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DA62 coolant leaks

Posted: Wed Jun 13, 2018 9:08 pm
by jprhode
Hi,

Anyone else have issues with coolant leaking? I have, especially on longer flights and higher altitudes. My plane (S/N 62.010) had the original style coolant reservoirs, which I guess had issues - leaked both from the caps and pressure relief valves. We switched those tanks out for the newer style (introduced sometime before 030), which have a more robust cap. The caps no longer leak, but the valves still do, although very slowly. And, frankly, I don't see how they wouldn't leak - the valves are right at the fill line. The current plan is just let it leak down and see if it stops before the low coolant warning comes on. I don't really love that plan.

Any similar experience?

thanks
Jason

Re: DA62 coolant leaks

Posted: Wed Jun 13, 2018 9:20 pm
by rdrobson
I have about 100 hours on my a/c but haven't seen anything. Are the leaks observable during pre/post flight and if so where or is your only symptom the warning light?

Thanks,

Ron

Re: DA62 coolant leaks

Posted: Wed Jun 13, 2018 11:28 pm
by jprhode
This far I haven’t had the warning come on.

I can see the right one leaking in flight - with the new tanks it’s just a little bubbling at the rear seam of the inboard nacelle cover. I’ve found this to be quite disconcerting to passengers...

It’s a lot slower without the leaking cap on the older style tank. With the older one I flew from Austin to Tampa and no light, despite the tank being quite low.

Re: DA62 coolant leaks

Posted: Thu Jun 14, 2018 1:38 am
by CFIDave
Interesting that you just mentioned this issue.

Last week for the first time (my DA62 is now one year old) I got a Low Coolant Lvl annunciation for the right engine immediately at startup. But after about 5 minutes of warming up the engines on the ground, the annunciation goes away, and it never shows up again during the flight or after landing. It now does this every time the engine is cold -- I don't even need to start the engine to see the low coolant annunciation, just turn on the Electric Master to boot up the G1000.

So before my last trip, I removed the engine cowlings to check the coolant level inside of the expansion tank on top of the right engine. After cutting the safety wire and unscrewing the expansion tank "radiator cap," I got surprised by the blue coolant shooting out under high pressure! (This with a totally cold engine that hadn't been started for days.) There's no way you could add any new coolant to top off the system, since the level is still all the way to the top of the opening. And before I did this, I could find no evidence of any leakage.

So I cleaned up the mess, screwed the cap back on, applied new safety wire, put the cowlings back on and went flying. I still get a Low Coolant Level annunciation that goes away after the engine warms up on the ground before takeoff. When flying, coolant temps are within 1 degree of each other on the left and right engines.

I never had a problem like this in 4 years of flying a DA42-VI also with Austro engines. I guess it's time to contact Diamond in London to figure out why I'm getting the temporary Low Coolant Level annunciation.

Re: DA62 coolant leaks

Posted: Thu Jun 14, 2018 6:57 am
by Antoine
Just my 2cts from another water cooled engine operator.
The coolant circuit becomes pressurized when the engine is warm and it should not leak this pressure. This is the explanation of Dave's experience.

Pressure is critical to keeping the boiling point of the coolant higher. The higher you fly the greater the pressure differential between your circuit and the outside atmosphere - so the more likely it is to leak if anything is not ok.
Therefore, even a leak in the coolant circuit that only releases pressure without releasing liquid (for example if it happens at the level of the relief valve which would be above coolant level) is potentially nasty.
You do NOT want your coolant boiling.
When testing on the ground, it is necessary to overpressure the circuit to detect leaks that seem to only happen in flight when ambient air pressure is low. It is 0.5 atmosphere at FL180.

Re: DA62 coolant leaks

Posted: Thu Jun 14, 2018 1:31 pm
by DA62
Hello All
Before my 200hr/Annual in May I got the "low coolant annunciation" on the right engine before 3 flights. It went off as soon as engine got warm. I told Glen at Southtec what happened and when they removed the cap to check the fluid level it was pressurized and blew fluid out. They topped it off and I have flown close to 25hrs since and it has not happened again. I never had any fluid leaking. Glen is aware so you might call and ask him.

Mike

Re: DA62 coolant leaks

Posted: Wed Oct 24, 2018 1:34 am
by neema
Sort of a thread resurrection, but we're in a similar boat with the "low coolant lvl" annunciator when engines cold--goes away after 3-4 minutes on our 42-VI. Added a little coolant to the reservoir and haven't had it come back, but we definitely didn't have any coolant blow out.

Re: DA62 coolant leaks

Posted: Wed Oct 24, 2018 1:07 pm
by CFIDave
After the experience I described above, I opened up the coolant reservoir a 2nd time (it didn't blow out under pressure this time) and noticed that the level was actually low. I topped it off with a very small amount of distilled water and no longer receive any Low Coolant Level annunciations.

Re: DA62 coolant leaks

Posted: Sun Nov 17, 2019 1:13 am
by phillipb115
I know its been a while since this thread was active but I recently got a contract flying a DA62 and also have noticed the persistent low coolant caution light when the engines are cold and then goes away after things start to warm up. Nothing seems to be leaking. Could this just be a common sensor issue?

Re: DA62 coolant leaks

Posted: Sun Nov 17, 2019 1:16 pm
by ememic99
phillipb115 wrote: Sun Nov 17, 2019 1:13 am I know its been a while since this thread was active but I recently got a contract flying a DA62 and also have noticed the persistent low coolant caution light when the engines are cold and then goes away after things start to warm up. Nothing seems to be leaking. Could this just be a common sensor issue?
I had same problem with DA42 and it turned out it was a very small leak.