Front Engine Oil Temperature?

[Mich3773]

During a recent front propeller overhaul (mandatory every 10 years in Canada) excessive corrosion was found inside the front propeller. Looking back over engine monitor data, I found that the front engine oil temperature is rarely above 130 F, even during the summer. I assume water vapour condensing and accumulating in the oil is the source of the corrosion. There's never been any evidence of water in the oil on the dipstick or in oil samples. CHTs and EGTs are within normal ranges. I'm thinking the front engine oil cooler is over-sized, there's too much airflow through it, and a plate needs to be installed on the outlet to reduce the air flow and increase the oil temperature.

What range of front engine oil temperatures do you see? Your thoughts?

[edasmus]

I too had my front prop fail an overhaul 5 years ago in May of 2020 for the same reason as you. The blades were OK but the hub failed due to corrosion. I could never find a serviceable hub so ended up purchasing a new front prop identical to the original for about $15500 USD at that time.

As for oil temp, yes my front runs cooler than the rear by about 20 to 30 degrees F. CHT's do also but all within accepted and reasonable norms. For what it's worth, my rear engine outlasted my front engine when I overhauled the front in 2020 and rear in 2021. The rear engine was removed from service and overhauled "just because," not for any other reason. (I know, I know, we can debate why I elected to do that.... )

As for managing oil temp, I have frequently believed the C337 would definitely benefit from a pilot controlled mechanism to adjust airflow into the oil coolers during flight as outside air temps in my opinion have a significant impact on the oil temp we see on our panels.

I have had good success (not perfect success) covering the oil coolers nearly completely in the winter time, partially (about 50%) in the spring/fall, and leaving them uncovered in the summer months. Outside temps at and below freezing, I leave them nearly completely covered (about 90%). From freezing to about standard temp or slightly above (0 C, 32F to 15 C, 59 F), the oil coolers are about 50% covered, and a few degrees above standard they are uncovered. (Your mileage may vary on this.) Using this technique I can keep the oil temps in the vicinity of 180F on the gages. As I said, definitely NOT perfect but in most cases the oil temp is between 140F to 180F on the gages. Some adjustments in individual installations will likely be needed to stay in the vicinity of target oil temps.

Talk to your maintenance staff about techniques to restrict airflow to the oil coolers. I know that my POH references "winterization kits" that Cessna provided back in the 1970's to accomplish this. My technique is extremely simple and can be accomplished in a minute both install and removal. In fact occasionally on a cool morning, I'll start with oil cooler restriction and then remove the restriction for subsequent flights as the outside temp warms up. Hope this helps. BTW, my airplane is a 1973 C337G.