Tad Olmsted Posted April 26, 2011 Report Share Posted April 26, 2011 I posted this on another site and have been getting some feed back from some guys with older SW's with no oil temp bypass thermostats. According to Rotax, the oil temperture must reach 191 degrees F to boil off any moisture in the oil. As we all know, moisture is a byproduct from combustion and ends up in our oil. This is why there is a white milky film on the bottom of our oil can cap. Tape on the oil cooler is not a good idea, and here is why: I recently put an oil cooler bypass thermostat on a customers Tecnam Bravo IAW Tecnam letter of authorization. I ran the engine for 20 minutes and never saw the temp get above 170, but it did warm up very quickly. When my customer went home he reported that he never saw 191 degrees during the flight home. He achieved over 200 degrees with tape and wondered why the thermostat didn't work. Here is the answer: The oil temp is indicated at its coolest point (on oil pump when the cool oil comes out of the cooler) and reads low. So if the guage says 170 degrees at its coolest point, what is the oil temp at its hottest point??? There is no way of knowing that. If you use tape on the cooler be advised that your oil at its hottest point could be out of tolerance and do some serious damage to your engine. The tell tale sign of proper oil temp is easy to see. Just take the oil can cap off and flip it over to see if there is any milky white film on it after a flight. If there is none , then your oil might be good to go, if there is, then consider an oil cooler thermostat. It is self regulating and I have installed several that work wonderful. Now for all you guys who have an oil cooler bypass: This is the reason your Dynon probably never gets into the green range on your EMS. I know we all want to take a quick glance at the panel and see all green. Unfortunately it will always read low, but rest easy, it is working properly. Total cost is around $600.00 to retro fit an oil cooler bypass thermostat, material and labor. Hope this helps. Link to comment Share on other sites More sharing options...
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