Leaking radiator troubles - RV-12iS

[fehdxl]

Hi folks,

Is your RV-12iS radiator leaking? A little? A lot? Or totally dry?

We’ve been having an on-going issue with multiple radiators that’s pretty frustrating… just trying to see what’s going on with the rest of the community and see what fixes have been done and such.

Thanks. Fly safe!

-Jim

 

[Bob Y]

Just this past April I was AOG about 100 miles from home due to a severe leak in mine. Had to order a rush replacement. Couldn’t see the leak until removing it. The leak was from a gouge on the INSIDE of the engine compartment. So, either it was damaged during shipment and I didn’t notice it, or I did during installation. But it held for almost 300 hrs before finally leaking. And since the gouge was at the bottom of the radiator, it naturally completely drained it. I wasn’t about to trust a repair, but again didn’t know where it was anyway until replacing it.

 

[rcarsey]

I discovered a tiny leak on my pre-flight to Oshkosh this year. It was such a small amount, I couldn't be sure if it was condensation or antifreeze. It felt a little slippery like antifreeze, but it wasn't enough to be sure. I launched anyway.. figuring this leak had probably existed for many hours previously ..but was simply undiscovered until now. I was checking the fluid levels at each stop though - I didn't find a cause for grounding or to turn back. I did note that my coolant reserve level was 1/8" low at the last annual -- but I chalked it up to internal leaks, evaporation, etc.

I ordered a replacement this weekend with 2-day shipping. Since OSH, the leak is more apparent.. so I'm under self-imposed grounding for now -- though I'd feel comfortable flying within a 5-10 minute radius of an airport now (pattern work).

I think this radiator issue is starting to come up to a level that may warrant factory investigation. I have 490 hours and am still on the original fill of Prestone Extended Life DEXCOOL 50/50 pre-mix (as recommended by Rotax SI-912i-001R8). There've been many others with radiator leaks so far:

1. aobrien5
2. WJaviation
3. Giving_Wings
4. mikefox
5. bobg56
6. Amadeus
7. Bob Y
8. Reilly (twice)

The photo is showing the lowermost cooling fin row, forward facing side, about 2 inches from the copilot-side edge of the fins

 

[Amadeus]

The photo is showing the lowermost cooling fin row, forward facing side, about 2 inches from the copilot-side edge of the fins

My leak was(is) occurring at the exact same location as yours and looks exactly as your photo depicts. I drained the radiator, cleaned the area, allowed to dry a couple days then used a syringe to push Marine-Tex into the fins. The leak is *mostly* gone. I find a drop occasionally on the bottom ledge in front of the fins. Cooling is normal in flight.

 

[fehdxl]

Please add me to the list as we’re now at radiator leak x4!!! …or maybe it’s 5… lost track.

We also have 1,200+ hours on our engine in 2-1/2 years…

-Jim

I think this radiator issue is starting to come up to a level that may warrant factory investigation. I have 490 hours and am still on the original fill of Prestone Extended Life DEXCOOL 50/50 pre-mix (as recommended by Rotax SI-912i-001R8). There've been many others with radiator leaks so far:

1. aobrien5
2. WJaviation
3. Giving_Wings
4. mikefox
5. bobg56
6. Amadeus
7. Bob Y
8. Reilly (twice)

The photo is showing the lowermost cooling fin row, forward facing side, about 2 inches from the copilot-side edge of the fins

 

[Amadeus]

We also have 1,200+ hours on our engine in 2-1/2 years…

Over 500 hours per year. Impressive use of an RV! That's at least 24 oil changes - you must be performing maintenance every other week.

My leak was discovered when total time was under 200 hours. I now have 230 hours in 2 years, 1 month of flying. I need to step up my game to keep up with Jim!

Given fehdxl experience it appears that the radiator on the -12 has a 200 hour useful life. Is there a viable alternative to continuing to purchase an $800 radiator every 200 hours?

