Going out for my second sortie and while in the climb with full power I got that hot oil smell and a bit of mist in the cabin.  Closed the heat control valve, reduced power and "bee-lined" to the airfield with good oil pressure while venting the cabin. Taxied in with good oil pressure to a shutdown in front of my hangar.

What a mess...I was down to just below the min line on the dipstick.  Luckily I have another oil cooler (AERO-Classics) on the shelf which I've been meaning to put on since this summer.  I've heard bits and pieces regarding the quality of the UL provided oil cooler and wanted to see if a different cooler might help out with cooling (and quality?)  Anyway, something to think about I guess...

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Ron -  is this your "go fast / hang around upside down plane?"  I was thinking of doing a Onex as my next project!!

Started to work on a top bracket to hold the oil cooler.  Will try going without rubber isolators on top, may go with them on the bottom/side brackets.  Bracket is 0.70" stainless steel, the bolts I just happen to find with a local aircraft parts guy AN3-40, and I used 5/16 steel brake line as spacers over the bolts.


Take a look see at ULP installation manual, ( up dated, page 38) oil cooler. It show it mount with 4 rubber absorbers. As for the OneX, build it for friend.


Ron Simonsen 

Thanks Ron...got it!  How long to do the Onex?


About one & a half years. Very hard plane for me build.

Hey Ron, thanks for the reply.  If it's not a personal issue, can you elaborate on what made it so hard to build?

For those planning on swapping out to the AERO-Classic cooler be prepared to do a significant amount of trimming to the lower cowl opening.  Best to fit your cowl with the AERO prior to paint and not basing the fitting on the ULP oil cooler form.  If you ever have to replace with the AERO-Classics later on you'll be glad you did all the cowl work prior. 

Got a chance to spend a couple days getting the new AERO-Classic oil cooler fitted.  Posted a few pics on my page. I'd like to say it was fun, but I cannot say it was my favorite thing to do.  Expect some cowl trimming, metal fabrication work, head scratching, etc.  I elected to go without rubber isolation mounts after exchanging email with the senior tech rep at Pacific Oil Cooler service (they make and service the AERO-Classic line).  He was uncertain if they would be helpful or not.  His best advice was to ensure to use long hardware with pinch tubes (I call them spacers or bushings) and pickup all 4 flanges for the mounting and securing of the cooler.  Based on that exchange and the fact that there are many GA aircraft installations with oil coolers bolted directly to the engine, and that this is not a ULP oil cooler install I opted for the "no rubber isolation mounts" option.  We'll see how that decision plays out over time I guess.  Anyway, did a ground run for leaks and to get the oil hot enough to open the vernatherm and circulate the oil thru the cooler.  Things appear good to go for a flight test tomorrow.   

Hi David, thanks for all of the info and pics. Your expertise, ingenuity and get 'er done ability is a great help to the rest of us. and your zenith is all nice and clean again.. Fly on.

Roger, Wilco!!


FWIW I have an AERO-Classic 10-row cooler on my Jab 3300.  The original Jab USA FWF installation instructions used rubber washers/bushings with the original 7-row cooler.  When I went to the 10-row, I deleted the rubber bushings because of clearance issues with the cowl.  Being a 6 cylinder, the Jab is an exceptionally smooth-running engine (my DynaVibe prop balance was below the limits of human perception!), but I have carefully watched the oil cooler mounting and have had no problems in 500+ hrs.



John, thanks for the cooler input!  I likely have the same model cooler - non PMA, and it is indeed a ten row vice a thirteen row I stated in my earlier post.  I feel fairly confident that the lack of isolation mounts will not be a problem in the long term - even with my four cylinder engine!  Compared to helicopters, these 750 airframes and components have a life of leisure regarding stress cracking, etc.  Having said that, I do plan on doing the DynaVibe balance on the prop later this Spring as soon as I fabricate a mount for the sensor pickup.  Just got to get over a couple of my own cracks...



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