioned that work had recently been performed on the engine which makes me suspicious. I have had machines that couldn't make it back onto the trailer due to something as simple as a 'timing' issue.

 

[6brnorma]

Look under 8E-2 of your Service Manual and you will find the specs for the hydraulic system. 20 gals of 10w-30 or 10w-40 engine oil. That said I have ONLY used the cheapest NAPA tractor hydro oil in probably 25 or so different 610s for nearly 40 yrs now......reason being that it works great and I don't have a single machine that doesn't leak at least a few drops (I consider it a leak when it sprays the operator ;-)). I have additionally bought machines that the previous owner had been running auto trans fluid with no apparent ill effects. I have not responded to you "power" question due to the fact there are so many possibilities as to what the problem is. In my view, I would start by isolating two different issues. Is it a "engine power" problem or a mechanical "drag" on the engine problem. You mentioned that work had recently been performed on the engine which makes me suspicious. I have had machines that couldn't make it back onto the trailer due to something as simple as a 'timing' issue.

OK......after reading your opening post a little closer. I would still double check some of the simpler engine items.....timing, governor linkage, spark gap, etc. but from what your saying I would look more seriously at hydro problems. Using my swag capabilities I would seriously wonder if your 'Master Relief' valve is not giving you problems......especially after two years of sitting. Just sounds like hydro is not flowing correctly if engine dies when operating the variable speed. Relief valve is a bit of a bugger to get to.

 

[M600-Des]

OK......after reading your opening post a little closer. I would still double check some of the simpler engine items.....timing, governor linkage, spark gap, etc. but from what your saying I would look more seriously at hydro problems. Using my swag capabilities I would seriously wonder if your 'Master Relief' valve is not giving you problems......especially after two years of sitting. Just sounds like hydro is not flowing correctly if engine dies when operating the variable speed. Relief valve is a bit of a bugger to get to.

Firstly thanks to everyone for their replies, they're all very helpful.
So here's the sequence of events that have happened since my last post:
1. Bobcat put into garage over night.
2. Bobcat started on the button and drive engaged without drama.
3. An hour or so of snow clearing undertaken without incident!
I'm sure now that the problem was "simply" very cold / thick oil. I will be topping up the system with thinner oil today,but for now the Bobcat has a nice cozy home.
All of that said I'm not convinced that the engine is timed perfectly. I have read the manual about the process and am not sure I understand it but I will make that the subject of another post.
Incidentally, my manual must be slightly different to the one shown here as mine just shows:
http://auhof.co.uk/downloads/hydraulic_oil.png
Is there a copy of this manual available anywhere as mine seems to be found wanting?
Thanks again,
Des

 

[mahans7]

OK......after reading your opening post a little closer. I would still double check some of the simpler engine items.....timing, governor linkage, spark gap, etc. but from what your saying I would look more seriously at hydro problems. Using my swag capabilities I would seriously wonder if your 'Master Relief' valve is not giving you problems......especially after two years of sitting. Just sounds like hydro is not flowing correctly if engine dies when operating the variable speed. Relief valve is a bit of a bugger to get to.

Des, as you run the engine and work the hydraulics the oil will heat up and become thinner which should allow your gears to work more easily, especially if your HO radiator is 80% clogged with dirt/mud and rocks like mine was. The heating effect on the oil is significant and a recent post here described the temp getting high enough where it was uncomfortably hot to touch the hydraulic lines. HTH

 

[M600-Des]

Des, as you run the engine and work the hydraulics the oil will heat up and become thinner which should allow your gears to work more easily, especially if your HO radiator is 80% clogged with dirt/mud and rocks like mine was. The heating effect on the oil is significant and a recent post here described the temp getting high enough where it was uncomfortably hot to touch the hydraulic lines. HTH

Yep, I'm sure you're right - It definitely got happier as things warmed up.
One thing though, you mentioned a radiator - I'm "fairly" sure I don't have such a thing on my machine. Where would I find it (kinda dumb question I know)?
Des

 

[6brnorma]

Yep, I'm sure you're right - It definitely got happier as things warmed up.
One thing though, you mentioned a radiator - I'm "fairly" sure I don't have such a thing on my machine. Where would I find it (kinda dumb question I know)?
Des

No radiator on M-600. Manuals available on e-bay most any day.