Looking to buy a Bobcat 743 that has drive issues

[gatorguy]

Hi there, Looking for some advice here. I am looking at bobcat 743 that starts up and runs, when i take the oil fill cap off and place it on the threads it jumps around a little but not out of the whole, is thi too much blowby? Smoked on start up (hadnt been started for months) but cleared up. hour meter says 1200 hrs and isnt smashed. not sure if that is true or not. So engine wise im thinking im ok. the lift and tilt works fine, no leaking seals. However, its doesent drive on one side. I went there thinking it was a drive motor which is easily replaceable. Maybe thats all it is. but when i am even standing outside the machine with the bobcat sitting still and levers in neutral position the hydraulics will squeal. This makes me wonder if it is more than just a drive pump? When i push forward or back on the levers it feels like its fighting itself...almost like trying to drive a hydrostatic transmission with the brake on(but its not). Any insight on what these symptoms lead to? I dont mind a project but i want to know what im getting into if its going to be thousands in hydraulic pump, valve body, drive motor, etc. What would this machine be worth? Appreciate it in advance! gatorguy

 

[gatorguy]

Here are the pictures of it. Needs new tires as well. https://drive.google.com/drive/folders/1QC0yuyZlSdvfzGpMY32zrUmpXFk0p-zB?usp=sharing

 

[flyerdan]

Here are the pictures of it. Needs new tires as well. https://drive.google.com/drive/folders/1QC0yuyZlSdvfzGpMY32zrUmpXFk0p-zB?usp=sharing

If the lift and tilt work, that means that the tandem pumps are rotating, and the engine seems fine; the oil cap flutter in that test is normal.
Can you raise the rops and look at where the steering linkages connect to the pumps? Sometimes the aluminum bars will wallow out on the square shaft and not engage for steering. Just a guess, and an easy thing to check.
Since nothing has grenaded on it, if you can buy it right it might be not that bad of a project.
Hopefully someone will be along shortly with some definitive info.

 

[gatorguy]

If the lift and tilt work, that means that the tandem pumps are rotating, and the engine seems fine; the oil cap flutter in that test is normal.
Can you raise the rops and look at where the steering linkages connect to the pumps? Sometimes the aluminum bars will wallow out on the square shaft and not engage for steering. Just a guess, and an easy thing to check.
Since nothing has grenaded on it, if you can buy it right it might be not that bad of a project.
Hopefully someone will be along shortly with some definitive info.

Thanks for the reply. Maybe I can check that if i go back there with a trailer to buy it but i have a hunch its more than that. So does the lift/tilt working eliminate the hydraulic pump as being an issue? Besides maybe the micron filter? Just want to have some idea before pulling the plug. Id try to rebuild pumps before buying but im pricing this out as worst case scenario which buying cheapest reman parts available could be $5k. Also, i see these only come with like a 55" bucket or something. Would a 72"-96" bucket be too big for this machine for clearing a couple inches of snow? What about a 72" for general purpose as well? Thanks!

 

[bobbie-g]

Thanks for the reply. Maybe I can check that if i go back there with a trailer to buy it but i have a hunch its more than that. So does the lift/tilt working eliminate the hydraulic pump as being an issue? Besides maybe the micron filter? Just want to have some idea before pulling the plug. Id try to rebuild pumps before buying but im pricing this out as worst case scenario which buying cheapest reman parts available could be $5k. Also, i see these only come with like a 55" bucket or something. Would a 72"-96" bucket be too big for this machine for clearing a couple inches of snow? What about a 72" for general purpose as well? Thanks!

Well, I'm the wrong guy to advise with any credibility. I usually buy expensive junk, fix it up, and sell it cheap. :-(

Bucket size: that machine has a load rating of 1300 lbs. Tipping weight is usually twice that. For a few inches of snow, I doubt you can overload even a 96" bucket unless you start to get it full. Dirt of course is a different story. 72" is too wide to handle much dirt at all; doing wood chips for landscaping, etc. would be OK.

Good luck! ---Bobbie-G

 

[flyerdan]

Well, I'm the wrong guy to advise with any credibility. I usually buy expensive junk, fix it up, and sell it cheap. :-(

Bucket size: that machine has a load rating of 1300 lbs. Tipping weight is usually twice that. For a few inches of snow, I doubt you can overload even a 96" bucket unless you start to get it full. Dirt of course is a different story. 72" is too wide to handle much dirt at all; doing wood chips for landscaping, etc. would be OK.

