1968 JD 400

[robinfields24]

Aloha! Newbie to TBN.

I am having a problem with hydraulic fluid not returning to my main hydraulic pump. I rebuilt the main pump, so it is working. I am not sure if the problem is my transmission pump, a clogged screen (inlet screen?), or a valve that is stuck. The tractor was operating normally for the last 3 years. I want to check every possible problem before I have to split the machine in half to check the transmission pump. Any helpful ideas or tips? I am having a hard time locating the inlet screen (screens fluid before the transmission pump?). The repair manual says the screen is located under a plug behind the transmission-hydraulic filter? I have pulled all plugs in the area and found nothing. Any help you can give would be much appreciated. I can post pictures if necessary.

 

[mmurphy]

The screen you are looking for is on the right side of the tractor ( as you are sitting on the seat). It points out to the side. (horizontal) Look at where the filter that goes up in to the casing, it should be by it.

Is there oil in the small tank by radiator?
Does your model have reverser?
Are you sure pump is getting stroke?
I maybe a little slow getting back to you.

 

[robinfields24]

Murphy, thank you for your reply.

Yes, I have a reverser.

There is oil in the reservoir only if I add it. If I fill the reservoir with oil, I can run the machine and use all the implements (loader, backhoe, steering) so I assume that the main hydraulic pump is pushing oil (in stroke?) However, once the main hyd. pump uses all the oil in the reservoir then the implements stop moving and I can't steer. The reservoir does not refill-all the fluid seems to stay in the casing.

I have opened a few lines and changed both filters (return filter and trans-hydraulic filter) but it has not helped. I have no knowledge of valves, but it seems like something is blocking oil from returning to the main hyd. pump.

As for the screen, I have looked in that area (right side, next to trans filter) and I only find a large plug that connects to the return filter with a short hose. I pulled that plug but did not find a screen. I will try to post a picture of the area in case I am missing something.

Thanks for your help. hopefully we can figure out why the oil will not cycle.

 

[mmurphy]

Another thought comes to mind. I believe the pressure relief valve to the full flow filter will dump the fluid back in to the case. I am only going by memory (that ought to scare you) but pressure to the reverser should be aprox 150 psi, and from there to the main pump should be 60 psi.

 

[whu1957]

Hi Bill here, I have a 68 jd400 also, I'm getting hydraulic oil in my motor filling to where it comes out the dip stick, ??? anyone know why this might be happening?

 

[Tx Jim]

Are you sure it's hyd oil or is it diesel?? It would be very difficult for hyd oil to travel to engine. Does hyd oil leak out the drain hole in the bottom of clutch housing?

 

[whu1957]

Yes positive, I put new seals and a new fuel injector pump and fuel pump in, was fine and then bamm hydra oil in the motor. Crazy, everyone I talk to say's the same, I'm pulling the pressure valves out next. I don't know. Keep me in mind.

 

[Tx Jim]

OK my old pee brain just remembered how hyd oil can get into engine DUH!!!!!!. Early 400's have a power steering pump bolted to RH frt of engine and the seal failed.

 

[whu1957]

I will look into that today, I will get back to you, thanks.

 

[whu1957]

#21 is that the seal I see in the book.