743B need some advice

[sirbean]

I have a 743B that works great but am starting to have a weird problem and could use some advice. When the machine has set over night the left side will not drive till you shake handle back and forth a few times then it goes. Works fine the rest of the day. The following day it starts all over. I have no manual for the machine, but would love to find one. Any advice would be appreciated. There is no noise when it doesnt work and it is like that pump is not creating flow for a minute. I have crawled through this forums archives looking for some thing like this and I didn't see anything. Thank you all for any help.

 

[Tazza]

Do you have any oil leaks at all?
Have you changed the oil filter too?
Things like that to me sound like your charge pressure is taking a little while to build up. A plugged filter can be a cause of this.

 

[sirbean]

Do you have any oil leaks at all?
Have you changed the oil filter too?
Things like that to me sound like your charge pressure is taking a little while to build up. A plugged filter can be a cause of this.

new oil and new filters last fall...about 100 hours. There is a small leak at shaft going into pump that control direction. Where do you check charge pressure and what should it be? Anyone have a schematic of the hydraulics for my skidsteer? Thanks

 

[Tazza]

new oil and new filters last fall...about 100 hours. There is a small leak at shaft going into pump that control direction. Where do you check charge pressure and what should it be? Anyone have a schematic of the hydraulics for my skidsteer? Thanks

There should be a charge pressure sender that you can remove and install a manual gauge. It is generally at the pump or port block near the pump. Hopefully someone with an 843 will be able to tell you for sure.

 

[Tazza]

There should be a charge pressure sender that you can remove and install a manual gauge. It is generally at the pump or port block near the pump. Hopefully someone with an 843 will be able to tell you for sure.

I got mixed up, 743B should be like the 743. There is an elboe on the top of the pump with a round sender with 2 wires hanging off it, this is where you install a gauge.

 

[sirbean]

I got mixed up, 743B should be like the 743. There is an elboe on the top of the pump with a round sender with 2 wires hanging off it, this is where you install a gauge.

what should be the pressure at sending unit? Does this hydrostat pump get its charge pressure from the small gear pump that runs the cyclinders or does it have its own charge pump? Thanks

 

[sirbean]

what should be the pressure at sending unit? Does this hydrostat pump get its charge pressure from the small gear pump that runs the cyclinders or does it have its own charge pump? Thanks

I worked on it this morning. I have the steering linkages disconnected from the pump. The wheels are off the ground on jack stands. I started it and moved the pump arm individually . The pump towards the front of the machine which runs the right side works great. the rear pump which runs the left side just barely moves the wheels. Move it back and forth. No real improvement . I ran them at same time and the back pump took off. Now it works fine till it sets. It seems it in the pump to me because both hydrastat pumps rely on the same charge pressure source. If was a charge pressure problem wouldn't both the pump not work. I don't think there is anything in the motors that would cause this... Any advice or thoughts. Thanks

 

[sirbean]

I worked on it this morning. I have the steering linkages disconnected from the pump. The wheels are off the ground on jack stands. I started it and moved the pump arm individually . The pump towards the front of the machine which runs the right side works great. the rear pump which runs the left side just barely moves the wheels. Move it back and forth. No real improvement . I ran them at same time and the back pump took off. Now it works fine till it sets. It seems it in the pump to me because both hydrastat pumps rely on the same charge pressure source. If was a charge pressure problem wouldn't both the pump not work. I don't think there is anything in the motors that would cause this... Any advice or thoughts. Thanks

also. With skidsteer on jack stands, the left side wheels will spin but the right side wont. the engine is off. the side that spins is the side that acts up

 

[Tazza]

also. With skidsteer on jack stands, the left side wheels will spin but the right side wont. the engine is off. the side that spins is the side that acts up

The charge pressure should be 90-120 psi from memory.
Now, you have a wheel that will turn with the engine off, it shouldn't do this. Seals inside the drive motor could be the cause. It may be allowing oil to flow through the motor when it shouldn't be.
One way to know for sure is to swap the motors over. The problem is, you need to swap fittings too, it's not a quick job, but it will tell you if the problem is in the motor or pump.

 

[Ken743B]

also. With skidsteer on jack stands, the left side wheels will spin but the right side wont. the engine is off. the side that spins is the side that acts up

Here is what could be the possible cause(s). The steering linkage needs adjustment. The high pressure replenishing valve(s) are damaged. The shuttle valve in the hydrostatic motor is not working correctly. The valve plate seals in the hydrostatic motor are damaged. The hydrostatic pumps have damage. The final drive chain is broken. The hydrostatic motor has damage.

 

[sirbean]

Here is what could be the possible cause(s). The steering linkage needs adjustment. The high pressure replenishing valve(s) are damaged. The shuttle valve in the hydrostatic motor is not working correctly. The valve plate seals in the hydrostatic motor are damaged. The hydrostatic pumps have damage. The final drive chain is broken. The hydrostatic motor has damage.

Thank you all for the tips and advice. Ill get to work and be sure to tell you what I find! Thanks again!!!