632 weak pump, I think. Thoughts?

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ChevyEd

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Oct 23, 2023
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Hello all. I've done a bit of reading and I think the pump is bad. I'd like to hear your thoughts please. So, I bought a 632, 1978 I'm told. Ford engine. Left side drive is weak, almost no forward power, some reverse power but not like the right side. Right side works good. I tried changing the bronze filter but Bobcat sent the wrong one so I cleaned it with brake cleaner, blew it out with air and let it sit to completely dry. It was easy to blow air from my lungs through it so I don't think that's an issue. lol At the same time, I swapped the high pressure valves and none of that made a difference. So then, I swapped the motor lines at the pump and now everything is reversed and the right side is weak. So that would say the pump is bad and not putting out the pressure for the left side in normal configuration, right? Also, how hard is it to rebuild the pump and what goes wrong inside them to cause this? Any thoughts or resources would be nice. Thanks.
 

brdgbldr

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Jun 1, 2012
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1,239
Hello all. I've done a bit of reading and I think the pump is bad. I'd like to hear your thoughts please. So, I bought a 632, 1978 I'm told. Ford engine. Left side drive is weak, almost no forward power, some reverse power but not like the right side. Right side works good. I tried changing the bronze filter but Bobcat sent the wrong one so I cleaned it with brake cleaner, blew it out with air and let it sit to completely dry. It was easy to blow air from my lungs through it so I don't think that's an issue. lol At the same time, I swapped the high pressure valves and none of that made a difference. So then, I swapped the motor lines at the pump and now everything is reversed and the right side is weak. So that would say the pump is bad and not putting out the pressure for the left side in normal configuration, right? Also, how hard is it to rebuild the pump and what goes wrong inside them to cause this? Any thoughts or resources would be nice. Thanks.
The hydrostatic pump has a number of valves on each side. any one on the side of your issue could be your problem.

Check the parts catalog, search the hydrostatic pump schematic to find the locations and part numbers.
 
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ChevyEd

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Joined
Oct 23, 2023
Messages
7
The hydrostatic pump has a number of valves on each side. any one on the side of your issue could be your problem.

Check the parts catalog, search the hydrostatic pump schematic to find the locations and part numbers.
As far as the replenishing valves, I swapped the forward valves, no change, and looked at the reverse ones. None of them were stuck or had broken springs.
 

River Fluid Power

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Aug 18, 2022
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I would tend to think that one side of the pump has wear and/or contamination damage. Does it work slightly better when it is cold, and get worse as it gets to operating temperature?
 
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ChevyEd

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Oct 23, 2023
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I would tend to think that one side of the pump has wear and/or contamination damage. Does it work slightly better when it is cold, and get worse as it gets to operating temperature That's what I'm
I would tend to think that one side of the pump has wear and/or contamination damage. Does it work slightly better when it is cold, and get worse as it gets to operating temperature?
That's what I'm thinking. I couldn't really say what it's like at different temperatures. I just bought it hoping it would be an easy fix but haven't operated it any more than driving around a little and loading/unloading it. I couldn't get it up the ramps going forward since the left side had no power. Going up in reverse it barely had enough on the left side to make it and stay straight. Left side doesn't even really make the pump whine. Right does for sure.
 

brdgbldr

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brdgbldr

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I didn't. I figured since the right side works good and the problem switched sides when I swapped hoses then it wouldn't be the issue.
Not sure which hoses you are switching. The pump has a relief valve each side. So if you switch the hoses to the drive motors the problem will switch sides.
 
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ChevyEd

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Joined
Oct 23, 2023
Messages
7
Not sure which hoses you are switching. The pump has a relief valve each side. So if you switch the hoses to the drive motors the problem will switch sides.
The hoses to the motors. I first swapped the forward controlling relief valves with no changes. I'm planning on pulling out the pump and checking the relief valve ports and taking the rear pump apart.
 

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