DA40NG Coolant Leak and ECU A Failure
Posted: Sat Nov 20, 2021 3:05 pm
I've got a tale of woe to share that I though you all might find interesting/useful. I'll be sure to post updates on root cause, and how this gets resolved.
Long story short: I've got a new DA40NG that rolled off the line in July of 2021. Since the first day there has been ongoing small amounts of coolant that I occasionally observe under the engine cowling during pre-flight. I discussed this with my instructor and the company I bought and maintain the plane through initially, and it was not considered a cause for concern.
Fast forward until a week ago, and suddenly I am experiencing COOL LVL warnings prior to the coolant reaching normal operating temperatures, which is perhaps not unexpected since the coolant has likely dropped low enough to trip the sensor prior to heating up. The plan was to get the plane to Toronto (a 2 hour flight) this morning so it could be checked by a mechanic familiar with the Austro engine. I never made it. Although the COOL LVL warning did permanently go out once the coolant came up to temperature, the ECU check failed with an ECU A caution, which will now simply not clear, regardless of running the checklist to clear the ECU failure on the ground and restarting the plane several times. In the timeline below I've got video's linked of the COOL LVL light going on and off, the ECU A failure refusing the clear, as well as coolant actively leaking after the plane was put in the hanger this morning after the aborted flight.
Here's the detailed history:
July 24, 2021. On the second day of my transition training my instructor and I noticed coolant on the floor of the hanger. To my recollection it was not a large amount, and did not raise significant concern at the time; just something we would keep an eye on. This small amount of coolant leakage was something that we continued to observe from time to time during the transition training.
August 16, 2021. The plane is serviced at the London factory. Although I had discussed the coolant leak with the company managing my maintenance, it does appear as a listed item on the maintenance sticker from that servicing. It seems possible the coolant system was never inspected.
August 16 – November 13th, 2021. Every once in a while I would notice a few drops of coolant on the ground during my pre-flight. In my mind this had (incorrectly) become normalized, and I didn’t think too much about it. At no time did I ever observe the COOL LVL warning illuminate.
November 14th, 2021. During my taxi prior to takeoff I noticed the COOL LVL warning temporarily illuminate. This seemed to happen briefly during turns, and immediately extinguished. The warning did not occur during the rest of the flight, despite my doing several stalls, slow flight, and slips in both direction.
November 15th, 2021. During my walk around I noticed a few drops of coolant under the rear cowling again. Upon starting the engine the COOL LVL warning illuminated and this time, for the first time ever, it stayed illuminated. I decided to let the engine warm up a bit and see what happened. After about 5 minutes, as the coolant temperature started to approach the green zone, the coolant warning started to go on and off every few seconds. The frequency of this seemed to diminish the warmer the engine got. I suspect that had I let the engine/coolant come fully up to temperature, the light would have stayed off. Regardless, it did not seem wise to embark on a night flight with the coolant apparently approaching a critical level. You can find a video here (https://mail432com-my.sharepoint.com/:v ... g?e=gilGo0) of the light coming on and off with the coolant at 56 degrees. Note all videos are 1080p, so if they seem of low quality you might need to download them before playing them to get the full quality. Also note that there was an ECU A warning soon after the engine was started, but the normal process of clearing the ECU caution resolved this issue immediately (i.e. place the ECU voter switch to A for five seconds, then back to auto).
November 20th, 2021. The plan was to perform a prolonged run up to allow the coolant to come fully up to temperature, hopefully clearing the COOL LVL warning, and then fly the plane to Buttonville for servicing. During initial run up the COOL LVL light warning illuminated as expected. However, once the coolant level reached about 73 degrees, the COOL LVL warning ceased to occur. At this point I move on to the ECU check. Prior to the ECU check neither the ECU A or B warnings were illuminated (i.e. the ECUs appeared healthy). During the ECU check I immediately observed that the ECU A check did not sound normal. In a normal ECU check the load would increase to just above 50%, then temporarily reduce to about 30%, prior to increasing again to 50%. The engine would normally return to idle and repeat the process (presumably on the other ECU). On this ECU check the initial increase to 50% load occurred as expected by then it simply stayed at 50% load during the time it should have temporarily reduced. The engine then went to idle as normal and the second sequence of 50%-30%-50% sounded completely normal. Upon completion of the ECU test the ECU A caution was illuminated and stayed permanently illuminated from this point on, regardless of attempts to clear it including restarting the engine twice. You can see video of me attempting to clear the ECU A caution here (https://mail432com-my.sharepoint.com/:v ... Q?e=7zGlKK). I cancelled the flight, and put the plane back in the hanger.
November 20th, 2021. About 10 minutes after putting the plane back into the hanger following the aborted flight to Buttonville I noticed a small amount of coolant on the ground. I was able to capture video of coolant slowly dripping out of the engine cowling, which you can watch here (https://mail432com-my.sharepoint.com/:v ... g?e=jYHpw3).
