Hello Gang.

So....at our last 701 annual, we found that one of the radiator threaded mounts had come loose from the side of the radiator. From the looks of it, the mounts are a small tube that is flared in to the side of the radiator frame and then threaded with a 6mm tap. it is not a real mechanical connection other that the tube being pressed in to the frame and then flared slightly (like a riv-nut) to hold it in place.

The radiator is then mounted on 4 rubber isolation mounts that thread in to the side of the radiator and then on to the Zenair designed mounts which hold it in place at the right angle and location within the cowling.

Supposedly this is a rather common problem with these radiators. Enough so that when I asked what was the best way to fix it, our AME knew exactly what I was taking about.

He suggested some special epoxy that they use, but that this was just a bandaid fix.

We pressed the mounting stud back in to the hole, glued it, and then held it with lockwire until we could replace it.

We sourced a new OEM replacement radiator at a cost of almost $700!

Now I'm all for putting the best parts on an engine or airframe that are available, but $700 for a new radiator that is probable going to break in exactly the same way within a few hundred hours seems like a waste of money.

We went on a quest to see if there was something better.

Well surprise! there is.

We found an all aluminum (welded) radiator that is a direct replacement, right up to the threaded studs having the same 6mm thread. The size is identical. it is a direct bolt on replacement.

Notice that the mounting studs on the new aluminum radiator are welded right to the frame instead of pressed in.

The new radiator all bolted in, pressure tested, and filled with Dexcool.

The new style all aluminum radiator on the rubber isolation mounts and hung from the Zenair brackets under the Rotax 912 on a CH701

I would suggest that everyone check the 4 mounting studs if you are using this style of radiator set up. I don't think it would be issue if one were to fail in the short term, but 2 could be a disaster.

If anyone is interested in replacing their radiator, please feel free to contact me and I can let you know how to get one.


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Follow up.

After flying for more than 20 hours with the new radiator, everything is working great. The radiator is still solid. Cooling is excellent.

Thanks for the follow up Peter! So few do so. Can you provide a link to the source of the radiator? Or a part number and specs?


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