My new trencher attachment has a 3rd hose for a case drain, so I need to add a case drain hookup to the machine. I've found some writeups for other makes and models, but not for the Cat 259b3. Does anyone have any experience with this? Where would be the best and easiest spot on the machine to tap into a drain line? Thanks in advance.
Does anyone happen to have a hydraulic schematic for this machine they'd be willing to share? I'd like to tie the attachment case drain into an existing circuit but I don't know which location would be best. Where do they connect the attachment case drain on the machines with high flow?
Assuming that the Serial Number prefix is YYZ is the S/N above or below 1542.? The hydraulic schematic is different depending which group of machines the S/N falls into.
Above: YYZ03203
I'll send you a PM.
Just make sure its t’eed into somewhere with zero backpressure or directly into the reservoir above the oil level. Most hydraulic return systems on machines have some amount of backpressure and will cause the seals to leak on some hydraulic motors
I is a little slow here, but, isn't the middle port, at the flat face couplings, a case drain circuit?
Mine doesn't have the 3rd hookup. I've only got two hydraulic couplings and an electrical coupling I've never used.
There's a Manual Loader Lowering Valve that connects directly to the drain manifold. It basically allows you to lower the arms manually without the machine running. The current plan is to tie into the low-pressure side of that valve. That seems like the best option to me.
Just to confirm, I tested the pressure on the hose between the lowering valve and the drain manifold. 0 psi with the machine running, so I should be good to go.
I would also check that while activating a function both directions to make sure
Could you tee into where the drive motors case drains enter the hyd. reservoir?
I was able to put a tee on the low-pressure side of the Manual Loader Lowering Valve - basically between the valve and the drain manifold. From there, I ran a hose to the back of the machine, up to the loader arm, and then to the front of the loader arm with the other quick connects. I've just got the hose zip-tied for now. I tested the trencher attachment and everything seems to be working well. I'll keep an eye on it. Thanks for everyone's help, especially @Nige for the hydraulic schematic.
You're welcome, especially seeing as it all worked in the end.
Hi Guys I found this thread as I am trying to do the same exact thing on my Cat 259B3. I would like to install a case drain on a Cat 259B3 skid loader for a fire wood processor. I would really like to tie in the same way @Howey Matt did. I am not in Tennessee right now were the machine is. So I have asked my buddy to get me the serial number for my machine. If there any chance @Howey Matt or @Nige can share a snap shot of the location you tied in on the machine or the schematic and highlight were the low pressure side of the Manual loader Valve is? I would really appreciate that or any help you can give to point me in the right direction where to do this tie in. We were going to pull the tank and add a bulkhead but this seems like a much better way of doing this. Thank you very much Booshy.
Update My Serial number is YYZ05370. Hope this helps @Nige
You has this? You want this?
Sorry for the late reply. Here's how I did mine. I have not had any issues. Here's the manual lowering valve: This is the low-pressure/drain side where you want to tie in: If you follow that drain hose from the lowering value to the bottom of the machine, you'll see it goes into a manifold. I added a tee at the end of the hose right before the manifold. You can see it where my light is shining here: Then I just ran a hose from the tee around to the hookups on the loader arm: I hope this helps. It gave me an excuse to clean the leaves and sludge out of the machine.
@Howey Matt thats what I needed!!!!! Thank you so much for that!!! We found that manual valve and were working to get the parts.
“I spoke directly with CAT Engineering, and they confirmed that Port 7 is the correct place to T into for a case‑drain return. Port 7 is the same return port the drive motor uses, and that’s exactly why CAT approves it — it’s a dedicated low‑pressure tank return. It’s not a pressure line. It’s the only safe location on the machine where a case‑drain line can be combined without creating backpressure. CAT specifically said NOT to T into the upstream drive‑return hose or any other line. The T must be screwed directly into Port 7 on the return manifold — that’s the only spot where case‑drain pressure stays within spec. That’s exactly what they told me. When I cleaned out that compartment, I found that someone had already run a hose to a T at Port 7 exactly the way CAT described, so that’s how I’ll be plumbing mine as well. Just a suggestion food for thought I will come back on here after with a report.