Weak steering

[wizard]

I need some help to steer in reverse. I can actually back up, but my left side is weak it yells back at me loud. I had it up on blocks........ let me start at the begaining. It all started when my 731 died on me. I didn't have any hydraulics compleatly dead. I thought it was my pump, so i removed it and was not happy with what i found. The yolk on the eng. side, and the adapter on the pump side were toast, the yolk was compleatly round, and the adapter splines looked no better. After replacing both reinsalled the pump.
This is where my steering problem appeared, I had no steering from left to right in either direction. I had it up on blocks to adjust my steering, got both sides to nuetral, it could get no better, so I thought. After taking off blocks I was testing my luck. I have good luck with the right side, but only 1/2 luck with the left side. It feels weak when I try to steer back with the left lever, foward works fine. This is where I need TAZZAS help it's a 731 relic, could it be my left motor going bad or my reverse replenishing valve for same side. Can the replenishing valve be removed without removing the pump again. As the steering lever linkage are in the way. Exactly which side, of the pump would the valve be. If I'm not mistaken one hose crosses over to both motors. Thanks beforehand.

 

[Tazza]

From memory, the rear section of the pump indeed does controll the left side. There should be a few plugs in the centre of both sections, the ones on the rear half are for the left, the ones on the front half are for the right side. I'm not sure what side of the pump has the replenishing valves, just remove both, the plugs should be above where the hoses join to the pump. When you fiddle with these plugs, make sure you replace the O rings as this section is under extreme pressure, up to 5,000 PSI. Don't mix the springs up either, make sure yo do one plug at a time.
Just what was wrong with the pump? your rotating group was still ok? The yoke should be round, just with a flat section for the shoes of the pistons to run on.
If you need any info on the pump just let me know.

 

[wizard]

From memory, the rear section of the pump indeed does controll the left side. There should be a few plugs in the centre of both sections, the ones on the rear half are for the left, the ones on the front half are for the right side. I'm not sure what side of the pump has the replenishing valves, just remove both, the plugs should be above where the hoses join to the pump. When you fiddle with these plugs, make sure you replace the O rings as this section is under extreme pressure, up to 5,000 PSI. Don't mix the springs up either, make sure yo do one plug at a time.
Just what was wrong with the pump? your rotating group was still ok? The yoke should be round, just with a flat section for the shoes of the pistons to run on.
If you need any info on the pump just let me know.

The yolk is the one that attatches to the eng.connected to the flywheel, and the addapter with splines is attached to the pump. There are two hoses that cross over in front of the pump connected to each pump, as per this diagram http://users.tpg.com.au/tazza_/731 hydrostatics.jpg which seamed to correct my steering problems when I first had my steering problems trying to steer left and right. Can the replenishin valves be removed without disassembling all the steering linkage apart, or splitting up the pumps as I really don't want to remove the pump again. You would not believe the trouble it is to allien the spine shaft to the yolk. The manual says to remove the valves to see if the problems swaps over, but with the linkage in the way on the left side not sure if the valve can be removed. Any magic I should know about would be greatly performed. Thanks Tazza.

 

[Tazza]

The yolk is the one that attatches to the eng.connected to the flywheel, and the addapter with splines is attached to the pump. There are two hoses that cross over in front of the pump connected to each pump, as per this diagram http://users.tpg.com.au/tazza_/731%20hydrostatics.jpg which seamed to correct my steering problems when I first had my steering problems trying to steer left and right. Can the replenishin valves be removed without disassembling all the steering linkage apart, or splitting up the pumps as I really don't want to remove the pump again. You would not believe the trouble it is to allien the spine shaft to the yolk. The manual says to remove the valves to see if the problems swaps over, but with the linkage in the way on the left side not sure if the valve can be removed. Any magic I should know about would be greatly performed. Thanks Tazza.

The valves sure can be removed without pulling the pump out. I can indeed see the linkages being a problem.. Try removing the valves on the left side first, see what they do. Remember not to swap sides with the valves, what you move from the left side of the pump, must stay on the left etc. The springs are a different colour to make sure you don't swap them. You can move them from front to back, just not side to side.
I now understand what you mean, the shaft that connects to the engine, i didn't find it too hard to re-install, laying down in the machine with the engine un-bolted and another person used crow bars to push the engine forward untill it engaged the splines.