 

[Piper J3]

Just to add a data point…. I have 850TT on my RV-12 ULS. It is a very early SN that was christened in 2013. Original coolant radiator has no leaks. I changed to Silicone High Temp coolant hoses when I did 5-year rubber replacement. The silicone is very soft and imparts much less stress/vibration to the radiator coolant tanks. Or, maybe they just made better radiators back-in-the-day…

Having said that…. I do have a small persistent leak from the weep hole on the water pump. I have been monitoring coolant level for several years and the leak has not progressed…

 

[WJaviation]

I discovered a tiny leak on my pre-flight to Oshkosh this year. It was such a small amount, I couldn't be sure if it was condensation or antifreeze. It felt a little slippery like antifreeze, but it wasn't enough to be sure. I launched anyway.. figuring this leak had probably existed for many hours previously ..but was simply undiscovered until now. I was checking the fluid levels at each stop though - I didn't find a cause for grounding or to turn back. I did note that my coolant reserve level was 1/8" low at the last annual -- but I chalked it up to internal leaks, evaporation, etc.

I ordered a replacement this weekend with 2-day shipping. Since OSH, the leak is more apparent.. so I'm under self-imposed grounding for now -- though I'd feel comfortable flying within a 5-10 minute radius of an airport now (pattern work).

I think this radiator issue is starting to come up to a level that may warrant factory investigation. I have 490 hours and am still on the original fill of Prestone Extended Life DEXCOOL 50/50 pre-mix (as recommended by Rotax SI-912i-001R8). There've been many others with radiator leaks so far:

1. aobrien5
2. WJaviation
3. Giving_Wings
4. mikefox
5. bobg56
6. Amadeus
7. Bob Y
8. Reilly (twice)

The photo is showing the lowermost cooling fin row, forward facing side, about 2 inches from the copilot-side edge of the fins

Yep I had 200hrs on my radiator when I developed the same leaks in the same position as Rcarsey. I actually made contact with the original builders/fabricators of the radiators. An outfit by the name of http://www.aluminiumracing.com/ in Czech Republic.
I tried to order directly from them for much cheaper than what Vans offered, but eventually the lead guy ghosted me on email. My guess is vans told them to cease and desist so that builders had to buy through Vans instead of direct from supplier.

There have got to be other off the shelf aftermarket radiators that meet the specs and also could be fabbed by a local aluminum welding shop to fit our attach brackets.

 

[Amadeus]

I have sent a custom radiator build request to Ron Davis Racing Components to see if they could produce something for the RV-12iS application. I mentioned that 8 to 10 would be needed initially and if they proved to last longer than just 200 hours of flight time then they should approach Van's about becoming a supplier! The radiators we're getting are not quality products.

 

[seagull]

I have a RV-12ULS first flown in 2015, It has 1245 hrs and no coolant leaks. It appears most if not all of these radiator leaks are -12iS related. The -12iS mounts the coolant radiator to the engine on the front. The -12ULS instead mounts it on the left side to the firewall with airflow connected by the cowl duct. This front engine mounted position may be picking up an engine vibration and or prop air pulses.

My 2 cents, just thinking out loud.

 

[rcarsey]

Can anyone with a failed -12iS radiator please state what coolant you were using?

While I doubt this contributes to the cause, it might be worth eliminating as a factor.

 

[Piper J3]

1. aobrien5
2. WJaviation
3. Giving_Wings
4. mikefox
5. bobg56
6. Amadeus
7. Bob Y
8. Reilly (twice)

I'd bet vibration or stiff hose. Oh geez... I can't believe I said that....

 

[fehdxl]

Over 500 hours per year. Impressive use of an RV! That's at least 24 oil changes - you must be performing maintenance every other week.

Youth built project. Now 10 of us own it. Used for personal training and time building… light sport, private, instrument, commercial, cfi and instrument cfi checkrides all taken in our -12.

This month was slow with only 45 hours… usually we are doing oil changes once a month.

It is a lot, but it’s a great machine… sans the frustrating radiator leak.

 

[Amadeus]

Can anyone with a failed -12iS radiator please state what coolant you were using?

Orange. DexCool.

 

[Bob Y]

Zerex G48 50:50

 

[rvbuilder2002]

I wasn’t aware that there had been so many similar leaks occurring in the radiators.
The best way to get some attention on this from vans is to use the service difficulty reporting process that is detailed in the RV 12 maintenance manual.

 

[fehdxl]

I'd bet vibration or stiff hose. Oh geez... I can't believe I said that....

Would you suspect:

(1) the higher frequency vibration during long periods of operating time; or

(2) the larger and possibly harder low frequency vibration during the engine start and shutdown?

I kind of think 1, but just a guess.

