743 giving me problems

[zlconstruction]

My bobcat 743 is acting very strange. When i first start it up and use it for about 10 min it runs fine and everythings works perfect, but after the 10 min it seams to be lossing lots of its power. I can hardly steer the 743 when it is on a hard surface and when i try to steer it it sounds like the hydraulic motor is growling really lound. It is especially feels like the left side is alot weeker then the right. Also when i try to lift the arms up with a load of dirt and drive forward the arms go up extramly slow or not up at all unless i stop moving and let all the hydraulic power go to the arms. I had the bobcat dealership look at my 743 and the said it was the left drive motor that was bad. Well i went out and bought a new motor and what do you know there is no difference. It is still just as bad. The only thing i can think of that can be wrong is something with the hydraulic pump. Has anyone else had this problem? I have changed the hydraulic fluid and filter. I am stumped i cant figure it out.

 

[Tazza]

I just posted a similar response to something that would cause the same problem.
When the cab is in the air, what do you see on the hydraulic pump (the one rite at the front)? do you see a square block sitting on top with 5 hoses connected or is there a large hose that runs to a block near the throttle lever?
If it was just the motor, it would have a hard time steering one way, not both ways.
What oil are you running?
Check the oil cooler too.
The early 743's had a hidden oil filter that causes havoc. Just like your problem, it runs fine till it warms and squeals like a stuck pig when trying to turn. Has a massive lack of power. BUT this doesn't cause any problems to your hydraulics.
Wither way, let me know if it has the square block and if so, i will tell you where the filter is and how to get it.

 

[zlconstruction]

I just posted a similar response to something that would cause the same problem.
When the cab is in the air, what do you see on the hydraulic pump (the one rite at the front)? do you see a square block sitting on top with 5 hoses connected or is there a large hose that runs to a block near the throttle lever?
If it was just the motor, it would have a hard time steering one way, not both ways.
What oil are you running?
Check the oil cooler too.
The early 743's had a hidden oil filter that causes havoc. Just like your problem, it runs fine till it warms and squeals like a stuck pig when trying to turn. Has a massive lack of power. BUT this doesn't cause any problems to your hydraulics.
Wither way, let me know if it has the square block and if so, i will tell you where the filter is and how to get it.

I lifted up the cab and took a look at the hydraulic pump and it turns out that there is a large hose that runs to a block near the throttle lever. I am running 10w30 in the system now. And i have not had a chance to look at the oil cooler yet.

 

[Tazza]

I lifted up the cab and took a look at the hydraulic pump and it turns out that there is a large hose that runs to a block near the throttle lever. I am running 10w30 in the system now. And i have not had a chance to look at the oil cooler yet.

Ok, you have the newer style setup.
The oil you are using is correct, all i can think of is you have blocked fins on the cooler causing excessive heat. The block thats on the other end of that large hose has a temperature sender in it so if the temperature is too high, a light should light up (if the sender is working and connected up).

 

[zlconstruction]

Ok, you have the newer style setup.
The oil you are using is correct, all i can think of is you have blocked fins on the cooler causing excessive heat. The block thats on the other end of that large hose has a temperature sender in it so if the temperature is too high, a light should light up (if the sender is working and connected up).

ha O so thats what that little red light is. Ya it turns on after about ten min of using the 743. I took everything apart to get to the oil cooler and it was preatty dirty. I am going to finish cleaning it tomaro and i will put it all back and see if works better. Thanks for the tip hopefully it will work. Wish me luck!

 

[Tazza]

ha O so thats what that little red light is. Ya it turns on after about ten min of using the 743. I took everything apart to get to the oil cooler and it was preatty dirty. I am going to finish cleaning it tomaro and i will put it all back and see if works better. Thanks for the tip hopefully it will work. Wish me luck!

The best tip i can give you is to remove the covers, get de-greaser or diesel in a spray bottle and soak the oil cooler from the top through the radiator (good to give it a clean too) and from the inspection covers. Give it several soakings and wash it down with a high pressure washer. You may have to give it a few goes, but its needed!. If the oil runs too hot for too long something will give. I have seen the rotating group from a 843 that had 1 or 2 holes worn out really bad because it was over heated. A new rotating group is only a few K!!!!
*crosses fingers*

 

[zlconstruction]

The best tip i can give you is to remove the covers, get de-greaser or diesel in a spray bottle and soak the oil cooler from the top through the radiator (good to give it a clean too) and from the inspection covers. Give it several soakings and wash it down with a high pressure washer. You may have to give it a few goes, but its needed!. If the oil runs too hot for too long something will give. I have seen the rotating group from a 843 that had 1 or 2 holes worn out really bad because it was over heated. A new rotating group is only a few K!!!!
*crosses fingers*

