loss of radiator coolant

[montanapilot]

I own an Astore with a 914. During preflight today, I saw that the coolant level was way down - almost to the bottom of the reservoir. I've owned the airplane since new, for a year and a half, and the coolant level has never gone below what it was when I took delivery. I was closely monitoring the temps on my last flight (Saturday) because I'm dealing with cold Montana weather that varies 15 degrees and we're taping the radiators to keep temps up and monitoring the amount of tape needed for various temps. Temps were actually below what we want during my last flight. My mechanic is going to go through the engine tomorrow, but he wonders if the fact that I keep a Tanis engine heater plugged in all of the time would cause the coolant to boil over. Before I began keeping the Tanis plugged in, I spoke with Tanis and with my mechanic, and both said that it's okay to do that. I've kept the Tanis plugged in for many consecutive days before and have had no problem. However, I wanted to check to see if anybody has had this problem and determined that it was caused by the Tanis. 

[Cluemeister]

My coolant level dropped this year, much to my surprise. Turned out upon investigation that the clamps securing the coolant hoses to the radiators had loosened slightly, and the coolant had slowly dripped out into the inside of the cowling. Tightened them up, added coolant, no issues since then.

[Flocker]

I've experienced the same thing as Cluemeister. I recommend tightening the clamps at every oil change.

[Glenn]

Ditto. Same experience.  My first clue was red-orange stain on the bottom inside cowling.  It wasn't a big enough leak to see the level decrease in the reservoir. 
It took a bit of time to find which clamp was loose.  Now I check them all at every oil change.  

[montanapilot]

I spoke with Lockwood this morning. Their thought was that the engine is always pressurized and when the weather turns cold and, therefore, the engine as well, the pressure is reduced and the coolant drops back into the engine. So, my mechanics checked everywhere for leaks, and non found. They then drained all of the coolant, pressurized the system, and found no leakage anywhere. We refilled the coolant. I ran the airplane for a couple of minutes, and it remained at the same level. I then flew for a half hour or so, landed, and checked the coolant level. It hadn't budged. So, it might be the "engine getting colder" effect, but one of the Rotax mechanics that I work with isn't completely convinced that it still might have something to do with my keeping the Tanis plugged in all the time. Although I've been doing that for the past month, it had never been plugged in as long as it had been when I experienced the problem. So, I am going to have the Tanis turned on the morning that I intend to fly.
Thanks so much for all of the responses.

[ChrisConnor]

I've had a slight coolant leak at the lower radiator hose, due to loose clamp, two or three times since I've owned my P92. That's over the course of six years. It so slight that I don't notice it until the reservoir gets low. I top it and and then tighten the clamp. Takes a long time to get loose again. Nothing more than a minor annoyance. 

[ChiMike]

When I’ve got my coolant level ‘at the line’ (914) I’ve noted coolant droplets inside my cowling. Almost as if it was over pressure when under load.

I didn’t top the coolant off back to the line—cleaned everything up—and haven’t had any issues since. I did double check connections and tightness—all seemed nominal.

[TiPi]

One thing to remember with the Tecnam overflow reservoir is that it is very small (P92 use a brake fluid reservoir). The cold level needs to be at the lower end, about 20mm above the bottom. With a hot engine, the level will then be near the top of the bottle. If you fill the reservoir to the mid-level, it will overflow when hot. The cold level also changes some 5-7mm between summer and winter. Most other 912 installations use a 0.5lt reservoir, the Tecnam one is only about 0.25lt.
Tighening ALL hose clamps (fuel, oil, coolant) is an annual/100h requirement and should not be missed. Also replace the radiator cap at the 5-yearly rubber replacement (BMW P/N 17112345074).

[montanapilot]

What was interesting about this is that the amount of coolant in the reservoir had only dropped a very small amount, yet there was a puddle of coolant on the hangar floor - the amount on the floor was way more than the amount that the coolant had dropped in the reservoir.

[montanapilot]

They were able to tighten clamps, one right above some coolant residue on the inside of the cowl. I'll test fly it tomorrow and we'll see what happens. Hopefully, they've got it. Thanks to all for the postings.

[Cluemeister]

Yup, the good news is the pink/orange stuff leaves a nice trail on the cowling to diagnose the source!

[Glenn]

And the bad news is the red/orange trail is difficult to get off.

[montanapilot]

That particular shade of orange does not go well at all with the blue and the white.