Case 1840 Tandem Pump issue after rebuild

[Nick Bartels]

I just finished up rebuilding the tandem pumps on my Case 1840. I also rebuilt the drive motors and replace 19 hoses on the machine. I drained all fluids and replaced all filters. Now that it is all reassembled, I am having issues with the tandem pump. I never get fluid to flow to\from the drive motors. I have fluid at some various points of the pump, like the servo piston covers, but never to the motors. I am confused and frustrated at this point and have no idea where to go next. The Case service manual says to put a gauge on a non-existant port on the pump to check charge pressure, so I am not sure where I need to connect to check my pressures. Any help would be greatly appreciated.

 

[alrman]

Welcome to HEF @Nick Bartels

There are a lot of things that can cause this.
Firstly, what was the reason for your rebuild? Weak drive or no drive?
What did you replace during the rebuild? Was there scoring on the endplates? Were they lapped or replaced?
Did you fit a new charge pump?
Were the new hoses flushed & cleaned before fitting?

'Rebuilding drive motors' - Was there any scoring or wear evident? Did you use genuine seal kits?
There is the removable thrust/end plate inside the end housing - were the two orings replaced there?
Did you time the motors during assembly?

The pressure test ports do exist, you need to remove a plug & install an adapter to carry out the test.

More information is required for anyone to really help you

 

[Nick Bartels]

Reason for rebuild - loss of right hand side forward power after hydraulic oil heated up. I believe this was caused by a missing 1/2" section of piston ring from the servo piston on that pump.
What I replaced - I purchased the seal and gasket rebuild set from a Sunstrand shop here in Kansas City.
Scoring - the valve plates and cylinder blocks had scoring. I lapped everything until the surface was pristine. Went up to 3000 grit.
Charge pump - appeared to be in great shape, reinstalled.
New hoses - Well, I didn't even think to flush the new lines, but the feed hose to the pump and the four hoses from the pumps to the motors did not get replaced. I did flush them before reinstallation.

Drive motors - No scoring evident. Genuine seal kit. I did not remove the thrust/end plate, I did not have the special tool to remove it. The motor was in great condition, so I believed those two orings would be in good condition too. I timed the motors per the directions in the Case service manual.

 

[Nick Bartels]

By the way, thank you for your assistance, I really do appreciate it.

Nick

 

[DIYDAVE]

A simple thought (only kind I am capable of, LOL) take the plate off. look below, to see that you won't be drilling into anything vital, under the plate, then drill and tap the plate, for a pipe plug, into which you can put a guage, for testing...

Of course, take the plate off, and drill with a drill press, to keep debris out of the internals...

 

[Nick Bartels]

Looking through the manual again, I have a bad feeling I may have the charge pump assembled incorrectly... Per the Case service manual, the pin should be at the top, I really think I have the pin at the bottom... Well crap, I guess I am splitting the pumps again.

 

[Nick Bartels]

I realize it has been a while, but I figured I would update my post. I finally had great weather and the time to work on the Case again. Sure enough, I had the stupid charge pump rotated 180 degrees... What a foolish mistake, at least it didn't cause any harm (at least not that I can tell...)

 

[alrman]

Nice to know you got it sorted. Thanks for the update

 

[Nick Bartels]

Well, I have it all back together and now operates like it should! I still need to rebuild the lift and tilt cylinders, but other than those leaking, all seems well. The machine hour meter shows around 4000 hours, but I believe the engine was rebuilt in the last few hundred hours or so. It starts without hesitation even after sitting out in the driveway for 5 months. During the winter, I did go out on a 20F day, without block heater, it started in maybe 8 seconds of cranking. Cost of the machine and all the parts I have bought, I have well under 10k into it. I think I did just fine...