Serial number: DX200548 My Cat 299D2 XHP is leaking oil from the end of the case drain connector when it is running, even when nothing is attached. If I depress the end of the connector a low pressure stream will shoot out. My question is should I have any pressure at all at the case drain connector? I thought oil only flowed back through this connector when the case drain line of an attachment (like my mulcher) is attached to it. I can get a new case drain connector or new o-ring, but just wanted to verify that I don't have another problem. I just wanted to note that every few months I have to pull the male high flow connector and put a new o-ring on the end. The o-ring goes bad and pressure is released back through the case drain line causing oil to be released through the case drain relief valve of my mulcher. My grapple also slowly closes on its own when this o-ring needs replacing. This isn't the problem here as I just replaced the o-ring.
Did you ever figure out the issue I’m having the same problem
You will have pressure on the case drain. The case drain on mine dumps into the hydraulic oil cooler making is subject to whatever pressure is pushing oil through the oil cooler before returning to tank. I have changed couplings on the case drain coupling before due to leaking. In reference to your o-rings failing on the high flow. I had a terrible time with high flow couplings and ultimately removed the block and just put couplings on the ends of the hoses. While not perfect this eliminated most of my issues.