Not familiar with the DA42/62 engine compartment, but most relief valves/fluid overflows in aircraft engine compartments are routed by drainage tubes to near the bottom of the compartment. On the DA40-180, offhand I can think of:
None of these are allowed to just vent directly into the compartment, they are connected by tubing to the vent stack, so they can coat the bottom of the fuselage instead.
Just wondering about the engineering rationale of letting coolant overflow directly into the engine compartment.
Just a guess, but coolant is non-flammable and non-corrosive and so letting it spray around the inside of the engine compartment, willy-nilly, presents no particular hazard.
CFIDave wrote: ↑Sun Jan 24, 2021 11:30 pm
Congrats on your DA62!
I've had exactly the same issue you mentioned TWICE on my DA62 right engine -- this is a common problem.
...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).
Thanks, CFIDave. I look forward to many flying adventures with the new bird.
I'm not at my hangar, but I did take some photos yesterday with the cowlings off. In those photos I don't see the bleed screw you refer to, but is that maybe because I'm looking at the coolant expansion tank and not the engine block?
BTW, why is my engine oil so black, even just a few hours out from a 100hr oil change? Is that a diesel thing, or does the oil start out black (I haven't cracked open my sole 'spare' liter of Diesel Ultra)?
photoSteveZ wrote: ↑Mon Jan 25, 2021 2:28 am
Just a guess, but coolant is non-flammable and non-corrosive and so letting it spray around the inside of the engine compartment, willy-nilly, presents no particular hazard.
True, but coolant overflow drains in my cars are also vented overboard via hoses. If this coolant venting is a common occurrence with the diesel engines, I would look into attaching my own hose (as an approved minor mod, of course).
Dave would know better for the DA62, but the DA42 AMM shows two bleed nipples in the system. One is on the aluminum tube from the water pump and the other is on an aluminum tube forward of the thermostat valve.
FWIW, my engine oil is also pretty much black just ~10 hours out of annual. I'm guessing it's typical since it seems to be expected in diesel car engines as well. I feel like I'm starting over from scratch with these Austro engines after years of running the IO-360-M1A.
Ah, there it is! We found another screw in a smaller aluminum tube at the rear of the engine, but elected not to mess with it when we serviced the tank. It took nearly a quart of coolant, which was more than anyone led me to expect. Test run, uncowled: no issues. Test flight: no issues.
I learned during the Austro/DA42 Maintenance course at the London, Ontario factory that the mechanic servicing the coolant system needs to massage all of the blue coolant lines as the coolant system gets refilled to get all air out of the system, then do it again after an engine run, then top off. Probably more effective on a warm day. The factory uses a pretty awesome vacuum system for the initial fill which totally prevents this issue, but would be cost prohibitive for your (or any) Diamond Service Center to purchase, and nearly impossible to replicate in effectiveness by any other means.
This might be the most often reported gripe about the Austro engine after the first 100 hr service