Good luck! ---Bobbie-G

What I'm thinking is that having hydraulics for lift and tilt means that the engine is driving all the pumps, as the hydraulic pump is at the end of the line. Since one side will drive, that means that it's getting charge pressure.
It's possible that one of the drive chains has a problem and balled up, that will bind up one whole side as both wheels are ganged. If the pumps don't sound like a cement mixer full of bowling balls, there probably isn't major component damage there.
The whine, (or squeal) as you stand beside it could be a steering lever slightly out of neutral adjustment trying to drive a motor that has a bound chain, that would be like fighting a parking brake.
You might want to grab one of the 743 books from the manual thread and have a look. They have some troubleshooting charts to help diagnose, as well as giving a good idea of how things work.

 

[gatorguy]

What I'm thinking is that having hydraulics for lift and tilt means that the engine is driving all the pumps, as the hydraulic pump is at the end of the line. Since one side will drive, that means that it's getting charge pressure.
It's possible that one of the drive chains has a problem and balled up, that will bind up one whole side as both wheels are ganged. If the pumps don't sound like a cement mixer full of bowling balls, there probably isn't major component damage there.
The whine, (or squeal) as you stand beside it could be a steering lever slightly out of neutral adjustment trying to drive a motor that has a bound chain, that would be like fighting a parking brake.
You might want to grab one of the 743 books from the manual thread and have a look. They have some troubleshooting charts to help diagnose, as well as giving a good idea of how things work.

I see what your saying. I took a look at all the manuals for it (what a treasue trove!) and i see how its the end of the line as you say so hopefully isolated to the drive/chain/etc. I think ill pull the plug on it. Will let you know how it goes next week if i can get out there to make a deal. Thanks, Have a great rest of the weekend!

 

[Lowe.Buuck]

I see what your saying. I took a look at all the manuals for it (what a treasue trove!) and i see how its the end of the line as you say so hopefully isolated to the drive/chain/etc. I think ill pull the plug on it. Will let you know how it goes next week if i can get out there to make a deal. Thanks, Have a great rest of the weekend!

You can do a quick check of the chains without draining the chain case.
Jack up a wheel and try to turn it by hand. You should be able to turn it a small amount in both directions. (You are taking the slack out of the chain.) It is normal for the wheel tread to move a couple inches.
Check each wheel.
If the wheel will not turn at all then the axle is seized or the chain has broken and is bound up on the sprocket.
If the wheel freely spins then the chain is broken, off the sprocket or sprocket is no longer connected to the shaft.
Note: If the loader had rubber over the tire tracks, manufacturers recommend that the front drive chains be removed. Since this style tracks are run without slack, the front wheels are allowed to run free to prevent drive chain and sprocket wear from the tires not turning at the exact same speed due to tire size differences.

 

[gatorguy]

You can do a quick check of the chains without draining the chain case.
Jack up a wheel and try to turn it by hand. You should be able to turn it a small amount in both directions. (You are taking the slack out of the chain.) It is normal for the wheel tread to move a couple inches.
Check each wheel.
If the wheel will not turn at all then the axle is seized or the chain has broken and is bound up on the sprocket.
If the wheel freely spins then the chain is broken, off the sprocket or sprocket is no longer connected to the shaft.
Note: If the loader had rubber over the tire tracks, manufacturers recommend that the front drive chains be removed. Since this style tracks are run without slack, the front wheels are allowed to run free to prevent drive chain and sprocket wear from the tires not turning at the exact same speed due to tire size differences.

