Rotax 912 overheating???

H. Paul Shuch is a Light Sport Repairman with Maintenance ratings for airplanes, gliders, weight shift control, and powered parachutes, as well as an independent Rotax Maintenance Technician at the Heavy Maintenance level. He holds a PhD in Air Transportation Engineering from the University of California, and serves as Director of Maintenance for AvSport of Lock Haven.

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rcpilot
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Rotax 912 overheating???

Postby rcpilot » Sun Sep 25, 2016 7:49 am

So I'm trying to get ready for my check ride. My instructor is out of town and I'm doing some solo work. This particular day it was a bit busy(I was 4th in line on the taxi way). While waiting I notice that my water temperature gauge is almost pegged in the red area. I go to the end of the taxi way and turn around. I pull into the run up area and since there was a couple people behind me I shut her down and wait for them to pass. I then taxi back to my parking spot. I don't see any signs of overheat as in steam or coolant spraying out. The reservoir bottle is full. I take the cap off the expansion tank, no steam or anything, I see fluid but don't know if the level is correct. I'm thinking that maybe it's not drawing fluid from the reservoir but don't know. Mechanic is out-of-town. Any suggestions/ideas while I'm waiting for my mechanic to look at it? Oh, it's a Rotax 912.

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Re: Rotax 912 overheating???

Postby roger lee » Sun Sep 25, 2016 9:14 am

Some planes will over heat from idling too long. If you taxi out and have a normal wait time and no issues in flight then it was just too long an idle. The engine gets little to no air movement depending on the plane and sitting there during a long idle.
It's not time to worry. Go do your flight test first. It's too early to tell.
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3Dreaming
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Re: Rotax 912 overheating???

Postby 3Dreaming » Sun Sep 25, 2016 9:21 am

Does it have a coolant thermostat? I have seen those stick before causing an over heat situation.

Also I have been told by Dean Vogel that an easy way to tell if it has been to hot is to look at the CHT probe. The center will melt when it gets to warm. Maybe Roger can confirm this.

rcpilot
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Re: Rotax 912 overheating???

Postby rcpilot » Sun Sep 25, 2016 10:18 am

Yeah, don't have a CHT gauge. I know "normally" it goes slightly into the red before takeoff and then cools down as I'm flying. This though has gone way into the red nd that's why I'm concerned. It's a little cooler out maybe I'll give it a try, just stay in the pattern and see what it looks like.

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MrMorden
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Re: Rotax 912 overheating???

Postby MrMorden » Sun Sep 25, 2016 11:14 am

What type of airplane? My 2007 CTSW never even gets close to overheating on the ground, even running/taxiing for 30min or more in Georgia summers. The only time It ever gets hot is in a hard climb, and even then it manifests as high oil temp, my CHT/coolant temps stay well in the green. I'm sure baffle/cooling/cowling designs make a big difference with these engines. It sounds like yours might have an inadequate radiator or insufficient cooling air over the cylinders.
Last edited by MrMorden on Mon Sep 26, 2016 11:56 am, edited 1 time in total.
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rcpilot
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Re: Rotax 912 overheating???

Postby rcpilot » Sun Sep 25, 2016 11:38 am

MrMorden wrote:What type of airplane? My 2007 CTSW never even gets close to overheating on the ground, even running/taxiing for 30min or more in Georgia summers. The only time I ever hot is in a hard climb, and even then it manifests as high oil temp, my CHT/coolant temps stay well in the green. I'm sure baffle/cooling/cowling designs make a big difference with these engines. It sounds like yours might have an inadequate radiator or insufficient cooling air over the cylinders.


Zenith 601. This is a new problem. Have over 60 hours in since I bought it and never had this happen before.

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FastEddieB
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Re: Rotax 912 overheating???

Postby FastEddieB » Sun Sep 25, 2016 12:08 pm

rcpilot wrote:
Zenith 601. This is a new problem. Have over 60 hours in since I bought it and never had this happen before.


If both the "spider" and the overflow tank are full with the appropriate coolant, I'd start by examining all the coolant hoses, looking for places they might have kinked.
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3Dreaming
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Re: Rotax 912 overheating???

Postby 3Dreaming » Sun Sep 25, 2016 6:13 pm

rcpilot wrote:Yeah, don't have a CHT gauge. I know "normally" it goes slightly into the red before takeoff and then cools down as I'm flying. This though has gone way into the red nd that's why I'm concerned. It's a little cooler out maybe I'll give it a try, just stay in the pattern and see what it looks like.


Unless you have the new style head with the temp probes on the top of the cylinder at an angle you are measuring CHT, even if your gauge calls it water temp. The old style just screws into the aluminum head. The new style actually is located in the coolant.

Do you have a picture of your engine installation from both sides?

rcpilot
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Re: Rotax 912 overheating???

Postby rcpilot » Sun Sep 25, 2016 7:50 pm

3Dreaming wrote:
rcpilot wrote:Yeah, don't have a CHT gauge. I know "normally" it goes slightly into the red before takeoff and then cools down as I'm flying. This though has gone way into the red nd that's why I'm concerned. It's a little cooler out maybe I'll give it a try, just stay in the pattern and see what it looks like.


Unless you have the new style head with the temp probes on the top of the cylinder at an angle you are measuring CHT, even if your gauge calls it water temp. The old style just screws into the aluminum head. The new style actually is located in the coolant.

Do you have a picture of your engine installation from both sides?


Hmm, I'll have to look at that. Hopefully I can get my mechanic to look at it sooner than later.

rcpilot
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Re: Rotax 912 overheating???

Postby rcpilot » Wed Sep 28, 2016 2:12 pm

Well, the problem has been solved. Apparently the pickup tube in the reservoir bottle became disconnected and was no longer pulling fluid into the cooling system and hence it was low. Mechanic flushed the system, filled it up with new coolant, fixed the reservoir bottle and all is good. And according to him there is no thermostat in the system.


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