-Jim

 

[Piper J3]

Would you suspect:

(1) the higher frequency vibration during long periods of operating time; or

(2) the larger and possibly harder low frequency vibration during the engine start and shutdown?

I kind of thing 1, but just a guess.

-Jim

Difficult to say... harmonic frequencies come into play.... all kinds of stuff. Best practice is to isolate the radiator mounting - soft mounts and soft hose at connections. And, not have radiator mounted on engine...

 

[mikefox]

Our club uses dex cool 50/50 premix for the radiator.

And we increased the idle speed to 1800 rpm.

We’re on our second radiator at 953 hours.

 

[mrpilotron]

I am one of the other co-owners of Jim's plane. One thing I tried to do last time we replaced the radiator was eliminate as much binding and pre-load stress as possible. The original holes and brackets aligned so poorly that forcing them into position would have created a lot of torque on the lower fin mounts right where the leaks tend to happen. I filed and sanded for quite some time to relieve the interferences and make sure the radiator sat very gently into position prior to snugging the bolts. I thought I had fixed the root problem, but here we are again after another ~250 hours watching the thing leak again. The good news is that this time it's just a slight weep (so far) that only looses about 1 ounce of coolant in 4 to 5 hours of flight. The previous failure was enough to immediately ground the plane.

I am not a fan of mounting that radiator so tightly with those thin rubber washers that do almost nothing to absorb harmonic vibrations. I would love to see Van's redesign that mount to allow it to float around by 1/8 inch or so just to make sure that it isn't subject to material fatigue between the bottom cooler row and the lower support bracket.

 

[WJaviation]

I am one of the other co-owners of Jim's plane. One thing I tried to do last time we replaced the radiator was eliminate as much binding and pre-load stress as possible. The original holes and brackets aligned so poorly that forcing them into position would have created a lot of torque on the lower fin mounts right where the leaks tend to happen. I filed and sanded for quite some time to relieve the interferences and make sure the radiator sat very gently into position prior to snugging the bolts. I thought I had fixed the root problem, but here we are again after another ~250 hours watching the thing leak again. The good news is that this time it's just a slight weep (so far) that only looses about 1 ounce of coolant in 4 to 5 hours of flight. The previous failure was enough to immediately ground the plane.

I am not a fan of mounting that radiator so tightly with those thin rubber washers that do almost nothing to absorb harmonic vibrations. I would love to see Van's redesign that mount to allow it to float around by 1/8 inch or so just to make sure that it isn't subject to material fatigue between the bottom cooler row and the lower support bracket.

I've got my old radiator still. I wonder if we mailed the old leaking ones into Vans for inspection they'd have some more concrete measurable evidence of the problem. I intended to have mine repaired at a local shop but never did.

 

[fehdxl]

I've got my old radiator still. I wonder if we mailed the old leaking ones into Vans for inspection they'd have some more concrete measurable evidence of the problem. I intended to have mine repaired at a local shop but never did.

Van’s has number one and two of our leaking one’s already. Currently we have number three and four in our hangar. The number five is on the plane now. :-(

 

[fehdxl]

Leaking Radiator Feedback Form

To help Van’s understand the issue, please send a Feedback Form (attached) to engineering -at- vansaircraft.com.

 

[rcarsey]

Sounds like they're aware of the issue already. I did submit that form.. along with photos of the leak location, and a list names and/or serial #s of other leaks I found here on VAF.

I did mention that it could be beneficial to look through their part orders to find anyone who ordered an "extra" radiator.. its not a part that a builder would mess up during construction .. so a purchase likely means they had a leak.. hopefully they can collect more info from those purchasers.

They're probably stretched thin with the ongoing RV-15, laser-cut hole debacle, and other things.. the last thing they need now is more work.. but it is what it is. At least this time around, I was more careful not to introduce any extra stresses to it while mounting.

 

[Amadeus]

To help Van’s understand the issue, please send a Feedback Form to engineering -at- vansaircraft.com.