Ok, so I finally picked it up and its in the backyard. After a quick pressure wash with all the covers and arms still down(my excuse for dirt still being around ), I took the cover off the steering linkage as it felt way too sloppy. I noticed that the centering spring was hanging loose. The levers are very sloppy and so that all needs rebuilt and adjusted I think. Next, I jacked it up with an axle stand on each axle as well as pulling the wheels and the side cover for the drive motor off. I started it up and played around with it for a bit. Up on jackstands i cant really tell a difference. The wheels went forward and back in either direction. But in different positions it would make really bad sounds, and pulling back hard on the right side felt like it was fighting itself. Whether "driving" or finding neutral and trying to hold the floppy handles there it would make squealing sounds at a minimum. I stuck my head in there and it sure sounds like it coming from the pump. The right side, red warning light is on which indicates...low charge pressure? So any tests i should do or just yank this motor out and tear it apart to look for some blown seals or something? I am quite confident all the sounds are coming from the main pump, not the valve blocks or anything. Oh and of course i did do the chain test as you said. We started it up and it actually drove onto the trailer and into the backyard but it was tough. Fought itself really hard. had to do like a 20 point turn to turn 90 degrees. Feels super lousy but i dont know if its just the steering linkages.

 

[Hotrod1830]

Ok, so I finally picked it up and its in the backyard. After a quick pressure wash with all the covers and arms still down(my excuse for dirt still being around ), I took the cover off the steering linkage as it felt way too sloppy. I noticed that the centering spring was hanging loose. The levers are very sloppy and so that all needs rebuilt and adjusted I think. Next, I jacked it up with an axle stand on each axle as well as pulling the wheels and the side cover for the drive motor off. I started it up and played around with it for a bit. Up on jackstands i cant really tell a difference. The wheels went forward and back in either direction. But in different positions it would make really bad sounds, and pulling back hard on the right side felt like it was fighting itself. Whether "driving" or finding neutral and trying to hold the floppy handles there it would make squealing sounds at a minimum. I stuck my head in there and it sure sounds like it coming from the pump. The right side, red warning light is on which indicates...low charge pressure? So any tests i should do or just yank this motor out and tear it apart to look for some blown seals or something? I am quite confident all the sounds are coming from the main pump, not the valve blocks or anything. Oh and of course i did do the chain test as you said. We started it up and it actually drove onto the trailer and into the backyard but it was tough. Fought itself really hard. had to do like a 20 point turn to turn 90 degrees. Feels super lousy but i dont know if its just the steering linkages.

Almost sounds like you have a drive pump going out. More specificly a rotating group failure. I wouldnt run it anymore until you take the pumps out and check them out.

 

[Lowe.Buuck]

Ok, so I finally picked it up and its in the backyard. After a quick pressure wash with all the covers and arms still down(my excuse for dirt still being around ), I took the cover off the steering linkage as it felt way too sloppy. I noticed that the centering spring was hanging loose. The levers are very sloppy and so that all needs rebuilt and adjusted I think. Next, I jacked it up with an axle stand on each axle as well as pulling the wheels and the side cover for the drive motor off. I started it up and played around with it for a bit. Up on jackstands i cant really tell a difference. The wheels went forward and back in either direction. But in different positions it would make really bad sounds, and pulling back hard on the right side felt like it was fighting itself. Whether "driving" or finding neutral and trying to hold the floppy handles there it would make squealing sounds at a minimum. I stuck my head in there and it sure sounds like it coming from the pump. The right side, red warning light is on which indicates...low charge pressure? So any tests i should do or just yank this motor out and tear it apart to look for some blown seals or something? I am quite confident all the sounds are coming from the main pump, not the valve blocks or anything. Oh and of course i did do the chain test as you said. We started it up and it actually drove onto the trailer and into the backyard but it was tough. Fought itself really hard. had to do like a 20 point turn to turn 90 degrees. Feels super lousy but i dont know if its just the steering linkages.

Before you start tearing it apart, there are a few things you should do/check.
1. Hydraulic oil - level and condition.
2. Hydraulic filter.
3. Check drive motor Case Drain Filters. (See if there is metal shavings in them.)
4. Adjust steering linkage. Willie over on Heavy Equipment Forums did a nice write up. Repairing Creeping Bobcat
5. If Tazza jumps in, he should be able to tell you how to test charge pressure. He rebuilt the pump and motors in his 763.

 

[gatorguy]

Before you start tearing it apart, there are a few things you should do/check.
1. Hydraulic oil - level and condition.
2. Hydraulic filter.
3. Check drive motor Case Drain Filters. (See if there is metal shavings in them.)
4. Adjust steering linkage. Willie over on Heavy Equipment Forums did a nice write up. Repairing Creeping Bobcat
5. If Tazza jumps in, he should be able to tell you how to test charge pressure. He rebuilt the pump and motors in his 763.

