(Slight) Radiator Leak

[Amadeus]

RV-12iS
Almost two years flying
194.3 hours
Coolant temperature is always in the green even in extended climb

Over the past few months I have noticed trace amounts of water on the floor of the hangar near the nose gear. In Kentucky, in the winter and spring, water is not out of place. I find water at all three wheel pant locations from precipitation the tires throw inside them to drain out later in the hangar. But sometimes it is only the nose gear and given that coolant leaking from the radiator drips into the lower cowling before then running down the nose gear leg into the wheel pant before dripping onto the floor it is always dirty brown water.

However it is Annual Condition Inspection time again (woo-hoo, second one) and the cowling has been off for more than a week. I arrived at the hangar this morning to find a very small puddle of orange water indicating coolant. I checked the radiator and found a small bead of water along the lower radiator frame at the bottom of the fins. I used compressed air to blow through the fins and it did blow out more coolant. Checking again a couple hours later and found a smaller bead of water along the bottom of the fins again.

Could I remove the coolant line that goes from just under the "radiator cap" to the overflow bottle and apply air pressure through that opening (and how much? 20#? 30#?) to be able to push coolant out and identify just where the leak is occurring and assess whether applying Marine-Tex is an option?

Is it possible (or even advisable) to take the radiator to a local automotive radiator repair shop to get this fixed?

This is a two year old low hour Rotax 912iS - why would the radiator fail so quickly?

[Bob Y]

Your post is unbelievable - because I just had the same issue, except more dramatic! I ended up AOG about 90 miles from my home base due to my radiator leak at what you describe as the same location? It completely emptied the radiator and apparently happened upon landing, as check the data log showed NO sign of increased coolant temperature. In my case, 285 hours and over 300 landings. I assume it was that last shock on landing that finally caused it to give up.

If you look at the attached photos, it appears there’s a gouge in the BACK of the radiator. I used soapy water with pressure to find the leak. I expected to see something like that on the front from FOD that may have punctured it, but on the back? I assume it was either damaged in shipment and I never noticed it, or I damaged it on installation. I told my friends it had to be the former as I couldn’t have possibly done it 🙂.

Anyway, I’d be curious to know if your leak is in the same location as mine and if you see a similar gouge. And I doubted repair was possible so had to spend +$800 for a replacement p, tax & freight included.

[Reilly]

I have had this happen twice. Not a Rotax engine.
First time I took the radiator off and took it to a radiator shop for a pressure test. Had a leak in top left corner where the tubes go through the side wall. You can't weld there and it could only be fixed with an epoxy.

I was not happy with this fix in an aircraft so had a new one custom made. This time fitted with rubber mounts as the first one had none.

50 hours later had the same issue in a different place so now fitted my 3rd.

I discovered my rubber mounts were way too hard so fitted softer ones. I also discovered that my 2 second shudder after each takeoff was due to an out of round and unbalanced nose wheel. This could well have contributed.

So I believe in my case a stiff mounting not able to absorb vibration and stresses may have been the cause.

The way I understand it is the the core goes through a special process to seal the sides to the tubes. The tanks are then welded on the sides. There is always a chance that in welding the tanks that the side seal to the tubes gets weakened or damaged that later leaks.

My advice is to pressure test and if leaking from the core then replace and try to make it as vibration and shock resistant as possible.

Hope this helps.

[bobg56]

There's an old service letter regarding the need to trim were the radiator contacts structure, a clearance dimension is given, mine developed a pin hole leak. I removed the radiator, flushed it out, cleaned area with alcohol and used a small bit of Marine Tex Epoxy. Created required clearance. No more leaks at over 200 hours. Or you can spend about $500 for a new radiator.

[TS Flightlines]

Not that it means anything, but back in my automotive days, we found that Dexcool, the orange antifreeze, would deteriorate some aluminum heater cores and radiators from a certain automotive manufactor. Dont know who the vendor was that was supply the radiators and heater cores but the chemicals in the Dexcool was eating the aluminum.
Potentially something similar here.

Tom

[WJaviation]

Had the exact same thing happen to my radiator at about 200hrs as well.

Mine was separating from the radiator frame on the lower portside frame connection, where the fins connected to the frame. It looked like it had bubbled up the black paint and then started leaking. Dribbling down the inner cowling and on to the floor.

Ended up buying a new one from Vans for $800+. This was exceptionally painful considering that I was able to locate the supplier and they only wanted $250 for a brand new radiator! Quite the mark up!

[Amadeus]

Originally Posted by Bob Y

If you look at the attached photos, it appears there’s a gouge in the BACK of the radiator.

Originally Posted by WJaviation

It looked like it had bubbled up the black paint and then started leaking.

This is the odd part; the radiator does not have a gouge, bubbled up paint nor even a fin that isn't uniform. It looks brand new!

Sorta points to Tom's orange antifreeze affecting the aluminum parts theory...

[mikefox]

What RPM for idle are the folks here who have a leaky radiator using?

And was the prop balanced or mot?

[Amadeus]

Originally Posted by mikefox

What RPM for idle are the folks here who have a leaky radiator using?

And was the prop balanced or mot?

Prop balanced.

Idle at 2200-2300 RPM. Only time engine runs below 2200 is at flare on landing and briefly after during clean-up before getting back above 2000 for taxi.

[BillL]

Originally Posted by TS Flightlines

Not that it means anything, but back in my automotive days, we found that Dexcool, the orange antifreeze, would deteriorate some aluminum heater cores and radiators from a certain automotive manufactor. Dont know who the vendor was that was supply the radiators and heater cores but the chemicals in the Dexcool was eating the aluminum.
Potentially something similar here.

Tom

The original supplier was Chevron - Havoline brand OAT extended long life coolant. After 5+ yrs it will become acidic and eat aluminum. I just replaced my $700 radiator in my classic M5 for this reason. [shame on me, I knew better - what I did not know is the car value would increase by 10X while stored]

Originally Posted by Amadeus

This is the odd part; the radiator does not have a gouge, bubbled up paint nor even a fin that isn't uniform. It looks brand new!

Sorta points to Tom's orange antifreeze affecting the aluminum parts theory...

Jayson, your bird is not old enough, it is not internal coolant corrosion- you have a mechanical failure of the aluminum from over stress. Vibration is a killer of heat exchangers. I would consult Vans first, to obtain the latest recommendations. If you get the "we have never heard of that" response, then press them for a design solution for softer mounts, installation force causes and if a cross brace is needed to keep the unit from racking. Any operational regime that feels smoother is better.

OAT is organic acid technology and was a breakthrough for extending life of coolant when released in the industry, the downsides were found after GM released to the field w/o long term testing.