I'll keep you posted as the saga progresses!
Long story short: I've got a new DA40NG that rolled off the line in July of 2021. Since the first day there has been ongoing small amounts of coolant that I occasionally observe under the engine cowling during pre-flight. I discussed this with my instructor and the company I bought and maintain the plane through initially, and it was not considered a cause for concern.
Fast forward until a week ago, and suddenly I am experiencing COOL LVL warnings prior to the coolant reaching normal operating temperatures, which is perhaps not unexpected since the coolant has likely dropped low enough to trip the sensor prior to heating up. The plan was to get the plane to Toronto (a 2 hour flight) this morning so it could be checked by a mechanic familiar with the Austro engine. I never made it. Although the COOL LVL warning did permanently go out once the coolant came up to temperature, the ECU check failed with an ECU A caution, which will now simply not clear, regardless of running the checklist to clear the ECU failure on the ground and restarting the plane several times. In the timeline below I've got video's linked of the COOL LVL light going on and off, the ECU A failure refusing the clear, as well as coolant actively leaking after the plane was put in the hanger this morning after the aborted flight.
Here's the detailed history:
July 24, 2021. On the second day of my transition training my instructor and I noticed coolant on the floor of the hanger. To my recollection it was not a large amount, and did not raise significant concern at the time; just something we would keep an eye on. This small amount of coolant leakage was something that we continued to observe from time to time during the transition training.
August 16, 2021. The plane is serviced at the London factory. Although I had discussed the coolant leak with the company managing my maintenance, it does appear as a listed item on the maintenance sticker from that servicing. It seems possible the coolant system was never inspected.
August 16 – November 13th, 2021. Every once in a while I would notice a few drops of coolant on the ground during my pre-flight. In my mind this had (incorrectly) become normalized, and I didn’t think too much about it. At no time did I ever observe the COOL LVL warning illuminate.
November 14th, 2021. During my taxi prior to takeoff I noticed the COOL LVL warning temporarily illuminate. This seemed to happen briefly during turns, and immediately extinguished. The warning did not occur during the rest of the flight, despite my doing several stalls, slow flight, and slips in both direction.
November 15th, 2021. During my walk around I noticed a few drops of coolant under the rear cowling again. Upon starting the engine the COOL LVL warning illuminated and this time, for the first time ever, it stayed illuminated. I decided to let the engine warm up a bit and see what happened. After about 5 minutes, as the coolant temperature started to approach the green zone, the coolant warning started to go on and off every few seconds. The frequency of this seemed to diminish the warmer the engine got. I suspect that had I let the engine/coolant come fully up to temperature, the light would have stayed off. Regardless, it did not seem wise to embark on a night flight with the coolant apparently approaching a critical level. You can find a video here (https://mail432com-my.sharepoint.com/:v ... g?e=gilGo0) of the light coming on and off with the coolant at 56 degrees. Note all videos are 1080p, so if they seem of low quality you might need to download them before playing them to get the full quality. Also note that there was an ECU A warning soon after the engine was started, but the normal process of clearing the ECU caution resolved this issue immediately (i.e. place the ECU voter switch to A for five seconds, then back to auto).
November 20th, 2021. The plan was to perform a prolonged run up to allow the coolant to come fully up to temperature, hopefully clearing the COOL LVL warning, and then fly the plane to Buttonville for servicing. During initial run up the COOL LVL light warning illuminated as expected. However, once the coolant level reached about 73 degrees, the COOL LVL warning ceased to occur. At this point I move on to the ECU check. Prior to the ECU check neither the ECU A or B warnings were illuminated (i.e. the ECUs appeared healthy). During the ECU check I immediately observed that the ECU A check did not sound normal. In a normal ECU check the load would increase to just above 50%, then temporarily reduce to about 30%, prior to increasing again to 50%. The engine would normally return to idle and repeat the process (presumably on the other ECU). On this ECU check the initial increase to 50% load occurred as expected by then it simply stayed at 50% load during the time it should have temporarily reduced. The engine then went to idle as normal and the second sequence of 50%-30%-50% sounded completely normal. Upon completion of the ECU test the ECU A caution was illuminated and stayed permanently illuminated from this point on, regardless of attempts to clear it including restarting the engine twice. You can see video of me attempting to clear the ECU A caution here (https://mail432com-my.sharepoint.com/:v ... Q?e=7zGlKK). I cancelled the flight, and put the plane back in the hanger.
November 20th, 2021. About 10 minutes after putting the plane back into the hanger following the aborted flight to Buttonville I noticed a small amount of coolant on the ground. I was able to capture video of coolant slowly dripping out of the engine cowling, which you can watch here (https://mail432com-my.sharepoint.com/:v ... g?e=jYHpw3).
I'll keep you posted as the saga progresses!