L4200 hydraulics problem

[Rodent]

Hi, I’m new to kubota and recently got a L4200 tractor. It has two hydraulic circuits at the back (I think, as there is four quick-connects). One circuit works both ways (extends and retracts a hyd top link no problem) but the 2nd circuit only seems to work in one direction. I can extend my hydraulic top link on this circuit, but to retract it I need to swap the hoses over. is this normal or is there something wrong?
thanks,
Will

 

[TheOldHokie]

Hi, I’m new to kubota and recently got a L4200 tractor. It has two hydraulic circuits at the back (I think, as there is four quick-connects). One circuit works both ways (extends and retracts a hyd top link no problem) but the 2nd circuit only seems to work in one direction. I can extend my hydraulic top link on this circuit, but to retract it I need to swap the hoses over. is this normal or is there something wrong?
thanks,
Will

Let's just say it's uncommon. Typically the outlets are double acting and you seem to be describing a single acting circuit. We're are the valves located and can you post a picture of them?

Dan

 

[Rodent]

Let's just say it's uncommon. Typically the outlets are double acting and you seem to be describing a single acting circuit. We're are the valves located and can you post a picture of them?

Dan

Hi Dan, thanks for your reply. Sorry i didnt respond quicker, your message went into my junk folder, probably because its my first message on orangetractor. I’ll try and upload some photos later today. The 4 quick connects are mounted in a block at the back right side above the right side link arm. There are then 4 hoses going to what looks like a spool valve mounted above the rear axle (right side again), then a single hose i think fitted into the hydraulic pump.
thanks, Will

 

[TheOldHokie]

Hi Dan, thanks for your reply. Sorry i didnt respond quicker, your message went into my junk folder, probably because its my first message on orangetractor. I’ll try and upload some photos later today. The 4 quick connects are mounted in a block at the back right side above the right side link arm. There are then 4 hoses going to what looks like a spool valve mounted above the rear axle (right side again), then a single hose i think fitted into the hydraulic pump.
thanks, Will

Thats the standard outlet arrangement but according to the parts book there should only be the 4 hoses going to the rear.

If there is a fifth hose in the mix somebody has added something. Given the behavior possibly a tank return to use one of the valves on a single acting cylinder. Pictures should help clarify.

Dan

 

[Rodent]

Thats the standard outlet arrangement but according to the parts book there should only be the 4 hoses going to the rear.

If there is a fifth hose in the mix somebody has added something. Given the behavior possibly a tank return to use one of the valves on a single acting cylinder. Pictures should help clarify.

Dan

Hi Dan, i think it might be making a bit more sense with some photos attached. On the spool/circuit that appears to be behaving like a single acting cylinder, one hose has been tee’d and the 5th hose routes inboard to the top up point. There is a 1/4 turn valve where the hose meets the top up point and that valve is open. Does that make sense to you? Should i close the valve on that hose?
Thanks,
Will

 

[TheOldHokie]

Hi Dan, i think it might be making a bit more sense with some photos attached. On the spool/circuit that appears to be behaving like a single acting cylinder, one hose has been tee’d and the 5th hose routes inboard to the top up point. There is a 1/4 turn valve where the hose meets the top up point and that valve is open. Does that make sense to you? Should i close the valve on that hose?
Thanks,
Will

Exactly what I suspected. The tee creates a direct path to tank and with the shutoff open you can not build pump pressure on that outlet. Close the shutoff snd you should get "normal" double acting operation.

Now why is it plumbed like that? It's a clean well fone modification and the perp undoubtedly knew what he/she was doing. I can think of two good reasons:

1. The valve was being used with a single acting cylinder and the bypass prevents deadheading the unused outlet against the pressure relief when the cylinder was retracted
2. The outlets were being used with a hydraulic motor and the bypass is a direct to tank motor return.

Dan

 

[Rodent]

Exactly what I suspected. The tee creates a direct path to tank and with the shutoff open you can not build pump pressure on that outlet. Close the shutoff snd you should get "normal" double acting operation.

Now why is it plumbed like that? It's a clean well fone modification and the perp undoubtedly knew what he/she was doing. I can think of two good reasons:

1. The valve was being used with a single acting cylinder and the bypass prevents deadheading the unused outlet against the pressure relief when the cylinder was retracted
2. The outlets were being used with a hydraulic motor and the bypass is a direct to tank motor return.

Dan

Hi Dan, thanks very much for your help with this. My guess is maybe the previous owner had a tipping trailer with a single acting cylinder on that circuit. If closing that valve is all it takes to get that circuit double acting then i’ll be super pleased. Really appreciate your help on this one.
will