I cleaned the oil cooler with de-greaser preatty good and spreyed it down with water. It was mostly dust and bits of crap stuck in the fins. The radiator was preatty dirty too. I did the same with that too. I put it all back and ran the 743 and the same thing agine. This time i payed more attention to what was going on. After about 8 min ( its hot out side today) of working it started to really make that load noise. Another thing i noticed is when you first start driving it makes that noise at low rpm but if you turn it up it goes away kind of. Its so loud it even drowns out the sound of the motor and 1/2 throtel. I try to turn right 180 degrees and it makes the sound but when you turn left wow is it loud and i almost have to pull the stick all the way back and it still hardly does not want turn. And when i look at the left hand side wheels they are hardly turning they just kind of skid along unlike the right wich skids and turns fine. I also feel the left hand stick kind of vibrate more while i try to turn and its harder to pull on. Another thing i obseerved was that it does not drive straight. The left lags. I hope there is a solution, i am sure there is and all it will is take time to find

 

[Tazza]

I cleaned the oil cooler with de-greaser preatty good and spreyed it down with water. It was mostly dust and bits of crap stuck in the fins. The radiator was preatty dirty too. I did the same with that too. I put it all back and ran the 743 and the same thing agine. This time i payed more attention to what was going on. After about 8 min ( its hot out side today) of working it started to really make that load noise. Another thing i noticed is when you first start driving it makes that noise at low rpm but if you turn it up it goes away kind of. Its so loud it even drowns out the sound of the motor and 1/2 throtel. I try to turn right 180 degrees and it makes the sound but when you turn left wow is it loud and i almost have to pull the stick all the way back and it still hardly does not want turn. And when i look at the left hand side wheels they are hardly turning they just kind of skid along unlike the right wich skids and turns fine. I also feel the left hand stick kind of vibrate more while i try to turn and its harder to pull on. Another thing i obseerved was that it does not drive straight. The left lags. I hope there is a solution, i am sure there is and all it will is take time to find

Its normal for it to make a lot of growling at low rpm, you will feel a lot of vibration in the sticks too. At mid to full throttle it should be smooth and little noise should be heard from the hydrostatics unless you push in to a pile of dirt.
One last thing i would try before attacking the pump would be to swap the hydro motors over. If the problem goes from one side to the other it soulds like a motor problem. If not, it could be the pump(s). Your hydraulics still operate normally? like lift and tilt, no noise while siting still? It will growl a bit if the RPM is low, thats normal. But at a good speed it should be quiet and quite responsive.
You may have to take it to the dealer to get a test done on the pumps. They can do a flow and pressure test that will tell you if the pumps are ok or not. Not something you wanted to hear i'm sure, but it may be needed yet.
You did mention you bought a new motor for the LHS so it does sound like a pump problem. The problem is your main hydraulic pump acts as a charge pump for the 2 pumps for the left and right side drive. If its weak, there may not be enough charge pressure for the other pumps that will cause a loss of drive. You could put a pressure gauge on the pump, rite at the back near the fuel tank. There is a pressure switch here, remove it and put a gauge in. The pressure from memory should be around 100PSI. My manual will give me an exact number. Block the loader and start it with the gauge attached. Try moving the sticks and see what the pressure reads. There shouldn't be buch of a drop as its not under any load. I will try and get time to do this to mine to compair pressure readings.
If i don't get back to you tonight, you can e-mail me. My address is in my profile, this way i can't forget to do it!

 

[zlconstruction]

Its normal for it to make a lot of growling at low rpm, you will feel a lot of vibration in the sticks too. At mid to full throttle it should be smooth and little noise should be heard from the hydrostatics unless you push in to a pile of dirt.
One last thing i would try before attacking the pump would be to swap the hydro motors over. If the problem goes from one side to the other it soulds like a motor problem. If not, it could be the pump(s). Your hydraulics still operate normally? like lift and tilt, no noise while siting still? It will growl a bit if the RPM is low, thats normal. But at a good speed it should be quiet and quite responsive.
You may have to take it to the dealer to get a test done on the pumps. They can do a flow and pressure test that will tell you if the pumps are ok or not. Not something you wanted to hear i'm sure, but it may be needed yet.
You did mention you bought a new motor for the LHS so it does sound like a pump problem. The problem is your main hydraulic pump acts as a charge pump for the 2 pumps for the left and right side drive. If its weak, there may not be enough charge pressure for the other pumps that will cause a loss of drive. You could put a pressure gauge on the pump, rite at the back near the fuel tank. There is a pressure switch here, remove it and put a gauge in. The pressure from memory should be around 100PSI. My manual will give me an exact number. Block the loader and start it with the gauge attached. Try moving the sticks and see what the pressure reads. There shouldn't be buch of a drop as its not under any load. I will try and get time to do this to mine to compair pressure readings.
If i don't get back to you tonight, you can e-mail me. My address is in my profile, this way i can't forget to do it!

