Winter time in Michigan. Yesterday I took a flight in my Cruzer (Viking 130) and it was 21 degs F at 2500'. During cruise (4800 RPM, 105 kias) the water temp decreased (from the higher climb temp) to 146 degs and the 'oil' (gearbox) temp settled at 101 degs. This seems quite cool to me. Is this something to be concerned about?

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Hey Phil, the gearbox can be as cool as it wants. The temperature probe is right up front in the prop blast. Therefore, could read lower than actual on a cold day. Try covering the probe with a rag and some tie wraps before trying again. Before we dive into whether it is too low etc. we need to ensure it is a true reading. The reason we know there is a lot of cold air in that area is because of the low gbox temps which is next to the temp probe for the engine. So your temp. probe is being air cooled, which in the not. -Alissa

Ok, I'll try that and report back (when this storm clears).

So I ziptied a rag around the temp sensor & housing and just took it for a test flight. Level cruise 2500' at 4800 RPM/105 kts @ 14 degs F and the water temp was a solid 169 degs (gearbox temp was 98 degs). Climb temp maxed at 190. So, it looks like those are more normal temps (or are they?) and I should probably install a permanent sensor insulation of some type. Makes me wonder if the higher climb temps of 210 I was seeing during warm weather was actually higher than that. 

I have the DUC prop with the inset spinner & ~3/4" space all around the spinner. Anyone else with that setup seeing similar temps?

The thermostat will hold it at 180F, so whatever you see less than that is due to air flow over the sensor housing. For the instrument and the ECU to see more accurate temperature blocking the sensor housing from the incoming air would be a good move. With the type of cowling with type of spinner you have it cools that housing even more. 

If it were mine, I'd verify the accuracy of the sensor, and test the thermostat.

Our 750 STOL w/ Viking 130 has a Warp Drive prop with small spinner.  We also have 1/2 to 3/4" space around the spinner.  Our engine has two coolant temperature sensors, and both plug into the same casting.  One is for the ECU, and the other is for our GRT EIS.  Our EIS sensor is screwed into a plug further behind the gearbox.  

Not sure if the Viking View uses the same sensor as the ECU, but if it does, and that's what your using, then perhaps relocating the sensor to the other plug behind the gearbox would help.

We've operated our engine on the ground at low rpms for tests with 18ºF ambient temperatures, and the coolant temperature settled around 175ºF.  Since we typically lay up the aircraft during the winter months, it's never been flown when this cold.  

We've also pulled our thermostat a few times for testing and modifications.  Very simple to do.  Assuming you have the same thermostat, it's set to be open at 172.4ºF.

Thanks for the feedback. The Viking View uses its own water temp sensor in the same place where you have your GRT sensor so no repositioning is possible. It seems the best solution is insulating the area. Attached are a couple of before and after photos of my insulating effort. It seems that this is the best solution for the most accurate readings. I'm wondering now if my summer time temps were not accurate due to this airflow cooling effect. The highest I saw my water temp go on aggressive extended climbs was 210, but was it really higher than that? I plan on keeping that insulation in place in the summer to see if it makes a difference. I do fly mine throughout the year, so far the coldest has been 2 degs F.


Seems to me, even if the ambient temperature is 21F, the engine's thermostat should be regulating the coolant temperature to within normal operating limits.  

Hello Phil,

I have the Zenith Cruzer with the Viking 130 in Wisconsin. Two questions: do you pre-heat the engine when below freezing and how did the Viking cabin heater work for you in the cold temps?

No preheat as my plane is in a heated hangar (60 degs F). If I were in an unheated hangar I would not bother with any sort of pre-heat since the Viking uses 0w-20 oil which flows well in the coldest of temps. I mean, how often would you pre-heat your car? I might consider pre-heat if the temps were consistently -15F or below.


I have the Cruzer with Viking 130 in Arkansas. I haven't used the cabin heat much as I'm flying on good days right now and with just about any sunlight on cold days the cabin stays reasonably warm due to the greenhouse effect of all those windows. I have turned it on a few times on cold days though and noticed a slight temp increase around the feet, but not much else. On a long XC that might be of significance, but I have enough drafts that the overall cabin temp isn't affected much.

I don't preheat. My wife drives a Honda Fit with the same engine and neither of us has never had any cold-start issues.

I forgot to reply about the Viking heater - I've got my cabin pretty sealed up and have found the Viking heater does pretty well at keeping it relatively warm, although I need to make some airflow directors to bring the heat more forward instead of straight down as it does now. I can't imagine flying with temps in the 'teens or below without some sort of cabin heat!


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