Locating Replenishing Valves on a 753

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Keith

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Sep 28, 2007
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I have a 753 that I believe may have a problem with one of the replenishing valves. I have a service manual but the pictures are not good and the info on the hydorstatic pump is limited. The pump is a Danfoss M91-35916R. As near as I can tell it looks like two of the valves are on top of the pump under the centering plate and it looks like the other two are on the bottom. Can any one tell me if that is correct? If it is correct, is there anyway to get to the valves on the bottom without pulling the pump? Do I have to pull the engine to remove the pump? Thanks in advance for any info!
 

skidboy

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Jan 3, 2007
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What makes you think you had a problem with a replenishing valve ? this would be highly unlikely
 

Keith

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Sep 28, 2007
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What makes you think you had a problem with a replenishing valve ? this would be highly unlikely
Thanks for responding! The unit is a 753 of early 90's vintage as near as I can tell. When the unit is cold it works well. Once it warms up a little (about 5 to 10 minutes) right reverse gets very weak. Left forward and revese work and right forward works but when you try right reverse it does not want to move. It gets weak and then just wants to groan anytime you try right reverse. After it cools for a couple of hours it will work fine again for another 5 to 10 minutes. The manual lists the replenishing valves as a possible cause? Appreciate any advice! - Thanks, Keith
 

Tazza

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Thanks for responding! The unit is a 753 of early 90's vintage as near as I can tell. When the unit is cold it works well. Once it warms up a little (about 5 to 10 minutes) right reverse gets very weak. Left forward and revese work and right forward works but when you try right reverse it does not want to move. It gets weak and then just wants to groan anytime you try right reverse. After it cools for a couple of hours it will work fine again for another 5 to 10 minutes. The manual lists the replenishing valves as a possible cause? Appreciate any advice! - Thanks, Keith
Sounds more like a suction line filter to me. Especially when you say its fine cold but when warm it gets lazy.
 

skidboy

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Sounds more like a suction line filter to me. Especially when you say its fine cold but when warm it gets lazy.
I think you will find that it is drive motor seals.Early machines were prone to exactly this problem.A replenishing valve prob. would be there all the time.
 

Keith

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Sep 28, 2007
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Sounds more like a suction line filter to me. Especially when you say its fine cold but when warm it gets lazy.
Tazza, Thanks for responding! I have searched hi and lo and not found any in-line filters. I have replaced the spin-on hydraulic filter (upper right hand in the engine compartment) The hydraulic schematic in the manual shows one filter in the line from the hydralic tank but there is none there? Any suggestions on where it might be located? Thanks! Keith
 

Keith

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Sep 28, 2007
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Tazza, Thanks for responding! I have searched hi and lo and not found any in-line filters. I have replaced the spin-on hydraulic filter (upper right hand in the engine compartment) The hydraulic schematic in the manual shows one filter in the line from the hydralic tank but there is none there? Any suggestions on where it might be located? Thanks! Keith
Skidboy, Thanks for responding! Once the motor is removed is there a way to verify that the seals are the problem or does the motor just have to be re-built? Thanks, Keith
 

Tazza

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Tazza, Thanks for responding! I have searched hi and lo and not found any in-line filters. I have replaced the spin-on hydraulic filter (upper right hand in the engine compartment) The hydraulic schematic in the manual shows one filter in the line from the hydralic tank but there is none there? Any suggestions on where it might be located? Thanks! Keith
If your manual shows one and you can't find it, its most probably hidden behind a fitting or inside a fitting between 2 hoses. The suction line filters aren't like a regular spin on type filter they are usually bronze and sit behind screw in fittings. These filters are only really there to filter out larger particles, i think they only go down to around 100-200 microns. Basically if say a motor spits its guts out it helps save other parts down the line.
 

skidboy

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Jan 3, 2007
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If your manual shows one and you can't find it, its most probably hidden behind a fitting or inside a fitting between 2 hoses. The suction line filters aren't like a regular spin on type filter they are usually bronze and sit behind screw in fittings. These filters are only really there to filter out larger particles, i think they only go down to around 100-200 microns. Basically if say a motor spits its guts out it helps save other parts down the line.
Its an easy job to strip the motor down,but if you dont feel confident any hydraulic shop will be able to do the job.It should take about an hour to fit a seal kit.I would be very surprised if it needs any more than a seal kit.
 

Keith

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Sep 28, 2007
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Its an easy job to strip the motor down,but if you dont feel confident any hydraulic shop will be able to do the job.It should take about an hour to fit a seal kit.I would be very surprised if it needs any more than a seal kit.
Skidboy and Taza - Thanks for the info! I found one in-line filter. It did not look real bad but looked a lot better after it was cleaned. I replaced the hydraulic filter and draind out the hydraulic fluid. I'm going to try filling it back up with 10w-30 which the manual says is OK. If it still does the same thing, I have found a near-by hydraulic shop that says they re-build the drive motor all the time. All I have to do is take it out of the unit. I will let you know what happens. Thanks again!
 
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