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912 overheat suggestions

  • john folsom
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1 year 4 months ago #13425 by john folsom
john folsom created the topic: 912 overheat suggestions
I have a Rotax 912 engine, with adjustable prop. The engine is about 4 years since new, about 1500hrs.

I was climbing out(prop full rpm, engine dropped back a little from full power) with my CFI on a check ride and about 1500ft agl(1600ft msl) with outside temp around 80f the CHT began to rise near 260f, the oil temp was following it by about 20f or so. I have a 253F coolant temp sensor and it did not go off. We level out and temps were not dropping. We did a 180 back to the airport cutting throttle back increasing airspeed to 110kts or so did not cool it appreciably. Cutting to idle, gliding back upon landing the temps had lowered. Went back to the hangar to check coolant level, etc. Everything looked good. Did a couple of laps in the pattern(up to 800agl) and similar symptoms persisted. At this point it had Evans waterless coolant, the coolant was flush and 50/50 replaced it as per mechanics recommendation.

Another day, temperature inversion 75f or so on the ground 90f at 1500agl. Climbing out at around 1800ft agl CHT to about 255, Coolant light goes on and oil temps around 240f or so. Leveled off and turned around again, cooled down on power-off approach. Did a couple of laps around the pattern, at around 700agl, it would heat up. I have been climbing out 75kts when I would like to be around 65kts. Straight and level flight at 90kts did not lower the temps

One person got out of the plane to lower weight, and tests repeated with similar issues. Performance is fine and can climb pretty much at book before beginning to overheat. I am sure temps would continue to rise if power wasn't cut and would rise much faster if climbed at Vx.

Fresh gas, Sport plus oil, sensors checked out, new plugs 30hrs ago, Radiators looks clean/fins straight, all cylinder heads approx same temperature when cowling removed. Engine runs and idles as other 912 I have flown.

Mechanic is not a Rotax expert and is out of ideas and there are no Rotax specialists at the field.

Thanks

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1 year 4 months ago #13426 by Roger Lee
Roger Lee replied the topic: 912 overheat suggestions
Was any maint. done on the engine prior to this? Evans carries a 20-30F heat penalty so that was good that it was replaced.

With that many hours and the increase in coolant temp and with some of the other checks done I would pull the radiator and have it flushed.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-574-1080 Home (TRY HOME FIRST)
520-349-7056 Cell

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1 year 4 months ago #13428 by john folsom
john folsom replied the topic: 912 overheat suggestions
Roger thanks for your reply,

Looking over the logs, no major maintenance done, beside all the required. 200hr/annual for airframe done 30hrs ago 78/80 all around. It had it's annual done this winter and is the first time flying in warm weather since.

Plugs looked a little on the lean side to me but mechanic said no problem.

I'll have him change/flush the fluid and the radiator again.

It had it's annual done this winter and is the first time flying in warm weather since.

Thanks again.

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1 year 4 months ago #13430 by Roger Lee
Roger Lee replied the topic: 912 overheat suggestions
I mean professionally flushed and cleaned and not just drained. Reducing prop pitch and angle of attack can help to.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-574-1080 Home (TRY HOME FIRST)
520-349-7056 Cell

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1 month 2 weeks ago #17162 by James Depfer
James Depfer replied the topic: 912 overheat suggestions
Roger,

I have been using Evans coolant since 2012 and have come close to overheating a few times. The extra 20-30 degrees will probably help me with this marginal situation.

Three years ago in post # 7231 you has indicated the steps you use to flush water in preparation for Evans. I was wondering if those same procedures could be used to flush Evans (minus the adding of Evans Prep).

Could I use that procedure to switch to water coolant, and is there anything extra I would need to do to remove all of the Evans ?

Thanks, Jim

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1 month 2 weeks ago #17165 by Roger Lee
Roger Lee replied the topic: 912 overheat suggestions
Hi James,
My bet is switching back to a 50/50 coolant and dropping those extra 20F - 30F degrees in extra heat retention with Evans will work well for you.
A couple ways to dump your old coolant. You can use the screw on the back side of the water pump if you like. Most times I can't get to that. What I do find fast and efficient will sound goofy, but it works like a charm. I slide back the lower hose on the coolant radiator with a pan under it and let it drain for a couple seconds. Then I keep the pan there and pop the top off the black expansion tank on top of the engine and allow more coolant out.
Here comes the fun part. :) LOL
I toss a rag over the radiator tube and hose while they are still disconnected. Then I just cup my hand around the expansion tank and blow hard down through the expansion tank's mouth. I blow hard 4-5 times. This removes all the coolant in the system. If you have a thermostat you may have to remove another hose to drain that short section. If there is no thermostat your cooling system will be practically free off all coolant. When I do a 5 year hose change I have to remove the coolant or it would make a major mess all over the floor. This method clears the entire system. If you fail to place a rag over the coolant radiator tube and hose you will blow coolant all over when you blow down through the system. It is an open system throughout. It vacates coolant in all hoses and areas.
I know this may sound like an odd way to drain the coolant, but it is fast and effective.
Then just add your 50/50 back to the engine.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-574-1080 Home (TRY HOME FIRST)
520-349-7056 Cell

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1 month 2 weeks ago #17168 by James Depfer
James Depfer replied the topic: 912 overheat suggestions
Roger,

Thank you for the information. I'm getting things together to do my 5-yr rubber replacement next month, and decided this is a good time to switch to 50-50 coolant.

Jim

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4 weeks 20 hours ago #17346 by ENRICK FOURNIER
ENRICK FOURNIER replied the topic: 912 overheat suggestions
yes evan give penality, dexcool is the way to go, did you see in your manual if The Rotax 5 year rubber replacement covers all fuel, oil and coolant lines as been performed,

some people inspect the hose from the outside and looks great, like we did on one of my aircraft, we have the same issue as you just mention, so we remove the radiator, and find inside of them smal ruber piece, the came from the coolant interior hose are dissetagrating them self, but before this, with flush the coolant, do some oil change, and else, before we came to this... if you can inspect your hose interior, and inspect the interior of the rad, on my side, i have to replace them, they was cloged....

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2 weeks 11 hours ago - 2 weeks 8 hours ago #17492 by William Stilley
William Stilley replied the topic: 912 overheat suggestions
On my 912 ULS coolant temperatures were in the middle of the green, until a week ago. Then while still in the pattern, cht went up to 120 C. Drained the coolant, took the thermostat out, rinsed it and put it in boiling water. It opened like it should, so I installed it and refilled the coolant. In the pattern, the cht went to 130 C, so I landed. Drained the coolant and found a very fine sand colored material settling to the bottom of the container. I have found this material every time I have drained the coolant (4 times now). This time I saw coolant had leaked out of the overflow bottle and what appears to be the water pump. The coolant tank on top of the engine was dry on the outside. I have the oversize radiator from Kitfox Aircraft. The engine was manufactured in 2006 and has total time of 70 hours. Any ideas about cause or fixes?
Last Edit: 2 weeks 8 hours ago by William Stilley.

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