Ya i was hoping it wouldn't be with the hydraulic pumps but it sounds like thats what the problem may be. What type of pressure gauge should i use to test this pump. Where can i get one. I would like to see if i can avoid the dealer they were the ones that told me a needed a LHS Drive motor. They even came out twice to my house to look at the 743 and told me for sure that the drive motor was the problem boy were the wrong. They even told me to get rid of the thing and they have a great finance deal going now on a brand new bobcat. I dont use the bobcat enough to go out and spend 20-30k on a new one. I would like to fix it up and restore it to good working condition. Its more of a hoby/project for me rather than a thing i use everyday. If it is the pump is it hard to replace and will it cost alot of money? Let me know. Thanks for the help.

 

[sterlclan]

Ya i was hoping it wouldn't be with the hydraulic pumps but it sounds like thats what the problem may be. What type of pressure gauge should i use to test this pump. Where can i get one. I would like to see if i can avoid the dealer they were the ones that told me a needed a LHS Drive motor. They even came out twice to my house to look at the 743 and told me for sure that the drive motor was the problem boy were the wrong. They even told me to get rid of the thing and they have a great finance deal going now on a brand new bobcat. I dont use the bobcat enough to go out and spend 20-30k on a new one. I would like to fix it up and restore it to good working condition. Its more of a hoby/project for me rather than a thing i use everyday. If it is the pump is it hard to replace and will it cost alot of money? Let me know. Thanks for the help.

napa sells hydraulic gauges in different pressures I just got a 4000 pound one for 25 dollars if all you are testing is charge pressure get a 1000 to 2000 pound gauge as the 4000 pound one starts at about 300 pounds I used a 200 pound oil pressure gauge to test mine and tazza is correct it runs about 100 to 125 good luck......... Jeff................ ps this guy sells pumps and pump parts http://stores.ebay.com/skidloader-hydraulic-parts-source_Bobcat-Parts_W0QQcolZ4QQdirZ1QQfsubZ9685124QQftidZ2QQtZkm

 

[Tazza]

napa sells hydraulic gauges in different pressures I just got a 4000 pound one for 25 dollars if all you are testing is charge pressure get a 1000 to 2000 pound gauge as the 4000 pound one starts at about 300 pounds I used a 200 pound oil pressure gauge to test mine and tazza is correct it runs about 100 to 125 good luck......... Jeff................ ps this guy sells pumps and pump parts http://stores.ebay.com/skidloader-hydraulic-parts-source_Bobcat-Parts_W0QQcolZ4QQdirZ1QQfsubZ9685124QQftidZ2QQtZkm

From memory the pump is a TA1919. Its made by Vickers/Eaton.
Have a look at: http://www.dbzdiesel.com/vickers.html
I have never used these people but a quick Google search found them. The main parts of the pump are the rotating group and wafer plates (or swash plate) that you can see in the picture. You can always call around to see what price you can get on a new set to fully re-co the pump. Unfortunatly they are not cheap. Still cheaper than buying a new one or parts off Bobcat.
They aren't hard to replace, but you MUST take note of directions of spacers on the shaft where bearings sit. If you go this way, i can give you a PDF that shows what to do.
*if* you go this far, you may want to work on the right hand drive motor too, then you have done a complete job, but this is up to you.
Before you go pulling the pump down, you may want to get a test done just to be sure.
Do let me know how you go.
One last thing, remove the pressure switch and install a small valve with clear tubing and run it back to your oil tank. There should be no bubbles when the machine is running. If there are, you are geting cavetation. This could be from low charge pressure, but i'm not exactly sure where this is regulated.

 

[zlconstruction]

From memory the pump is a TA1919. Its made by Vickers/Eaton.
Have a look at: http://www.dbzdiesel.com/vickers.html
I have never used these people but a quick Google search found them. The main parts of the pump are the rotating group and wafer plates (or swash plate) that you can see in the picture. You can always call around to see what price you can get on a new set to fully re-co the pump. Unfortunatly they are not cheap. Still cheaper than buying a new one or parts off Bobcat.
They aren't hard to replace, but you MUST take note of directions of spacers on the shaft where bearings sit. If you go this way, i can give you a PDF that shows what to do.
*if* you go this far, you may want to work on the right hand drive motor too, then you have done a complete job, but this is up to you.
Before you go pulling the pump down, you may want to get a test done just to be sure.
Do let me know how you go.
One last thing, remove the pressure switch and install a small valve with clear tubing and run it back to your oil tank. There should be no bubbles when the machine is running. If there are, you are geting cavetation. This could be from low charge pressure, but i'm not exactly sure where this is regulated.

