Power steering problem after hydraulic pump rebuild.

JR_cattleco

New member

Equipment
Kubota M4030, M6800, M8200, M9000
Aug 2, 2021
4
0
1
North MS
I have a M4030SU, that had a leak in the hydraulic pump. It was a blown gasket and i replaced it.
After reinstalling the pump all of the hydraulics worked except the steering.
If i use the loader to raise the front off the ground the steering work fine. Only with the weight of the tractor does it stop working. I have very little restriction on the steering when i turn the steering-wheel.
I tried to bleed it at the power steering cylinder, and i get a lot of air out of it.

If i bleed at the pump i get no air, just fluid.
Any ideas on why i'm getting air into the system?
 

Dave_eng

Well-known member
Lifetime Member

Equipment
M7040, Nuffield 465
Oct 6, 2012
4,204
446
83
Williamstown Ontario Canada
I have a M4030SU, that had a leak in the hydraulic pump. It was a blown gasket and i replaced it.
After reinstalling the pump all of the hydraulics worked except the steering.
If i use the loader to raise the front off the ground the steering work fine. Only with the weight of the tractor does it stop working. I have very little restriction on the steering when i turn the steering-wheel.
I tried to bleed it at the power steering cylinder, and i get a lot of air out of it.

If i bleed at the pump i get no air, just fluid.
Any ideas on why i'm getting air into the system?
Typical symptoms of a hose in the wrong place.

Unfortunately I cannot find a WSM to be more specific.

Do you have any manuals with hydraulic schematic?

Dave
 

eserv

Well-known member

Equipment
BX24, A1000 Kubota Generator
May 27, 2009
2,101
85
48
Hardisty, Alberta
I have a M4030SU, that had a leak in the hydraulic pump. It was a blown gasket and i replaced it.
After reinstalling the pump all of the hydraulics worked except the steering.
If i use the loader to raise the front off the ground the steering work fine. Only with the weight of the tractor does it stop working. I have very little restriction on the steering when i turn the steering-wheel.
I tried to bleed it at the power steering cylinder, and i get a lot of air out of it.

If i bleed at the pump i get no air, just fluid.
Any ideas on why i'm getting air into the system?
Did you remember to install the little coupler between the two hydraulic pumps?
 

JR_cattleco

New member

Equipment
Kubota M4030, M6800, M8200, M9000
Aug 2, 2021
4
0
1
North MS
Typical symptoms of a hose in the wrong place.

Unfortunately I cannot find a WSM to be more specific.

Do you have any manuals with hydraulic schematic?

Dave
I only had to re-attach the outlets and 1 inlet. I don't think they would reach the wrong ports. I didn't remove anything else so I'm pretty sure the connections are correct.
I don't have a complete drawing of the hydraulic system, only the on line parts details, that only show one section at time.
 

JR_cattleco

New member

Equipment
Kubota M4030, M6800, M8200, M9000
Aug 2, 2021
4
0
1
North MS
Did you remember to install the little coupler between the two hydraulic pumps?
I'm pretty sure I did. I didn't have any left over parts. Maybe I should take it back apart and check.
I thought since the loader and the three point hitch were working I had must have it back together correctly.
Plus if I loosen any of the the 3 outlets, each will really pump out the hydraulic fluid.
 

eserv

Well-known member

Equipment
BX24, A1000 Kubota Generator
May 27, 2009
2,101
85
48
Hardisty, Alberta
I'm pretty sure I did. I didn't have any left over parts. Maybe I should take it back apart and check.
I thought since the loader and the three point hitch were working I had must have it back together correctly.
Plus if I loosen any of the the 3 outlets, each will really pump out the hydraulic fluid.
I never actually had the joy of working on a M5030su so that's all i got!
 

Dave_eng

Well-known member
Lifetime Member

Equipment
M7040, Nuffield 465
Oct 6, 2012
4,204
446
83
Williamstown Ontario Canada
The power steering uses its own pump and the 3 pt pump provides no pressurized oil to the steering.

The steering control valve has a portion of the valve called a Gerotor which stands for "generated rotor"

The Gerotor directs the oil flow when the engine is running so you can steer left or right.

When the engine is stopped, the Gerotor acts as a small pump and gives you steering control so for example if the engine were to stall at the top of a long hill, you could still steer the tractor but with increased effort.

Try to steer with the engine stopped. I am interested to know if you can get movement out of the front wheels.

Dave
 

JR_cattleco

New member

Equipment
Kubota M4030, M6800, M8200, M9000
Aug 2, 2021
4
0
1
North MS
I figured it out. The M4030SU, has its own hydraulic tank for the power steering. It is completely separate from the hydraulic system.
I removed the inlet and ran it and put my finger over the inlet port and there was a lot of suction so i determined that it was getting starved for fluid. I traced the lines on the inlet port back to a small tank on top of the engine. After cleaning it up i discovered a dip stick on it checked it and it was empty. Added Hydraulic fluid to this tank and presto changeo the steering started working. Evidently when i took this port off the pump the fluid ran out of the tank.
Thanks for all the good information hopefully this will save someone out there a lot of time and pain.
I must have rebuilt the pump 16 times trying to find the problem.