Hi, all --
I was assured at some point in ancient history that the CHT sensors on our 2015 912ULS, SN 6784449, were the same as the oil temp sensor, but upon inspection I just can't convince myself of that. I reviewed the IM 72-00-00 Figs 2 & 3 on pg 3 (2015-01) and confirm that ours point off to the side at 30ish degrees. They are bolt heads on rings and do not have a tab sticking out. They also contact coolant. Am I insane, or are these in fact "new style" and therefore useless to cannibalize for oil temp troubleshooting?
We have a SkyReach BushCat with two Sertrab 10-vane (50-110-7612) coolers. In general, the BushCat tends to be overcooled; metal tape across the top cooler is standard in cold weather. [SkyReach has not yet approved a thermostat, much to our dismay.] She's never given us a problem in the Georgia, USA summers even a bit past 100F. Water usually runs 190-200F and oil flirts with the 220s, and I have our temp alarm set for 230F to start paying attention. [We also thought that 250F is redline; I must have misread that since it's 285F and we see discussion of running at 250F happily.]
Last year we (Laura and I are both LSR-Ms for airplane, and we maintain our S-LSA planes) did the 5-year rubber swap, which was the first time to our knowledge the oil system was completely drained after the SkyReach build fill. Everything was awesome all last typical hot summer, though, as well as through the winter. Then, suddenly, we hit hot oil temps.
We run [93 octane no-Ethanol] MoGas and suspect that we still had winter blend in hot May temps. Moving to 50/50 with AvGas took care of the apparent vapor lock and inability to start when hot that was also a new experience, but even straight AvGas didn't keep temps down in the most recent tests. Between then and now we've flushed both coolers, checked all lines for kinks (all sharp turns are tube rather than hose, which is helpful), confirmed that no routing has been bumped near hot metal, ans tried various tests. While she is a little cooler after the flushes, which we believe from the pump strain early to smooth running maybe 4-5 seconds later did appear to push out some goop, we are still warmer than in the past. I can easily push her through the 230s with just 2k-3k feet of climb, and even in level flight at cruise RPM she eventually gets up there -- whereas previously we could climb as hard as we like, and cruise at nearly WOT for 90 minutes straight, all summer long. Something has changed, and we don't like not knowing :-(
Back to sensors ... I was going to swap in a cylinder sensor to see if it's the device, but that doesn't look to be an option. Short of ordering another, which appears to be anything from "pricy" to "OMG that's a much as gasoline these days" and also takes time, I've also seen reference to measuring resistance and want to go and read up on that (that was harder
https://www.rotax-owner.com/en/general-tech-discussion/9285-oil-temp-sensor-resistance
than it sounded). Beyond that, though ... any testing or troubleshooting suggestions?
TIA
