water in rear engine/pressurized case

[atsiii]

I'll try to keep this brief, but will provide more details if anyone thinks they can help. I have a 1969 T337D with a JPI engine analyzer. I am based at 6200 MSL, and constantly fly in very cold air.

I had been seeing evidence of water in the rear engine (rust and water on dip stick) for some time. I was also fighting oil leaks from places where there should not have been oil pressure (through bolts at the top of the case, etc.). The front engine was dry and showed no evidence of water. My typical cruise is 28” and 2400 rpm, at which time the JPI indicates front oil temps around 150, and rear around 180. This agrees with the Cessna gauges. Cylinder and EGT temps are all normal (300 - 340, 1410 - 1510). The engine has GAMI injectors installed. I cruise at peak plus 75.

A M-20 Model 300 Air/Oil separator was installed a few years ago on the rear engine, and attached to the side of the oil filler pipe directly in the path of the rear engine intake air flow. No oil separator was installed on the front engine. I began to suspect that the case was not venting properly through the oil separator, and thus retaining water vapor. I theorized that if this moisture was then freezing inside the separator, it might further restrict airflow and proper venting through the separator, thus creating pressure in the case resulting in my strange oil leaks. The only whistle hole seemed (please excuse my ignorance!) to be mis-located-- as it was downstream from the separator at about push rod level. Thus, all venting had to go through the oil separator, which was getting hit with all the cold intake air. There did not appear to be any other means vent if the separator froze or created back pressure.

To test this theory, I removed the oil separator and ran hoses from the breather on the oil filler pipe and the breather coming up out of the case, to the rear vent hole by the rear prop. I flew one hour and landed to find all sorts of water and thick mustard colored oil/water mixture dripping down from the rear vent hole. However, I did not have oil leaking from places where there should not have been oil pressure, and there was no water on the dipstick. I cleaned everything up and another one-hour flight produced the same results. I therefore thought my theory might be correct, and that more flying would burn off the remaining accumulated water.

However my next flight was 3.5 hours in very cold air. Upon landing it appeared that the vent hoses had once again frozen and pressurized the case. As I took things apart, I literally found tablespoons of water and the thick mustard colored oil/water goop in the breather hoses. Pulling the rear breather up out of the case, I can look down into case and still see suspended droplets of water in the oil. The oil itself looks normal, both in the case and on the dipstick.

My quesitons: Have you ever seen such a thing? Does any of this make sense? Can my theory about freezing and back pressure be true? Or might this have to do with the rear oil temp control? How best can I get rid of the residual accumulated water in the engine? Has this likely done great damage to the 850 hour engine?

Thanks in advance, Allen