Radiator Failure

As I posted several weeks ago, I had just taken off on my way to the Factory Fly-in when the lady yelled in my ears "engine temperature, engine temperature" and I looked down and CHT was rapidly climbing in the red. It was passing thru 360 F so I immediately throttled back to slow flying speed; it then settled in at 350 F and stayed there while I did a 180 back towards home. Keeping airfields under me at all times I limped for 15 minutes and landed back at the home field. A quick inspection with the cowl off showed coolant dripping from the bottom of the radiator and the belly of the plane and tailwheel wet with coolant. I opened the radiator drain plug and only got about a cup out, so it was nearly empty of coolant. A subsequent pressure test at a local radiator shop showed a split tube in the radiator core. Thru the whole incident the oil temp and pressure stayed in the normal green range. WARNING! FWIW the coolant overflow bottle was 3/4 full at the end of the flight when the rest of the system was empty! So be aware that a full overflow bottle does NOT mean your system is anywhere near full-you must check at the spider tank cap.

My failed radiator was the older brass/copper style. Today I just finished installing the new Kitfox aluminum radiator. It appears to be a much sturdier welded aluminum unit with stronger tanks and top and bottom supports, compared to the old soldered together unit. I understand all Kitfox Rotax FWF kits have come with this new upgraded radiator for the last several years. I wish I had known; my incident could have turned out far worse. The new aluminum radiator is a little thicker and taller and mounting holes are somewhat lower, so I had to make new mounting straps (3). Other than the new straps it fits in just fine and the existing hoses also fit. Installation is fairly straightforward as long as you take care to make the bottom and front face come out the same as the old radiator. I mounted the oil cooler on the front face using quick ties just like on my old radiator so that installation was quick and easy. If you are using the SS straps to mount the oil cooler they will need to be redone because of the taller radiator height.

Did a test flight today and everything seems good with temps all normal. By the way, I also went thru the Rotax Maintenance Manual procedure for exceeding engine coolant temperature. Since I was at 350 F for less than 30 minutes it required a thorough inspection and repair if needed of every coolant system component, and a torque check of all head bolts. Everything checked out good except of course the radiator.

I hope my experience may help encourage upgrading to the new radiator, as well as checking your coolant level often AT THE SPIDER TANK.

Appreciate the update and information Jim.
Very glad no damage to the Rotax.
Also sorry you missed the fly in. :(

Thank you for the update on your aborted trip. Great to hear that no other damage occurred. Wish I could have met you at the flyin, Jim, and your Kitfox.

Joe G.

I had a coolant hose burst three months ago.
The cht went skyhigh and the coolant came seeping through the firewall and over the floorboard.
Because the cht went off the scale (stops at 250) i went and put it in a field without further trouble, my overflow bottle was as empty as the rest of the coolant system.
Inspection of the engine showed no signs of overheating so I changed all the hoses and went flying again.

After about 30 hours of flying I decided to look under the airplane after a flight, and noticed the radiator blown up like a balloon.
Needless to say I changed it out immediately.

Seems to me that the old style radiators are starting to show their age,
and I would suggest keeping a sharp eye on them.
Luckily these 912's can handle coolant loss pretty well.


jan

Just an update on my radiator failure incident about two months ago. As I reported at that time that I flew home for about 15 minutes with CHTs at 350 degrees. I now have about 30 hours on the new radiator. I say this with tongue in cheek, but it seems to be true-the engine appears to be running better than ever (530 hours total). The oil level has not gone down even a little bit! Since brand new I have always had to add about 1/4-1/3 quart between 50 hour oil changes. Now after 30 hours there is no apparent drop in oil level. I am thinking the over-temp run for 15 minutes may have broken in the rings/cylinder bores much better than all the previous running. I'm still holding my breath and knocking on wood, but it seems reasonable that this is possibly true!

That’s fantastic Jim. When I heard of your radiator failure I was hoping there would be no damage. Perhaps a little Divine Intervention?

Yes, I was asking for Devine wisdom as I limped home.

Maybe Mr. Devine will chime in here :)