First off thanks for the help and the advice. I am going to go buy myself some hydraulic test gauges today and i am going to test the charge pressure. So if i do have a low charge pressure that means that the charge pump is bad? I will let you know ho it goes.

 

[Tazza]

First off thanks for the help and the advice. I am going to go buy myself some hydraulic test gauges today and i am going to test the charge pressure. So if i do have a low charge pressure that means that the charge pump is bad? I will let you know ho it goes.

The main hydraulic pump acts as the charge pump as well as the hydraulic pump.
Start with checking the charge pressure and work from there.

 

[zlconstruction]

The main hydraulic pump acts as the charge pump as well as the hydraulic pump.
Start with checking the charge pressure and work from there.

it has been a while since i was on i finally got a chance to take a look at the charge pressure on the main hydraulic pump. I hooked up a gage and the pressure read 100 psi at almost full throttle and 90 psi at idol. So i think that is fine for the pressure so it must be the pump for the left hand side. Is there a way to test that. Or can it be something else ?

 

[Tazza]

it has been a while since i was on i finally got a chance to take a look at the charge pressure on the main hydraulic pump. I hooked up a gage and the pressure read 100 psi at almost full throttle and 90 psi at idol. So i think that is fine for the pressure so it must be the pump for the left hand side. Is there a way to test that. Or can it be something else ?

The only test you can do is to move the motor from the left to the right. If the problem moves its the motor, if it doesn't it seems it may indeed be the pump.

 

[sterlclan]

The only test you can do is to move the motor from the left to the right. If the problem moves its the motor, if it doesn't it seems it may indeed be the pump.

its probably easier to switch hoses at the pump just remember the levers will be switched side to side and backwards but you can tell if it is a pump then....Jeff

 

[Tazza]

its probably easier to switch hoses at the pump just remember the levers will be switched side to side and backwards but you can tell if it is a pump then....Jeff

If its the same setup as mine, moving hoses at the pump is not possible. 2 of the hoses are crimped to metal tube lines that go behind the pump near the engine and down to the motors. I'm not sure what they used on earlier machines, mine is a 90 model. My old 78 model 731 did not have metal lines and changing hoses at the pump was possible.
Which ever way you feel is easiest go that way. If the problem switches sides it will be that hydro pump section. Remember you can buy kits to repair pump sections.

 

[zlconstruction]

If its the same setup as mine, moving hoses at the pump is not possible. 2 of the hoses are crimped to metal tube lines that go behind the pump near the engine and down to the motors. I'm not sure what they used on earlier machines, mine is a 90 model. My old 78 model 731 did not have metal lines and changing hoses at the pump was possible.
Which ever way you feel is easiest go that way. If the problem switches sides it will be that hydro pump section. Remember you can buy kits to repair pump sections.

well i am sure that it is the pump that is bad because i bought a new drive motor for the left hand side and the problem is still there. Or do you think i should still switch it out with the right hand side drive motor? If it is the pump that is bad i am sure it wont be too difficult to change out that hydro pump section. I went on to ebay and found a guy that was selling these rebuilt pump sections and they looked to be resonable. I know the big blue pump is divided into three sections and would be changing out one section to correct my problem with the left hand drive. Also which section of the pump is it?

 

[Tazza]

well i am sure that it is the pump that is bad because i bought a new drive motor for the left hand side and the problem is still there. Or do you think i should still switch it out with the right hand side drive motor? If it is the pump that is bad i am sure it wont be too difficult to change out that hydro pump section. I went on to ebay and found a guy that was selling these rebuilt pump sections and they looked to be resonable. I know the big blue pump is divided into three sections and would be changing out one section to correct my problem with the left hand drive. Also which section of the pump is it?

If you have a new drive motor it has to be the pump or the relief valve.
The last thing you can try is the relief valves in the block between the 2 pump sections. The rear pump is for the left and the front is for the right if memory serves. Try removing the plugs and see if there is any crap stick in the valves. Check the springs too, it may have broken. If everything looks ok it will probably be the pump. Remember, the front pump is the hydraulic pump/charge pump. the next two are the hydrostatic pumps, they are back to back with a section between where the hoses connect. These are 2 separate pumps.
Can you give me the details of the pump you saw on e-bay? the only ones i have seen are the hydraulic pump complete or the *kit* to fix the hydro pump. I haven't seen parts for the hydrostatic pump though.
Before you buy anything crack the pump open and have a look, just to be sure you don't buy parts that are not needed.