Potential Causes for Coolant Leak inflight

[bdbogle]

Christmas Eve at about 8:30pm, I had just flown to Louisiana to drop off my niece and her son and was departing when at about 3000ft on the climb-out, I got a Coolant High-Temp warning. It had blown right through the yellow and was into the red at this time. I pulled the power, leveled off and waited to see what happened - it continued to rise. So before things got any worse, I shut the engine down. There was no Coolant LVL low warning or any indication that the oil temp got high. Engine feathered as expected and I setup for an ILS approach into BTR. Once parked, I restarted the engine and the coolant temp was low as expected after being cooled off for about 20 minutes. Once the coolant got to the normal operating temp, the coolant temp rose very quickly at about 30% power and quickly got into the "warning" area of about 95 degree. I pulled the power back to almost idle and it settled back down after a few seconds. I shut it down and was going to pull the engine covers off. Prior to unbuttoning it, I noticed coolant dripping from the bottom of the cowling. Took everything off and there was coolant from the top of the engine block to parts down low. Something sprung a leak but I couldn't find any indication of a lose clamp, busted cooling hose, or anything else. Engine oil looked normal as well. Ended up renting a car (Thanks to BTR Ops for giving me a ride to the terminal) and driving 3+ hours home.

Any ideas from the DAN brain trust as to what might be the cause? Water Pump failure? Something with the thermostat? Something else? Plane is currently AOG at BTR so hopefully there's someone around that can work on them!

[FlyingPenguin]

Hello bdbogle,

Sorry to hear your problem here. Based on your description, my guess is that you have a stuck thermostat in the closed position, and somehow leaking as well. Not sure about that. Take a look at the location of the thermostat. Would this be the area you noticed coolant on the engine?

[Chris]

There are a few other threads related to coolant leaks with these engines. Here's one of them.

The more common problems seem to be related to the pressure relief valves or air in the system. Your symptoms seem a bit more serious to me.

[bdbogle]

Hello bdbogle,

Sorry to hear your problem here. Based on your description, my guess is that you have a stuck thermostat in the closed position, and somehow leaking as well. Not sure about that. Take a look at the location of the thermostat. Would this be the area you noticed coolant on the engine?

There was a good deal of coolant under the thermostat but I couldn't tell if there was any leaking around it. Though it was a night and it was a bit difficult to see everything clearly. I did get a call from the on field shop and they were closed for this week so we'll find out more in a week or so.

[Fred Claus]

Sorry to hear this. You may consider calling the techs at Take Flight aviation. I just had a coolant line blow apart on me a few weeks ago and an accompanying false engine fire indication. They are the ones who fixed it up as it was their plane (311LH). I know this is different but I only mention them because they’re quite well versed in austro engines.

[mfdutra]

Take a look at the location of the thermostat.

Where did you find that manual? I’d love to have these diagrams.

[Chris]

I'm not sure if they are still working, but this other thread has some links.

[FlyingPenguin]

Take a look at the location of the thermostat.

Where did you find that manual? I’d love to have these diagrams.

Hello Marlon,

Check your email please.

Thanks!

[MackAttack]

Brian, feel free to give me a call. I had a R engine coolant temp master warning in early December (caused me to abort an Angel Flight with passengers as it occurred about 15 minutes after departure from KIWS), which appeared on my investigation to be a sensor-related issue. I took the plane to Premier for annual a few days later and it started out normal but on descent into KFTW the R ENG COOLANT temp spiked again into the red. Haven't heard back from Premier on the cause. I didn't notice any leaking or dripping from the engine even after a few days in the hangar. Your situation sounds different. I didn't shut down the engine (interestingly, the checklist doesn't call for a shutdown - it says to be prepared for an "imminent engine failure").

I've had now 3 sensor failures during my first year of ownership so don't rule out a sensor-related issue. Will be curious as to what you find - nobody is around this week to really do much digging/repairing...

Cheers!

[michael.g.miller]

Take a look at the location of the thermostat.

Where did you find that manual? I’d love to have these diagrams.

The Austro engine documentation and software are now available free of charge with no login required: https://partners.diamondaircraft.com/s/files