Submitted mine:

 

[mrpilotron]

I pulled out one of our failed radiators (#3) and devised a little pressure testing rig to pinpoint exactly where the leak is happening.
https://vansairforce.net/community/attachment.php?attachmentid=46342&stc=1&d=1691760868

This one ended up being on the pilot side, facing the engine, right at the outer most point of the cooling tube where it has the tightest radius of the oval shape. Even knowing exactly where the leak is, I can't see a hole there when it's dry so visual inspection is pointless without a way to make bubbles.
https://vansairforce.net/community/attachment.php?attachmentid=46341&stc=1&d=1691760868

I was a bit surprised that the failure point is on the engine side. We always saw the fluid coming out the front while the back was just barely damp so we assumed the barely damp part was due to air flow pushing it back. No true.

I also discovered a spot at the top of the radiator where I initially thought it might be a leak spot, but it turns out there is no fluid behind this area and this slight blemish is of absolutely no consequence. (The photo is upside down. Don't let the orientation fool you.)
https://vansairforce.net/community/attachment.php?attachmentid=46340&stc=1&d=1691760868

 

[Godo]

Running out of cooling fluid

Hi, I just wanted to share my experience with a leaking radiator.

Around 450h I started noticing few drops of cooling liquid on the floor, that I kept refilling in the center reservoire.

Besides those few anoying drops, nothing else noticed.

At 500h in a local flight I noticed the cooling liquid coming into the cabin throught the cabin heating holes, followed by a sudden increase (less that 1 min) of the temp beyond 130-140°C (266-284°F) and a warnings on the Dynon all over.

Fortunately I was near an airport and could glide in less than 5 mins (engine on, windmilling).

The Rotax mechanic told me that, should I have stayed over 280°F longer than 6 or 7 min, the engine would have had to go for serious checks...

My take on this one: Do not procrastinate and just refill. That mini crack may develop in the most inconvenient momment leaving you to a forced landing.

Godo

 

[mrpilotron]

I just finished installing radiator #5 in the plane that started this thread. I attempted a repair on #3 with epoxy smeared over the leaking area. That didn't work. I suspect I didn't go deep enough into the fins to cover the whole area that was damaged. So, now we have #3 with a mess of epoxy and still leaking, #4 removed due to leaking and showing the same damage pattern in the same location, and #5 freshly unwrapped from shipping and working nicely. It's nice to have no leak, but I just know it's only a matter of time before we'll be replacing this one too.

I noticed when I was dabbing epoxy into #3 with a toothpick that the little fins moved around a little due to the brazed connection with the coolant tubes failing. I suspect that the braze pulled a hole in the sidewall of those little thin coolant tubes due to the stresses that get transferred into the framework of the radiator. #4 has the same disconnected fins in the same location where the leaking happens.

After carefully examining how the radiator mounts to the top of the oil coooler, I have a new working theory about why this failure is happening. I may be completely wrong, but here goes: The top of the oil cooler bolts solidly to the bottom of the radiator. The top of the oil cooler also mounts with squishy rubber mounts to the engine. The bottom of the oil cooler is left swinging in the breeze except for a couple of oil lines that might provide a marginal amount of support. The top of the radiator mounts to the engine with some similar squishy rubber mounts. The whole solid assembly of radiator and oil cooler is therefore supported by 4 rubber mounts, 2 at the top and 2 in the middle where the radiator and oil cooler connect. Every time the prop swings by, a brief pulse of wind blasts through the cooler stack. These prop pulses set up a rythmic fore/aft cycling force that is absorbed by that oil cooler swinging in the breeze and causing the rigid joint between the oil cooler and radiator to be a hinge point pushing on the engine mount. After hundreds of thousands of these pulsing fore/aft impacts, the slight flex absorbed by the bottom row of fins in the radiator eventually causes metal fatique in the coolant tube and the braze pulls out of the tube causing a leak.

I would love to take a very fine saw and pre-emptively cut through the fins in that area to allow the frame to flex ever so slightly without pressing on the lowest coolant tube. Do I dare try that on our brand new #5 radiator? I can't afford to keep buying $800 radiators every 200 hours.

 

[mrpilotron]

One additional thing I'd like to add for the benefit of anyone else dealing with this: Ground the plane if it's leaking! We didn't on the assumption that we could keep an eye on the plastic reservoir and monitor the loss rate that way. It turns out that this gives a false sense of how much fluid is actually lost. The little expansion chamber (AKA: middle reservoir) on top of the engine was almost completely empty while the plastic reservoir on the firewall was still 80% full. No harm done this time, but it really bothers me that we were dangerously wrong about how much coolant was in the system due to the reservoir showing plenty of coolant when that wasn't the case.

