HAVING A PROBLEM WITH MY CAT 446 STEERING , IT IS VERY DIFFICULT TO STEER, I HAVE CHECKED THE SIGNAL VALVE , REBUILT THE STEERING CYLINDER, REPLACED THE METER VALVE,REPLACED THE PRESSURE RELIEF VALVE , INSPECTED ALL LINES FOR INTERNAL DAMAGE AND THE PROBLEM STILL WONT GO. THE METER IS A NEW CAT REPLACEMENT, CHECKED THE SIGNAL LINES FOR AIR, AND THERE IS NO PROBLEM WITH THE COLUM.. THIS ONE IS A BRAIN BUSTER AND I THINK I HAVE ALOT OF IT , IS THERE ANYONE OUT THERE WITH ANY SUGGESTIONS.:Banghead
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Cat 446
- Thread starter QUANIE
- Start date
Please switch off your caps lock
willie59
Administrator
Don't know for sure, but I assume the oil is supplied by the hyd pump for work equipment. Does the loader/hoe functions work ok? The machine may use a priority flow divider to supply oil to steering and loader/hoe functions. It meters oil to both functions so you can drive, steer, and lift bucket at the same time without one function interupting the other, not sure about this machine. Just a thought. 
hammerdwn20
Well-Known Member
maybe something in the front end is binding? id unhook the steering cylinder and move the wheels left and right by hand.
willie59
Administrator
I just don't know enough about this machines hyd components to be much help. Is this something that one day happened, or has it been like this all along?
hdfatboynh
New Member
I have a cat 426 which has the same type of problem, steers better when the motor is reved up but the hoe and bucket work slow all the time. anyone have any suggestions for me i getting ready to dig into this issue might help to know where to start
willie59
Administrator
Well, I was thinkin'...if it's been that way since you've had it, could be hoses hooked up wrong. But if it happened suddenly, sounds like something went south. I just don't know this machines components. Does the machine use the same pump to deliver oil to steering as well as loader/hoe? If so, does the loader/hoe have good power? If it does, you at least know the problem isn't the pump. If you've replaced the orbital valve and rebuilt the cylinders, it still sounds like a problem with a priority flow divider, but I'm not certain with anything on this one.
I have opened and inspected the priority valve, it was one of the first things that i did, the only conclusion that I have come to is though the spool looks good , it must be sticking so i will replace it, because the bucket lift and tilt works fine.
dogboneshd
Well-Known Member
Keep us posted QUANIE.
As a possible suggestion, lift the machine up on the bucket and stabs, and with the engine OFF, try to steer the machine left and right. It will be hard, but there is a thing called a HMU in the column with a small gear pump in it for steering backup if the engine dies. If you can't steer it at all, you might want to investigate the HMU for something stuck or plugged. The HMU also provides the power assist when steering.
Here's some troubleshooting ideas from the service manual:
Performance Tests
Performance tests of the steering system can be used for a diagnosis of poor performance and to find the source of oil leakage inside the hydraulic system.
Problem: Hydraulic pump makes noise and the steering cylinder rod does not move smoothly.
Probable Cause:
1. Oil level in tank is low.
2. Air in the hydraulic circuit.
3. The pump has too much wear.
4. Loose connection of the oil line on the inlet side of the pump.
5. Viscosity of the oil is wrong.
Problem: Too much force needed to turn steering wheel.
Probable Cause:
1. The metering pump signal pressure relief valve set too low.
2. Leaking final resolver in inlet manifold.
3. Priority spool stuck.
4. Pump oil pressure is low, worn pump.
5. Steering control unit covers are too tight.
6. Steering control unit has defects.
7. Steering cylinder failures.
Problem: Machine turns too slow in both directions.
Probable Cause:
1. Not enough oil flow from hydraulic pump.
2. Operation of inlet manifold and priority valve not correct.
3. Seal leaks in steering cylinder.
Problem: Steering wheel does not return to center position correctly.
Probable Cause:
1. Metering pump covers are too tight.
2. Steering column is not in correct alignment.
3. Restriction between spool and sleeve in metering pump.
Problem: Machine does not turn when steering wheel is turned.
Probable Cause:
1. Inlet manifold and priority valve is stuck.
2. Check valve in metering pump stuck in open position.
3. Steering cylinder has worn parts.
4. Restriction in the steering linkage.
5. Air in the system.
6. Pump operation is not correct.
7. Dirt in the system.
8. Oil level of the tank is low.
Here's some troubleshooting ideas from the service manual:
Performance Tests
Performance tests of the steering system can be used for a diagnosis of poor performance and to find the source of oil leakage inside the hydraulic system.
Problem: Hydraulic pump makes noise and the steering cylinder rod does not move smoothly.
Probable Cause:
1. Oil level in tank is low.
2. Air in the hydraulic circuit.
3. The pump has too much wear.
4. Loose connection of the oil line on the inlet side of the pump.
5. Viscosity of the oil is wrong.
Problem: Too much force needed to turn steering wheel.
Probable Cause:
1. The metering pump signal pressure relief valve set too low.
2. Leaking final resolver in inlet manifold.
3. Priority spool stuck.
4. Pump oil pressure is low, worn pump.
5. Steering control unit covers are too tight.
6. Steering control unit has defects.
7. Steering cylinder failures.
Problem: Machine turns too slow in both directions.
Probable Cause:
1. Not enough oil flow from hydraulic pump.
2. Operation of inlet manifold and priority valve not correct.
3. Seal leaks in steering cylinder.
Problem: Steering wheel does not return to center position correctly.
Probable Cause:
1. Metering pump covers are too tight.
2. Steering column is not in correct alignment.
3. Restriction between spool and sleeve in metering pump.
Problem: Machine does not turn when steering wheel is turned.
Probable Cause:
1. Inlet manifold and priority valve is stuck.
2. Check valve in metering pump stuck in open position.
3. Steering cylinder has worn parts.
4. Restriction in the steering linkage.
5. Air in the system.
6. Pump operation is not correct.
7. Dirt in the system.
8. Oil level of the tank is low.
