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I took delivery of (slightly used) 62.093 on Tuesday and flew off my insurance requirements with the CFI who made the delivery flight. Everything was perfect until I dropped him back in Ft Worth and made the 3.5 hr return flight to CO last evening. All indications in the cockpit were in the green the whole flight, but this morning there was blue coolant on the hangar floor under the right engine.

After seeing photos of the uncowled engine, Premier’s maintenance managers in FL and TX concur that the pressure relief valve released some coolant on the flight home last night. Why!? is a different question: I didn’t exactly push the engines, climbing at 92% and cruising at 8-10,000’ at 7.8 gph a side. We’d put about 12 hours on the engines since Monday’s 100-hr without any issues.

A test run this afternoon gave a R COOLANT LO warning on engine start, which went away when the coolant temp reached about 42° C.

I’m told that as long as I don’t see a low coolant warning on takeoff I will be able to fly the plane to maintenance. Does the brain trust here agree?

FWIW, my used DA42NG had apparently been spitting coolant out of the relief valves on both engines for a while prior to its annual in November/December. Both valves were replaced at that time. Apparently there's a newer/better version of the coolant tank for the DA42NG; it's possible that your DA62 already has that. I would consider adding some coolant to that tank prior to taking it to maintenance, but I guess you're probably OK as long as you don't have a LO reading and the temp stays in the normal range.

Chris wrote: ↑Fri Jan 22, 2021 11:24 pm I would consider adding some coolant to that tank prior to taking it to maintenance, but I guess you're probably OK as long as you don't have a LO reading and the temp stays in the normal range.

On the DA62, the coolant system is safety wired shut and coolant level is not an owner maintenance item.

Sure, but it seems like a local shop could probably handle that fairly easily. Or does it require Austro certification just to add coolant?

Chris wrote: ↑Sat Jan 23, 2021 1:08 am Sure, but it seems like a local shop could probably handle that fairly easily. Or does it require Austro certification just to add coolant?

Don’t know the answer, and I also don’t have the coolant spec. When I asked Arapahoe Aero’s Diamond guys, they didn’t know, either...since they aren’t yet Austro certified.

I need answers to all these questions, since from what I’ve learned in the last 24 hours, from multiple sources, a coolant release (as distinguished from a leak) is not that unusual.

Learning about Austro engines myself, I found this in the AFM:


And this on eBay:
Maybe?

This is why you have two engines, right? I mean, as long as it takes off you can probably make it to the shop.

(My original DA40 salesman was in a DA42 1.7 and lost one engine over KSBA. He turned around and flew back to KLGB on the other engine. When I was surprised he said, "You've been flying on one engine for ten years!" So, touché.)

COOLANT LO message is not uncommon for a cold Austro engine. It does need to extinguish once warmed up. I flew my DA62 for about 50 hours with that issue on my left engine, and it always went out prior to the oil temp rising to within the green band. Serviced at annual, I have not had an issue since.

You have the newer coolant tank. Mine has it, and it is 42 units older than yours.

As a new owner I clearly have a lot to learn. It was disconcerting to find blue fluid on the hangar floor after my first solo x-c, and to see the mess it made inside the engine compartment and out on the nacelle and wing root when the relief valve opened up in flight for no good reason that I could fathom.

The good news is that with the help of Premier and the owners here I have learned more about my new baby; that Xerex G48 50/50 is available at a local auto parts place for $18/gallon; and that Diamond has a phone number my local shop can call to obtain guidance when they service the coolant system.

I’ll try to stop overthinking this and get back to enjoying flying.

Congrats on your DA62!

I've had exactly the same issue you mentioned TWICE on my DA62 right engine -- this is a common problem.

What's frustrating is after you finish cleaning up the mess of blue coolant sprayed all over your engine, when you remove the safety wire and "radiator cap" to check the coolant level (on a cold engine), you'll find it's all the way to the top of the tank -- way above the coolant level indicator inside the tank. So you can't just add more fluid to get rid of the low coolant annunciation message.

The good news is that you can fly the plane AS-IS with no problem because the L/R COOL LVL annunciation on the PFD goes away as soon as the engine warms up before takeoff (I've flown my DA62 all the way across the US and back with it that way).

The first time this happened I let my shop take care of it when my plane was in for its annual inspection last year. But after it happened a 2nd time I decided to fix it myself: The "secret" is to remove the bleed screw located on the coolant system aluminum tube on the top/front of the engine (very easy to access with the cowlings off). This will let fluid/air out and depressurize the system enough that the coolant level will drop inside of the coolant tank -- allowing you to add coolant antifreeze and distilled water up to the level indicator. So far, this seems to have fixed the problem (got fingers crossed) -- no more R COOL LVL annunciation before engine start.

I never had this problem the 4 years that I owned a DA42-VI with the older model coolant tank topped by an old-fashioned radiator cap (no safety wire). It seems that only the newer tanks (with safety wired cap) have the problem of expelling coolant out their relief valve.