Cat D6T. S/N KJL01024. Complaint of a transmission oil leak. Got to the unit and found it was leaking out of the transmission/torque converter breather. (They are tee’d together beneath the cab). Removed the lines and checked for blockages - none found. When I removed the line off the torque converter, oil started pouring out, indicating the torque converter is overfilling/not draining. Performed both inlet and outlet pressure checks. Inlet relief valve pressure was 60PSI (max 95PSI as per cat) and the outlet was 40PSI (spec is 60PSI). Disassembled and inspected the outlet relief and it was clean and moving freely, no broken springs etc. I replaced the transmission oil cooler as it was very dirty and I suspected it may be restricting the outflow of oil from the torque. No change to the issue after that. Any ideas?
Is there a screen in the drain line from the converter housing.?
How about a failure of scavenge section of transmission pump
The scavenge pumps job is to remove oil from torque housing that leaks out of the torque excess leakage caused by bad seal rings cracked impellor or pot Knowing how cat plumbs the lines i would doubt the screen is in a inlet line I would think the line that goes to pump is on the suction side of the pump
How fast does transmission temperature rise? And does the transmission oil temperature rise without the machine moving?
From reading here and there, and asumptions from other older models... Breath line from the transmission case alone, i see no condition besides high oil level that causes spill through breath system. TC breath case may indicate excessive TC drum leak, and or the scavenge pump is not able to empty the case. The TC case has a screen. Adding to this, if converter is leaking beon limits TXM temperatures will certainly rise as mentioned.
I'd suggest a check of the small screen in the converter scavenge line first. It is located in the end of the converter scavenge hose sandwiched between the end of the hose and the converter housing. If it is clear then the scavenge section of the powertrain oil pump would be the next candidate.
Just curious am I the only one that got this on a e mail alert ? There is a screen but it is on the inlet side of the torque in the line that connects the pump to the torque. I’m not sure a scavenge pump failure fits my symptoms as I seem to have too much oil in the torque. Either way, the inlet relief valve would limit the pressure and my pressure reading off that valve was in spec. I am thinking something is preventing it from draining properly. The oil that exits the torque goes through the outlet relief valve, then the trans cooler, then back to the lubrication manifold. At the lubrication manifold, the oil then combines with oil that has bypassed the torque converter.
If the screen is OK and the pump section is OK, then you will have to remove the torque converter and inspect it. If the torque converter is leaking oil inside, the pump section will not have time to pump it out. And one of the symptoms is the transmission heating up quickly. The transmission temperature arrow on the instrument panel shows the temperature in the torque converter.