DA62 coolant leaks

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jb642DA
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Re: DA62 coolant leaks

Post by jb642DA »

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?
We have 170 hours on ours.

Temps anywhere from -20 F outside air temp. (Coolant temp at start was -5C / +22F. Fortunately, it was in hangar until an hour before start.) to 95 deg F. Never any coolant caution lights.
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Re: DA62 coolant leaks

Post by CFIDave »

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've had the same thing recently happen again on my right engine, so I removed the cowling. It looked like the coolant overflow valve had opened up and sprayed a small amount of blue coolant over the top of the engine. So when the engine was totally cold I cut the safety wire and slowly opened up the cap -- slowly releasing the pressure -- and discovered that the coolant level was all the way to the top and way ABOVE the "coolant level" mark inside the coolant reservoir. There was simply no way to add any more coolant. So I put the cap back on, sealed with new safety wire, and went flying. Since then the PFD low coolant level annunciation occasionally comes on with a cold engine, but it quickly goes away as the engine warms up before takeoff.

I'm wondering if there may be some air bubbles somewhere in the system that may work themselves out; I may open the cap again to see if it's possible to add more coolant, but I find this to be very strange behavior.
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Re: DA62 coolant leaks

Post by cflake »

I purchased a Diamond DA42 VI approximately 2 months ago (2016 w/ 300 hours) pre-buy inspection conducted at Diamond facility in Canada - shortly after taking delivery - I started to experience a coolant leak on the right engine in flight (blue fluid coming through the seams over the cowling) - unfortunately - after 2 visits to a Diamond repair center the problem persist. The plane is back in the repair shop (It's spent more time there than any other place in my 2 months of ownership) and they believe they found the issue to be a reservoir and cap. They said Diamond made an "upgraded" version of this - so it is on order and we will see how this goes. Fortunately - much more serious items like head gasket and cracked block were ruled out.

As a new owner of a Diamond Aircraft which cost as much a nice used jet - it's been very concerning to have these problems so quickly... Most of my missions take me over water or mountains and I feel like I shouldn't go more than 50 miles from my repair facility... Hopefully things will get better soon.
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Re: DA62 coolant leaks

Post by ultraturtle »

One thing that sucks a little bit about fantastically automated aircraft is that they tend to fantastically report every little problem. My coolant level indication problem (on one engine only) subsides after five minutes or so of engine warm up, so I’ll not worry much about it till my next annual

The bunch of us on this forum that have gone through the Diamond Austro engine maintenance education program have seen a video that demonstrates that the mechanic needs to knead the coolant hoses carefully and constantly while being filled during recurrent maintenance in order to eliminate air gaps. The vacuum fill video (which would totally eliminate this issue) was mind blowing, but sadly is only available at the manufacturer facility..
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Re: DA62 coolant leaks

Post by Davestation »

Perhaps I read too fast but I didn't see anyone describe what is clearly happening when the alert goes out - the cold coolant level was low, and as it warmed up and expanded, it rose to above the low trigger. The tank is quite small and it doesn't take much for the level to fluctuate. Complacency has lead to the practice, for some who see this alert often, to just wait until the alert goes away to take off. The engine could easily lose a quart of coolant before it even makes it to the ground for the pilot to discover, however.

Agreed the placement of the relief valve is poor. These valves are known to get gummed up and leak - in which case they just need to be cleaned and reinstalled. I did find several that suffered infant mortality though and were simply opening at way too low of a pressure, so naturally the coolant would always leak out and be low. I wish they would at least plumb the valve to the bottom of the cowling like the old caps were so that it doesn't make a mess of the engine compartment and you could actually see it dripping out without removing the cowling. I don't remember the issue of the low coolant ever returning after replacing the relief valve with a brand new one.

As for the low indication when the tank is actually full, this seems to be a common gremlin. For starters, if you upgrade your tank, you need to upgrade the sensor too or the old slightly larger one will get stuck. What I couldn't seem to figure out is if even the new sensors were intermittently getting stuck until the engine warmed up and broke them loose or what. One theory is that it is a software sensitivity issue (seems to plague the 62 a lot more than the 42NG). I don't remember the issue of the annunciator ever returning after replacing the sensor though, perhaps a stronger magnet is all that is required.

I am not a fan of the new tanks though, so I wouldn't "upgrade" unless the old one is cracked (I've seen them crack at the filler neck weld and leak from there but only on very high time applications or perhaps after they were manhandled). The old caps are simple and effective. The new caps tend to develop a leak overtime in which case you have to reapply the EZ Turn, and there's really no right way to do it (in that it's a huge mess).
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Re: DA62 coolant leaks

Post by juanla@aol.com »

The low level coolant anunciador come on and after reading this treads I thought it was a glitch. However after the 4 flight the right engine finally got hot. After putting water 2 times we finally found out that the pressure relief valve is at fault. Called Dave at Premier an he said is a persistent problem with the DA 62. I have the part on order….what a pain.
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Re: DA62 coolant leaks

Post by CFIDave »

Yes, there's currently a 6-8 week wait for a new coolant tank pressure relief valve. Get in line...

But I've been told (by SouthTec owner Glenn Lawler) that all that may be needed is a good cleaning of the valve. Apparently whenever overflow occurs, it creates a buildup of dried blue coolant on the relief valve that causes it to open prematurely. (Of course this doesn't explain why the valve opened prematurely the first time -- which is why I have a new valve on order for my right engine.)

I was told by the Canada factory that Diamond/Austro is very aware of this issue, and is working on a fix.
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Re: DA62 coolant leaks

Post by VickersPilot »

Was a fix released in the end for this issue?
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Re: DA62 coolant leaks

Post by CFIDave »

VickersPilot wrote: Sat Apr 22, 2023 6:59 pm Was a fix released in the end for this issue?
I sold my DA62 last November, but the fix for low coolant level (and occasional opening of the valve, spraying coolant on the engine) was replacement of the overflow valve with a new one -- the issue went away completely.
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Re: DA62 coolant leaks

Post by photoSteveZ »

My ‘old’ 2018 DA62 had coolant release issues even after replacing the overflow valve on the offending engine. My ‘new’ 2022 DA62 hasn’t suffered a single coolant release in its first 170 hours.
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