Coolant leakage

[Deanrobert]

We have slight, but consistent coolant staining on the block of our engines, that we see when we check the oil , on both sides. Service center suggesting replacing pressure relief valves.. just curious if any of you have experienced this
Plane has 435 tt on it 2017 model …

[Boatguy]

My mechanic mentioned this as a problem in DA62's. I would pursue this with Diamond / Austro before paying your shop to "replace and pray".

[vnehess]

The pressure relief valve can be tested by inserting a simple "T" into a cooling line and applying compressed air until the valve pops, then reading the pressure to determine if the valve releases at the specified value (~29-33 psi if I recall). This was done on my 2019 40NG to help isolate an issue with coolant loss.

[Deanrobert]

Thanks, I’ll do that

[Deanrobert]

The pressure relief valve can be tested by inserting a simple "T" into a cooling line and applying compressed air until the valve pops, then reading the pressure to determine if the valve releases at the specified value (~29-33 psi if I recall). This was done on my 2019 40NG to help isolate an issue with coolant loss.

What was the final determination on your coolant loss ?

[vnehess]

summary;
installed new head, appears resolved.

theory:
pressurized gasses from intake or compression were leaking into the sealed coolant system.

details;
DA40NG 2019, found consistent elevated pressure in the coolant system after long flights.
3 hour flights would yield observable coolant loss.
3 hour flights would yield 16+ psi (in the coolant system) remaining after the engine cooled off.
no overheating observed on any flight.
after consulting with Diamond/Astro, decided to remove/inspect intake manifold.
after inspection & consultation with Diamond, replace head (new part #).
work resolved within warrantee period, priceless.

status:
All flights after repair, no observed coolant loss.
Need additional longer flights to confirm initial reports of successful repair.

[VickersPilot]

Cylinder Head?

[vnehess]

Yes, replacing the Cylinder Head resolved the problem (head gasket leak).
The diagnosis was done with two observations, coolant loss and pressurized coolant system after long flights.
I'm back in the air now and conducting longer flights as weather permits (VFR pilot)

I am very happy with the mechanics at Alpine Aviation for diagnosing the issue and the support from the Diamond team to resolve.

[CFIDave]

Questions for anyone having this issue with an Austro engine:

1. Was your coolant loss only through the overpressure relief valve on top of the engine, or coming from elsewhere (e.g., stains from head gasket area)?

2. After flying and observing coolant loss, did you also see a low coolant level annunciation on your G1000?

3. Did your coolant loss occur in flight, or only on the ground after (hot) engine shut-down?

[vnehess]

My case was loss thru the relief valve.
Low coolant announce was observed on the next flight.
Loss appears to be in-flight but I did not see the fluid until later when it had drained down to lowest point and dripped out. No visible indication of loss while flying, no high temp condition, initial discovery was next morning after long flights.