Ok, I uploaded a video that is "private" so you can see it through the link to get an idea. https://youtu.be/p33W-EMnYVc Its too bad I didnt take another one later. I had the 743 running, cab and arms tilted up so I could specifically put my ear up to the pumps. As you can hear, as soon as I revved it up a bit. Sounds other than squealing occured ????. So I wasnt hearing any noises from the drive motors, but I will check. Case drain filters as in on the bottom of the chain case I take it somewhere. I'll dig around the manuals and see. I did check the hydraulic fluid...it is up past the minimum drain. Looks black but that's just from looking down in the tank. Also, Lowe.Buck, "Rubber over the tire tracks"???? are you meaning different sized tires? ...it has different sized tires front and back???? One of the rear loses air and the fronts are bald though so maybe this calls for new rubber. Added pics to the album https://drive.google.com/folderview?id=1QC0yuyZlSdvfzGpMY32zrUmpXFk0p-zB Thanks guys, Merry Christmas! Probably wont get to wrenching till boxing day.

 

[bobbie-g]

Ok, I uploaded a video that is "private" so you can see it through the link to get an idea. https://youtu.be/p33W-EMnYVc Its too bad I didnt take another one later. I had the 743 running, cab and arms tilted up so I could specifically put my ear up to the pumps. As you can hear, as soon as I revved it up a bit. Sounds other than squealing occured ????. So I wasnt hearing any noises from the drive motors, but I will check. Case drain filters as in on the bottom of the chain case I take it somewhere. I'll dig around the manuals and see. I did check the hydraulic fluid...it is up past the minimum drain. Looks black but that's just from looking down in the tank. Also, Lowe.Buck, "Rubber over the tire tracks"???? are you meaning different sized tires? ...it has different sized tires front and back???? One of the rear loses air and the fronts are bald though so maybe this calls for new rubber. Added pics to the album https://drive.google.com/folderview?id=1QC0yuyZlSdvfzGpMY32zrUmpXFk0p-zB Thanks guys, Merry Christmas! Probably wont get to wrenching till boxing day.

Hey, that doesn't sound toooooo bad to me. I could hear the hydraulic pump sounding off when you hit the stops on the bobtach, I don't really know what that means.

The different size tires should be dealt with. On each side, there is a drive chain to each tire. As I understand it, the drive chains share a common shaft between the tires. So both tires on one side are locked together. If they're different diameters, they fight each other and put more wear on the chains and drive sprockets than you want. You could go on the cheap and just buy two new tires for one side, and use the best two (identical circumference) tires for the other side.

You'll have lotsa fun with that new Christmas toy! Where are you located? I have a nice seat you'll be wanting!

Bobbie-G

 

[Lowe.Buuck]

Ok, I uploaded a video that is "private" so you can see it through the link to get an idea. https://youtu.be/p33W-EMnYVc Its too bad I didnt take another one later. I had the 743 running, cab and arms tilted up so I could specifically put my ear up to the pumps. As you can hear, as soon as I revved it up a bit. Sounds other than squealing occured ????. So I wasnt hearing any noises from the drive motors, but I will check. Case drain filters as in on the bottom of the chain case I take it somewhere. I'll dig around the manuals and see. I did check the hydraulic fluid...it is up past the minimum drain. Looks black but that's just from looking down in the tank. Also, Lowe.Buck, "Rubber over the tire tracks"???? are you meaning different sized tires? ...it has different sized tires front and back???? One of the rear loses air and the fronts are bald though so maybe this calls for new rubber. Added pics to the album https://drive.google.com/folderview?id=1QC0yuyZlSdvfzGpMY32zrUmpXFk0p-zB Thanks guys, Merry Christmas! Probably wont get to wrenching till boxing day.

