Potential Causes for Coolant Leak inflight

[bdbogle]

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!

I actually found that comment in the checklist to be, almost, funny. If I was in a DA40NG, I would have ridden that engine to landing in and watched the oil temp like a hawk. But in a '42, with the coolant temps continuing to climb even after a power back, I figured that securing the engine was the most prudent thing to do. Don't feel like burning a motor up and causing a really expensive AOG situation when I could easily make it back on a single. To be honest, I didn't really see much of an increase in oil temp, but I wasn't going to wait for a warning to happen. I just know that hot coolant, leads to hot oil, which leads to engine seizure. Hopefully know more next week.

[MackAttack]

Please keep us all posted! Thanks!

[ememic99]

But in a '42, with the coolant temps continuing to climb even after a power back, I figured that securing the engine was the most prudent thing to do. Don't feel like burning a motor up and causing a really expensive AOG situation when I could easily make it back on a single. To be honest, I didn't really see much of an increase in oil temp, but I wasn't going to wait for a warning to happen. I just know that hot coolant, leads to hot oil, which leads to engine seizure.

Few years ago I had a broken coolant hose clamp which led to coolant loss. Consequently the oil temperature started to rise and I was able to keep it in yellow region just briefly lowering the power. When it approached red region I shutdown affected engine and started drift down to save the altitude just in case. ATC cleared space for me and I landed OEI after some 30 minutes. The final result was fried coolant pump - according to my mechanic I should’ve immediately gone for shutdown rather than trying to run the engine without coolant.

[bdbogle]

Please keep us all posted! Thanks!

Looks like they are going to send a pressure testing kit from FTW to test the engine and see if they can find where the leaks are coming from. Should know more next week.

[bdbogle]

Looks like they found the source of the leak. They found a leak in the thermostat housing. According to the DSC, apparently they occasionally warp and leak. Should be case of replacing the housing and refilling the system.

[michael.g.miller]

Please be careful with accepting this explanation as verbatim. The thermostat itself should NOT warp, this is not expected behavior and likely indicates a different issue with your engine. You can try having them replace it, but expect to loose your coolant again in the next 100-200 hours.

[bdbogle]

Please be careful with accepting this explanation as verbatim. The thermostat itself should NOT warp, this is not expected behavior and likely indicates a different issue with your engine. You can try having them replace it, but expect to loose your coolant again in the next 100-200 hours.

Thanks for the info. Will keep an eye on it. Doubt I'll get more than another 100hrs on it as I've got a '62 scheduled for delivery in September.

[bdbogle]

Finally got the plane back from maintenance and the main culprit was a leaking o-ring at the bottom of the thermostat housing that goes into the engine block. The thermostat was replaced and all is good. There was a also a loose pressure relief valve that leaking coolant as well that was tightened back down and stopped that leak.

[michael.g.miller]

Yep I have seen that failure mode before. For anyone reading please do not think replacing the O-ring and thermostat will solve it. This is just a short-term band-aid, and you most likely will loose all your coolant again through the same O-ring.