 

[wizard]

The valves sure can be removed without pulling the pump out. I can indeed see the linkages being a problem.. Try removing the valves on the left side first, see what they do. Remember not to swap sides with the valves, what you move from the left side of the pump, must stay on the left etc. The springs are a different colour to make sure you don't swap them. You can move them from front to back, just not side to side.
I now understand what you mean, the shaft that connects to the engine, i didn't find it too hard to re-install, laying down in the machine with the engine un-bolted and another person used crow bars to push the engine forward untill it engaged the splines.

I ended up removing the pump again after lossing all power in my steering, so I could do an insp. on the pump. I found the replenishin valves had some minor wear, so I was going to replace them but at 260.+ for the forward and 45.+ for the reverse you could say I reversed my mind. Is it common for this valves to go bad, and is there someplace where I could purchase them at a lower cost.
What happened is the BC just creeps with no power in both directions, and steering in either direction the pump just squeals for mercy. On the vane pump it says to check for wear on the vanes and the block section. what is normal wear or abnormal wear on the block.

 

[Tazza]

I ended up removing the pump again after lossing all power in my steering, so I could do an insp. on the pump. I found the replenishin valves had some minor wear, so I was going to replace them but at 260.+ for the forward and 45.+ for the reverse you could say I reversed my mind. Is it common for this valves to go bad, and is there someplace where I could purchase them at a lower cost.
What happened is the BC just creeps with no power in both directions, and steering in either direction the pump just squeals for mercy. On the vane pump it says to check for wear on the vanes and the block section. what is normal wear or abnormal wear on the block.

You should be able to get these valves from a vickers/eaton dealer a lot cheaper than bobcat. I would doubt its a valve problem causing no power at all. You said there was only slight wear this shouldn't be a prpblem.....
As for wear, all i can say is check for deep scores in the cam ring as i think they call it, light scoring will be fine as the vanes will bed into these marks. Look for scoring on the top and bottom plates too.
You did check the suction line filter? the one in the port block on the hydro pump middle hose on the left? This would cause squeeling but it wouldn't cause any hydraulic problems, just dydrostatic ones.

 

[Tazza]

You should be able to get these valves from a vickers/eaton dealer a lot cheaper than bobcat. I would doubt its a valve problem causing no power at all. You said there was only slight wear this shouldn't be a prpblem.....
As for wear, all i can say is check for deep scores in the cam ring as i think they call it, light scoring will be fine as the vanes will bed into these marks. Look for scoring on the top and bottom plates too.
You did check the suction line filter? the one in the port block on the hydro pump middle hose on the left? This would cause squeeling but it wouldn't cause any hydraulic problems, just dydrostatic ones.

*hydrostatic
I really shouldn't be typing so early in the morning!!!

 

[wizard]

*hydrostatic
I really shouldn't be typing so early in the morning!!!

Yes I did check it, it looked fine but i'm going to replace it anyway. I'll get a hold of vickers on those valves. I also insp. all the vanes and that block section no real abnormal wear. Thanks again Tazza.

 

[Tazza]

Yes I did check it, it looked fine but i'm going to replace it anyway. I'll get a hold of vickers on those valves. I also insp. all the vanes and that block section no real abnormal wear. Thanks again Tazza.

Not a problem.
Vane pumps are very good with holding their pressure through out their life span. When they wear, they just wear out the housing the vanes run on and when they do, the vanes bed in to the new marks. They are very good at this, but their only flaw is low RPM, the vanes don't fully spin out to create pressure, unlike gear pumps.
As for the filter, mine looked clean too, but i got in to it with a can of de-greaser and a pressure washer. I would have replaced it but they didn't have any available for a few days. They were pretty cheap, i would replace it first and if thats no better go the valves as a last resort. I really do doubt it would be the valves just because both sides are dead. Both valves wouldn't just die at the exact same time.
While you have the pump out, replace the bushing for the lift arms that runs under the pump!!! The pivot point is on the chain case, its a swyne to get at with the pump in. This is if you haven't done it already.