Rubber Over the Tire Tracks are a style of tracks that fit over the tires like a big rubber band. They are driven by the tires and are tight on the tires. The point I was trying to make was if you had the front tires off the ground and both front tires rotated freely, a previous owner may have removed the front drive chains. Your machine has all the chains installed since all 4 wheels are operating normally.
Like bobbie-g, I did not hear a horrible noise when you were operating the drive motors. Might just be the video.
After watching the video, the another thing you should look at is the linkage attached to the Right Stick (as you are sitting in the operators seat). It has two functions. Moving it front to back controls the drive wheels. Moving it Left to Right controls the auxiliary hydraulics (those two hydraulic couplers on the left boom arm).
Activating the Aux hydraulics without an attachment will pressurize the line. With nowhere for the oil to flow, it will open the pressure relief valve letting the oil flow back to the tank. When the pressure relief valve opens you will hear a squealing noise. You will also lose power and the machine will operate sluggishly.
Pushing the Right Stick all the way right will latch the Aux Hydraulics on. This would be used for attachments like mowers or snow blowers where you are spinning a hydraulic motor.
Make sure that Right Lever is in the Neutral Position and that the linkages are moving freely.

 

[Lowe.Buuck]

Rubber Over the Tire Tracks are a style of tracks that fit over the tires like a big rubber band. They are driven by the tires and are tight on the tires. The point I was trying to make was if you had the front tires off the ground and both front tires rotated freely, a previous owner may have removed the front drive chains. Your machine has all the chains installed since all 4 wheels are operating normally.
Like bobbie-g, I did not hear a horrible noise when you were operating the drive motors. Might just be the video.
After watching the video, the another thing you should look at is the linkage attached to the Right Stick (as you are sitting in the operators seat). It has two functions. Moving it front to back controls the drive wheels. Moving it Left to Right controls the auxiliary hydraulics (those two hydraulic couplers on the left boom arm).
Activating the Aux hydraulics without an attachment will pressurize the line. With nowhere for the oil to flow, it will open the pressure relief valve letting the oil flow back to the tank. When the pressure relief valve opens you will hear a squealing noise. You will also lose power and the machine will operate sluggishly.
Pushing the Right Stick all the way right will latch the Aux Hydraulics on. This would be used for attachments like mowers or snow blowers where you are spinning a hydraulic motor.
Make sure that Right Lever is in the Neutral Position and that the linkages are moving freely.

The hydraulic motor Case Drains are the small hydraulic hoses on the drive motors. The two large hoses control the motor rotation. Some of the pressurized oil inside the motor will get past the normal clearances into the motor case. To prevent the seals from blowing out, that oil is routed to the motor case drain and out that small hose and routed back to the hydraulic tank.
If you follow those two small hoses, you should find one or two aluminum inline filters. They unscrew and there is a bronze filter inside the aluminum shell. These filters capture any metal shavings as this oil is routed back to the hydraulic tank.
Opening and checking the filters will tell you if a drive motor is starting to wear/fail.

 

[Tazza]

The hydraulic motor Case Drains are the small hydraulic hoses on the drive motors. The two large hoses control the motor rotation. Some of the pressurized oil inside the motor will get past the normal clearances into the motor case. To prevent the seals from blowing out, that oil is routed to the motor case drain and out that small hose and routed back to the hydraulic tank.
If you follow those two small hoses, you should find one or two aluminum inline filters. They unscrew and there is a bronze filter inside the aluminum shell. These filters capture any metal shavings as this oil is routed back to the hydraulic tank.
Opening and checking the filters will tell you if a drive motor is starting to wear/fail.

Sorry, I'm late to the party on this one, she is one of the first models of 743. See the square block on the hydraulic pump, left side there are 3 hoses going into the block, remove the middle hose and fitting, there is a bronze screen behind it. It's almost always missed and causes drive issues.
The motor blow-by could be wear, generally if it's really bad, people just swap it for a V2203 out of a refrigeration unit.

 

[gatorguy]

Sorry, I'm late to the party on this one, she is one of the first models of 743. See the square block on the hydraulic pump, left side there are 3 hoses going into the block, remove the middle hose and fitting, there is a bronze screen behind it. It's almost always missed and causes drive issues.
The motor blow-by could be wear, generally if it's really bad, people just swap it for a V2203 out of a refrigeration unit.

