Ive got a 70s model 632 melroe bobcat that ive somehow squired , one of those you fix it you can use it deals. Ive got the engine running strong and the bucket and arms are working good but the controls are jerky as h*ll. Sometimes you turn on the engine and it wants to go forward even if you aren't pushing the controls. As far as linkage is concerned it seems to be adjusted correctly just some valves are sticking, the question is what valves. I hate to tear into something blindly so does anyone have any info on this thing? A picture of what its supposed to look like under the seat would be a start. Right now this thing isnt safe for anyone to operate as far as im concerned. From what i can tell im not the first shade tree mechanic to work on this thing, all of those pesky sensors like pressure,temp,etc have been removed by someone. The main distribution block valve isnt mounted to anything its just tucked under the seat. Any help would be appreciated.
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Firstly, if it moves without the levers being moved, the adjustment is not rite.
http://users.tpg.com.au/tazza_/Steering Adjustment.jpg
Now, ensure ALL the bushings between the levers and pump are in good shape, there should be no movement inside them. Same with the linkages on the pump. There are keyed shafts, so they should be ok, just check them all the same.
Can you take any pictures of the block you are talking about? There should be a large square block on the top of the pump with 3 hoses coming in on the left. Behind the middle fitting is a filter, remove it and clean or replace it. Not many people know its there and its not cleaned, it causes drive power issues.
If you can get pictures, that would make it much easier to give details.
http://users.tpg.com.au/tazza_/Steering Adjustment.jpg
Now, ensure ALL the bushings between the levers and pump are in good shape, there should be no movement inside them. Same with the linkages on the pump. There are keyed shafts, so they should be ok, just check them all the same.
Can you take any pictures of the block you are talking about? There should be a large square block on the top of the pump with 3 hoses coming in on the left. Behind the middle fitting is a filter, remove it and clean or replace it. Not many people know its there and its not cleaned, it causes drive power issues.
If you can get pictures, that would make it much easier to give details.
when you replace the linkage bushings also replace the support bearings on the ends of the lever shaft. A little wear on each of those parts makes a lot of difference.
The linkage does have a little slop in it and need some adjusting but i really dont think its my problem. For example say im trying to move forward and i push on the controls, then i want to go backwards so i pull back , i still end up going forward for a few seconds then bam it goes backwards ( bucks like a bull ) i took a picture of the valve i was talking about , there are two sides that have three ports im assuming you are saying the filter is behind the middle one on the side that has three hoses connected not the one that has the sensor and pressure gauge. hey how do you attach a photo here?
That is not right at all, I have a picture from my 632, I will try to post it again later. If you put a e-mail in your profile I can send it to you. Jerry
I put a picture in the media section under 632 pump, some of the hoses are disconnected and it doesn't show the linkage but it may help. I,ll try to find something in the book that will help.
from looking at the picture i can see that the sensor is at least in the right place, i think the block valve is actually upside down on mine and not mounted of course.Looking at the picture i see a large black house going under the valve does that connect on the bottom and have a t in line with it? In my pic you may notice the fittings for the large hose going into the block has been re sized im assuming do to cost and availability and that may be why the valve is upside down. Also in your pic on the side that the sensor is on i the port on the far left is that another sensor? on mine they have plumed up a pressure gauge and a bleeder like the shradder valve on a car tire. The filter that was mentioned earlier it would be on the left hand side in the pic in the middle port if im understanding correctly (am i right?) With the hoses disconnected its kinda hard for me to look at the pic and trace them back to where they tie in. Also this may just be adding more confusion to the mix but i see the linkage is disconnected but i dont see the two top mounted controls that the main bar that the linkages connect to. ( the one the centering bolt sticks out of ) Also to make matters even confusing i noticed that bar im talking about has been cut in half on mine and overlapped a half an inch and then rewelded together. I may have bit off more then i can chew on this one.
im even more confused i just went out and looked at my setup versus the one in this pic and in your pic the house right next to the sensor looks like it runs under the valve then to the back side of the transmission, ( the fitting in the middle at the backside of the pic ) now on mine the same hose runs to the right side of the transmission. Where there multiple setups for this model? maybe mine is an older one as i have no hose or fitting that i can see going to the top of the transmission, and your linkages look like they hook into the side of the transmission versus a bar on the top like mine does.
That hose goes from the hydraulic charge pump back to the hydrostatic pump. I have the service manual for 630,631and 632 and they are all the same routing and pumps. What you call the transmission is actually 3 hyd pumps, 2 variable flow piston and up front a vane type pump to feed the piston pumps and operate the cylinders. The book does not list any other variation. Can you get a good overhead picture of the whole setup? Try to include the linkage also. I can't get any better pictures of it as I no longer have the machine, these are just pics I took when reworking the hydrostatic pumps. There are others on this forum with this machine though.
There was only one as far as i was aware. Yes, there is a pipe going from the block to the top of the main pump, this supplies your charge pressure. What pressure does the gauge read when the engine is running?
I have put another picture in the media album 632 hopefully Tazza will come by and move it over here. It is the only one I could find quick in the book. It is too late today for me to learn that process.
Edited by OldMachinist to add image
I know there is a little difference in the port block in that mine had a tube coming out between the sensors but right now that is small potatoes.
Well i didnt have my camera last night to get a full overhead shot but here is one i had already had taken that shows the linkage and a little of the valve.The term tranny was for lack of a better term , in the picture jerry posted i can see how the setup is supposed to look but whats really confusing me is on the top unit i dont see the shafts that stick out and connect to the linkages for actuating the drives. As for the pressure reading on the gauge i get nothing but i think the gauge is busted and i can tell it obviously wasnt oem since it goes to 15,000 psi.
Well i didnt have my camera last night to get a full overhead shot but here is one i had already had taken that shows the linkage and a little of the valve.The term tranny was for lack of a better term , in the picture jerry posted i can see how the setup is supposed to look but whats really confusing me is on the top unit i dont see the shafts that stick out and connect to the linkages for actuating the drives. As for the pressure reading on the gauge i get nothing but i think the gauge is busted and i can tell it obviously wasnt oem since it goes to 15,000 psi.
oops i went back to edit my post to make it the correct pic and somhow i double posted one with the right pic one with the wrong pic. Sorry
How far are you from a Bobcat dealer? The parts guys I have dealt with are very helpful and can look at that picture and see what it is. Is it possible someone put a pump system in from another type machine? How big is your investment in this machine? I am thinking you may have to change a few things in there to make it operate good. Using salvage parts and your own time it may be worth it. My 632 was very smooth operating and quiet after many hours of my time and minimal cost. In our area in good condition they are asking about $6000 for a 632 but I don't think they are getting over $5000 if that. good luck Jerry