 

[KEG]

Just curious... Has anyone received a response from Van's regarding this issue? I am nearing the point of hanging the radiator on my new build 12iS.

 

[Amadeus]

Just curious... Has anyone received a response from Van's regarding this issue?

Yes. A note from the engineering department:

"Thanks for the feedback. We are now collecting information on this issue. I have sent an email back to the manufacturer asking questions.

Where exactly was the leak coming from? Front or back side? In front of the bracket / lug that connects the oil cooler (this has been the case in a couple of these)?

We will get back to you as we learn more about this issue."

I replied with answers from my experience. Hope they can find a solution.

 

[rcarsey]

Just curious... Has anyone received a response from Van's regarding this issue? I am nearing the point of hanging the radiator on my new build 12iS.

Yes. I heard from Rian himself in response to me report to engineering@vans. To paraphrase what was said.. They are collecting data.. they're in contact with the mfg to see if the cooler can be improved. The overall percentage of failures is low (though personally, I'm unsure how many -12iS's already have 400+ hours logged already). May need a redesign of the oil cooler support.. trying to determine if that bracket is causing a stress concentration locally and "if so, I may have a solution". Also could be linked to installations with a rougher engine/prop combination.

So, I'd encourage others to submit reports to engineering, even if you've had a failure in the past.. including as many details as possible.. which prop option you have, hours at failure, exact location of leak found, etc. More details are better than too few.

 

[rvbuilder2002]

I just finished installing radiator #5 in the plane that started this thread. I attempted a repair on #3 with epoxy smeared over the leaking area. That didn't work. I suspect I didn't go deep enough into the fins to cover the whole area that was damaged. So, now we have #3 with a mess of epoxy and still leaking, #4 removed due to leaking and showing the same damage pattern in the same location, and #5 freshly unwrapped from shipping and working nicely. It's nice to have no leak, but I just know it's only a matter of time before we'll be replacing this one too.

I noticed when I was dabbing epoxy into #3 with a toothpick that the little fins moved around a little due to the brazed connection with the coolant tubes failing. I suspect that the braze pulled a hole in the sidewall of those little thin coolant tubes due to the stresses that get transferred into the framework of the radiator. #4 has the same disconnected fins in the same location where the leaking happens.

After carefully examining how the radiator mounts to the top of the oil coooler, I have a new working theory about why this failure is happening. I may be completely wrong, but here goes: The top of the oil cooler bolts solidly to the bottom of the radiator. The top of the oil cooler also mounts with squishy rubber mounts to the engine. The bottom of the oil cooler is left swinging in the breeze except for a couple of oil lines that might provide a marginal amount of support. The top of the radiator mounts to the engine with some similar squishy rubber mounts. The whole solid assembly of radiator and oil cooler is therefore supported by 4 rubber mounts, 2 at the top and 2 in the middle where the radiator and oil cooler connect. Every time the prop swings by, a brief pulse of wind blasts through the cooler stack. These prop pulses set up a rythmic fore/aft cycling force that is absorbed by that oil cooler swinging in the breeze and causing the rigid joint between the oil cooler and radiator to be a hinge point pushing on the engine mount. After hundreds of thousands of these pulsing fore/aft impacts, the slight flex absorbed by the bottom row of fins in the radiator eventually causes metal fatique in the coolant tube and the braze pulls out of the tube causing a leak.

I would love to take a very fine saw and pre-emptively cut through the fins in that area to allow the frame to flex ever so slightly without pressing on the lowest coolant tube. Do I dare try that on our brand new #5 radiator? I can't afford to keep buying $800 radiators every 200 hours.

I could be wrong but I am highly doubtful that there is anything dynamically causing this, as related to specifics regarding the cooling system design
The reason for my skepticism is the same as I have mentioned often in the past…. Data.
There are lots of earlier build RV-12’s with lots of flight hrs, that are still flying with their original radiator.
I think it is more likely some variable in the manufacturing process but we will have to wait and see what the investigation finds.

Anyone that has had a failure, particularly if you have had multiple failures, I strongly recommend you check your prop blade pitch to confirm they are within.1 degree (ideally exactly the same) and have a prop balance done to least .07 ips or better.