Bobbie G - Haha, yes the seat could use being replaced. I'm in Lowermainland, BC. So finally got that 1 1/2" fitting off the block and pulled the micron filter. It was dirty, some metal shavings. I tried cleaning off with compressed air and brake clean but I see its starting to crack so will probably just replace it. I put everything back together without the filter/aluminum housing/spring. I checked for case drain filters...followed both lines to the relief pressure valve but no inline filters...I think I read that those were only on later model ones? I ran it...although it was low on hydraulic oil so didnt go crazy. I wonder if alot of the sound from the pump isnt as bad. But maybe it is the drive motor. Check out the right side when going back and that noise it makes...also on both sides it appears it goes faster in reverse than forwards....I guess. I pulled the hydraulic oil filter off and only it was stuck on there. Crumpled the filter before it would loosen up. Took it apart and there were some very fine metal shavings but nothing crazy. I guess I should throw new oil in and filter to see what happens? https://youtu.be/WGqLsDh57Q4 there are some more sounds. I would say it is quite as bad as before. But then ahhaom, it wasnt revved up near as much. At about 48 sec I engaged the aux hydraulics as you can hear. And yes...had a little spill????

 

[gatorguy]

Bobbie G - Haha, yes the seat could use being replaced. I'm in Lowermainland, BC. So finally got that 1 1/2" fitting off the block and pulled the micron filter. It was dirty, some metal shavings. I tried cleaning off with compressed air and brake clean but I see its starting to crack so will probably just replace it. I put everything back together without the filter/aluminum housing/spring. I checked for case drain filters...followed both lines to the relief pressure valve but no inline filters...I think I read that those were only on later model ones? I ran it...although it was low on hydraulic oil so didnt go crazy. I wonder if alot of the sound from the pump isnt as bad. But maybe it is the drive motor. Check out the right side when going back and that noise it makes...also on both sides it appears it goes faster in reverse than forwards....I guess. I pulled the hydraulic oil filter off and only it was stuck on there. Crumpled the filter before it would loosen up. Took it apart and there were some very fine metal shavings but nothing crazy. I guess I should throw new oil in and filter to see what happens? https://youtu.be/WGqLsDh57Q4 there are some more sounds. I would say it is quite as bad as before. But then ahhaom, it wasnt revved up near as much. At about 48 sec I engaged the aux hydraulics as you can hear. And yes...had a little spill????

^^ That was sopposed to have a empty line between my reply to bobbie - g, and the reply to the rest of you. So finally got that... But anyway, I will also mention that I tried loosening that small (9/16?) mounting bolt off the port block and it appears it was stripped...i dont know if that it just a mounting bolt, or if that has a crucial function in the system but just throwing that out there.

 

[gatorguy]

^^ That was sopposed to have a empty line between my reply to bobbie - g, and the reply to the rest of you. So finally got that... But anyway, I will also mention that I tried loosening that small (9/16?) mounting bolt off the port block and it appears it was stripped...i dont know if that it just a mounting bolt, or if that has a crucial function in the system but just throwing that out there.

Update, so I've got a 40 micron filter coming tomorrow. I ran it with some new fluid in the reservoir and maybe some difference. I popped the front cover off the chaincase and this is what I found... (Pics added https://drive.google.com/folderview?id=1QC0yuyZlSdvfzGpMY32zrUmpXFk0p-zB ) So milky oil, and very low. I measure it at 3" off the bottom. From reading up on the forum it appears it was sopposed to come up to trh bottom of the fill neck?! Some basic math with the chain case being 9"×48"×3" not accounting for space filled up by parts yields about 5-6 gallons out of the 9 that's sopposed to be in there. There is obviously no leakage in from up top. Sealed with alot of goop and the case is low...so my guess is its leaked out the axle seals? There is some junk by them, but not a ton. From reading up it looks like quite a job. I found 10w30oil at $2.80 a liter to fill it with anyway but I guess these axle seals will have to be looked into. I'll dump the hydraulic fluid in there I had drained out and do a test to see if it is seeping from the axle seals. Also, in the second picture you'll see the teeth look kinda sharper points which indicate wear? And also some damage to the case. But I dont see what that would be. I tried stretching the chain over there but couldnt so must be past damage. Is there a certain way to check these chains tension? What is spec? Couldnt find it in the manuals. But I'm guessing that this lack of lubrication could be causing alot of the noise I'm hearing. Stuck a pry bay up to my ear and went around the machine...seems very consistent with both sides. I'd also like to check the charge pressure. So I just need a 1000psi guage I take it and some fittings? Thanks all