Kubota B1550D hydraulic fluid in engine crankcase.

Porcello garage

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Kubota B1550D
Jul 4, 2026
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Enfield ct
Hey guys, Im new to the forum and looking for some thoughts and advice. My B1550 doesnt have any visible hydraulic leaks, my hydraulic fluid after a few hours needs to be topped off, and my engine crank case keeps filling past the full line on my dipstick. I'm making an eduacated guess that my issue is a seal on the engine driven hydrualic pump. I did see another forum on here that someone was having the same issue on a b1550 hst and the seal and o-rings fixed the issue.
My question is what seal(s) am I replacing would it be p/n 31381-76190( Ref 80). Or is it other o-rings too? I will order the hydrualic pump to gear pump holder gasket (ref 20). Do I need to order the gasket from gear pump holder to crank case or no becuase that will not need to be removed? Is there any other things I need to buy? Thanks in advance!





kubota b1550.png kubota b1550 2.png
 

TheOldHokie

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Hey guys, Im new to the forum and looking for some thoughts and advice. My B1550 doesnt have any visible hydraulic leaks, my hydraulic fluid after a few hours needs to be topped off, and my engine crank case keeps filling past the full line on my dipstick. I'm making an eduacated guess that my issue is a seal on the engine driven hydrualic pump. I did see another forum on here that someone was having the same issue on a b1550 hst and the seal and o-rings fixed the issue.
My question is what seal(s) am I replacing would it be p/n 31381-76190( Ref 80). Or is it other o-rings too? I will order the hydrualic pump to gear pump holder gasket (ref 20). Do I need to order the gasket from gear pump holder to crank case or no becuase that will not need to be removed? Is there any other things I need to buy? Thanks in advance!





View attachment 176619 View attachment 176622
Shaft seal #80. It can be replaced without taking the pump apart.

Dan
 
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Russell King

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There are also some o-rings at the points where the pipes enter and exit the pump. They are probably fine to reuse but I personally replace them anytime I break an older connection just for peace of mind.

added on edit

Those joints look like banjo bolts so instead of o-rings there will be two crush washers per bolt (4 total).
 

Russell King

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Crush washers are the #110 and #120
 

Porcello garage

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Kubota B1550D
Jul 4, 2026
32
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Enfield ct
You have to remove/disconnect both top and bottom pipes. Replace all the crush washers - 110, 120 and the ones on top.
Im not sure what you mean sorry, so I need to removed the hyd selector and the pump so should i order qty 1 of 110 and 120 and then order 130 o-ring for bottom pope? Do I need the 020 o rings?
 

TheOldHokie

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Im not sure what you mean sorry, so I need to removed the hyd selector and the pump so should i order qty 1 of 110 and 120 and then order 130 o-ring for bottom pope? Do I need the 020 o rings?
The hydraulic pipes and the outlet block are attached (sandwiched) to the pump with two banjo bolts. You should replace all of the washers and o-rings between those components. You can get away with reusing the rubber seals but not the copper washers
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Porcello garage

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Kubota B1550D
Jul 4, 2026
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Enfield ct
Thank you so much guys, where do you guys recommend I buy or download the service manual. Does kubota have a shop manual with removal and install instructions with proper torques? Or am I just a spoiled avaition mechanic with manuals like that lol. I have never removed anything on my b1550 so I want to make sure I do it right.
 

TheOldHokie

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Thank you so much guys, where do you guys recommend I buy or download the service manual. Does kubota have a shop manual with removal and install instructions with proper torques? Or am I just a spoiled avaition mechanic with manuals like that lol. I have never removed anything on my b1550 so I want to make sure I do it right.
Free download:


You probably wont find tightening torques but this is not an aircraft.

Dan
 
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Porcello garage

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Kubota B1550D
Jul 4, 2026
32
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Enfield ct
Hey all, So I finally got all the parts, and I got the pump removed. Is this damage or machined on the pump shaft and the bearing on the engine side?

I also don't see any visuable damage to the shaft seal. But going to replace it anyways whats the best shop practice to pull the seal screw in a few screws and pull on it?

Thanks in advance!

@TheOldHokie
@Russell King


IMG_0801.jpeg


IMG_0797.jpeg earing on the engine side?
 

TheOldHokie

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Apr 6, 2021
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Hey all, So I finally got all the parts, and I got the pump removed. Is this damage or machined on the pump shaft and the bearing on the engine side?

I also don't see any visuable damage to the shaft seal. But going to replace it anyways whats the best shop practice to pull the seal screw in a few screws and pull on it?

Thanks in advance!

@TheOldHokie
@Russell King


View attachment 177559


View attachment 177558 earing on the engine side?
Thats damage to both the tang on the pump and the drive slot.

Dan