 

[Piper J3]

I wonder how coolant radiator and oil cooler are mounted on a AirCam? Engines are out in the breeze getting buffeted pretty good. AirCam originally had carbureted 912 and now iS engines. Maybe some research is in order.....

 

[mbell]

AirCam radiators are hard mounted on top of the center section. Never heard of one failing.

 

[mrpilotron]

Data.
There are lots of earlier build RV-12’s with lots of flight hrs, that are still flying with their original radiator. <snip>
I strongly recommend you check your prop blade pitch to confirm they are within.1 degree (ideally exactly the same) and have a prop balance done to least .07 ips or better.

I also love data and fully believe in the scientific method for analysis. The earlier RV-12s mount the radiator in a completely different location and don't hang the oil cooler off the bottom of it. The redesign for the iS model introduced a new dynamic that simply didn't exist on the ULS models so any comparison to them for longevity is invalid. I don't know how we might gather the data, but I would love to know the mean time to failure for 2-blade vs 3-blade prop aircraft. If my theory is valid at all, it should show a significantly different failure rate with 3-blade props.

Our 2-blade prop is very precisely set to equal pitch and dynamically balanced.

 

[rvbuilder2002]

I also love data and fully believe in the scientific method for analysis. The earlier RV-12s mount the radiator in a completely different location and don't hang the oil cooler off the bottom of it. The redesign for the iS model introduced a new dynamic that simply didn't exist on the ULS models so any comparison to them for longevity is invalid. I don't know how we might gather the data, but I would love to know the mean time to failure for 2-blade vs 3-blade prop aircraft. If my theory is valid at all, it should show a significantly different failure rate with 3-blade props.

Our 2-blade prop is very precisely set to equal pitch and dynamically balanced.

Typo….. early 12iS’s
The thread was about 12iS radiator so I didn’t think I needed to be that specific.

 

[mrpilotron]

Here's a quick pic of the #4 radiator showing the damaged fins between the lower cooling tube and the bottom mounting frame. This one was leaking less than #3, but it has about 2x more damaged fins. I assume this is due to fewer brazes pulling a hole in the tube when they got disconnected.
https://vansairforce.net/community/attachment.php?attachmentid=46635&stc=1&d=1692284292

 

[wsnodgrass]

Hi all,
I just wanted to add my name to this thread. I will be submitting an engineering report here shortly. We have a 2020 S-LSA RV-12iS and after 1300 hours, this will be our 4th radiator! We are a flight school, so I know that will always be a factor but a radiator should not leak on average every 450 hours. I suspect that this is a manufacturing issue. Not that it is a relevant comparison, but a Remos GX that I owned, has the same radiator after 4000 hours.
William F Snodgrass CFI-S, LSRM-A
Colorado Sport Pilot, LLC
The Flying School

 

[Amadeus]

After replacing the radiator with a new one from Van's ($800+) I took the defective one to a local radiator repair shop that specializes in aluminum radiators to see if they could fix it and have it on e the shelf for the next time. They just got back to me today with the news that the radiator cannot be repaired at an acceptable level of confidence that it will perform as required.

Until the "new & improved" method for installing the radiator Service Letter comes out then we are on the hook for buying and replacing a new radiator every year or two.

 

[bernsbm]

Help finding coolant leak

Looking for some advice on next steps to identify the site of a coolant leak in my RV12iS.

Problem: Over the past several flights I’ve found small amounts of coolant on the lower forward lip of the radiator during preflight inspection. Although the amount is small, I’m pretty sure its coolant (orange color, viscosity of coolant). Once I also found a few drops of coolant at the rear of the lower cowl (see pictures). Coolant level in the overflow bottle has fallen ~1/4 inch, the expansion tank is full. Coolant temps are stable and normal.

Investigation: Inspection of the cooling system found no obvious source of the fluid, other than the radiator (based on repeated findings of coolant on the lower forward lip of the radiator, always in the same general area, and nowhere else). I removed the radiator and inspected it with a magnifying glass, focusing on the area where coolant had pooled. I then pressurized the radiator to ~15-17 PSI and used a soapy solution to look for leaks. None were found. Lastly, I refilled the radiator with dex-cool 50/50, added UV dye and pressurized. No sign of leakage was identified with UV light.

Background: 2020 RV12iS with 320 hours total time. Dynamic balance since new 0.02-0.03 IPS checked annually. Blade pitch identical, tracking within 1/16 inch. Dex-cool 50/50 coolant used.

Repeated findings of small amounts of coolant on the lower lip of the radiator, in generally the same spot has me thinking there is a small crack/pinhole causing the leak. Not sure why I can’t find it. Maybe it only leaks when the engine’s running (vibration/hot coolant?).

Is my experience similar to what others have seen? Any more feedback from Van's?

Any suggestions on how to further investigate, and thoughts on likelihood of rapid progression? I have a new radiator on order, but they’re not expected before early next year (anyone with a spare radiator I could "borrow" until then, let me know).

Will be submitting a report to Van’s this week

Thanks, all suggestions welcome!

 

[DHeal]

There is a small weep hole for the water pump bearing located just below the water pump. It could be coolant weeping from this hole?

According to a ROTAX rep (Roger*), a small amount of leakage from this hole is not unusual.

See #75-00-00, Page 12, Figure 75-10 at : https://www.rotax-owner.com/manuals/MMH_912-914_Series_ED1_R6.pdf

------

* https://www.rotax-owner.com/en/rota...ons/7167-oil-leak-from-water-pump-912ul#21740

 

[Piper J3]

Use FJC 4926 Universal Radiator Coolant Dye and UV Flashlight Black Light (both from Amazon) to find source of leak. Works a charm....
-

 

[thiggins]

Use FJC 4926 Universal Radiator Coolant Dye and UV Flashlight Black Light (both from Amazon) to find source of leak. Works a charm....
-

There's a kit for oil leaks too, works. I thought I had a main seal oil leak, but the dye showed an oil pan gasket leak. Yay?

 

[Amadeus]

Is my experience similar to what others have seen? Any more feedback from Van's?

Any suggestions on how to further investigate, and thoughts on likelihood of rapid progression?

Exact same experience. It will continue to become more and more but only one (of the couple dozen reporting this issue) has been a rapid progression. Mine began at around 180 hours and I finally decided to replace at 230 hours when the puddle dripping from the back of the cowling overnight after flying over the nose gear wheel pant onto the floor got to be the 4 inches to 5 inches in diameter.

I'm not sure further investigation is necessary. It begins along the fins attached to the lower tank frame and slowly creeps across until the leak becomes more prevalent. I tried filling the bottom two rows with Marine-Tex but after doing so it hit me that Marine-Tex does not have any "give" or flexibility so perhaps you could try draining the radiator, cleaning the area then using the black, heat rated, RTV in the bottom two rows. However it doesn't seem any remedy has been successful.

Feedback from Van's is that they had come up with a Service Letter for a new mounting method/instruction. However this was just shortly before the cash flow issue and has likely become a lower priority task considering they are working hard to keep the lights on and doors open.

 

[Amadeus]

I tried filling the bottom two rows with Marine-Tex but after doing so it hit me that Marine-Tex does not have any "give" or flexibility so perhaps you could try draining the radiator, cleaning the area then using the black, heat rated, RTV in the bottom two rows.

I used a syringe like this:

https://www.neuromedicalsupplies.com/product/syringe-1-0ml-100-pack-small/

The tip fit nicely in the fin openings and pushed the Marine-Tex all the way through. If you have a nurse in the family you need just a few.

 

[docjjrmd]

Don't flame me but is this a reasonable alternative?

Alloyworks part number 536-51304D-BN

I don't think it could be worse than trying to glue up a repair.

 

[12vaitor]

You can also check ebay for this same aluminum radiator for $90. There appears to be several replacement 912 radiators you can select from. As low as $70 (poor looking welds), with most in the $90 range (decent looking welds).

John Salak
RV-12 N896HS

 

[Amadeus]

You can also check ebay for this same aluminum radiator for $90. There appears to be several replacement 912 radiators you can select from. As low as $70 (poor looking welds), with most in the $90 range (decent looking welds).

How would you mount these Model T and other various radiators in the small space within the cowling of an RV-12iS? Not to mention the routing of the coolant lines to reach the higher radiator connections rather than the bottom in and bottom out design of the iS radiator.

 

[docjjrmd]

The Alloyworks appears to be a specific drop in replacement for Rotax part number 997083.

see: https://www.rotax-owner.com/en/rotax-blog/item/25-newrad.

YMMV/FWIW

JJR