How do I install an oil cooler on my homebuilt?

I have an O-235 Lycoming engine. The assembly case has not been drilled to accept an oil cooler.

I called Lycoming Tech Service, but got no help. What needs to be done seems pretty clear, but I would like some technical advice. This engine is going on a homebuilt.


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I’ll apologize for my remaining colleagues at Lycoming for not being able to help you with your technical question regarding the installation of an oil cooler on your O-235 Lycoming engine. Your question is one that must be answered by someone who has been around for awhile. I guess that puts me in the “”old codger”” category — but at least I can answer your question.

In all fairness to the present Lycoming Tech Support staff, most of them may not even realize Lycoming produced accessory housings without machining, drilling and tapping the holes required for use with an oil cooler, so where does that leave us with solving your problem?

You need to locate an adapter that can be installed on your accessory housing and which allows you to install the oil cooler. The adapter is Lycoming part number 62418 and is available through any Lycoming distributor. A few words of advice: You might want to be sitting down when you check the price!

While doing my research, I was surprised that I could not locate this part in either the O-235 Parts Catalog or any reference to it in any Service Instruction. It is, however, shown and described in the Lycoming SSP-885-2, dated February 2003, on page eight of 12. You might check with your local maintenance facility to see if it has a copy of this publication. I also find it interesting that the only place the SSP-885-2 is mentioned is in the latest revision of Lycoming Service SL114, which lists all of the publications that are available from Lycoming. That being said, if you are unable to locate this information in your area, you can always order any Lycoming publication directly from the Lycoming factory by calling 570-327-7274, which is the direct line to the publications department.

After you review the information mentioned, I’m confident you’ll be able to proceed with installation of an oil cooler on your aircraft. Lycoming was involved with oil coolers on very few engine models, but allow me to offer a few suggestions that may be of some help to you.

First, since you failed to mention which homebuilt aircraft this was being installed on, check with others who have already built one and inquire as to where and how they mounted their oil coolers. This should save you some time and maybe some headaches. Second, I’d ask the size of the cooler used by others. If this information isn’t available, then I’d look at an installation on a certified aircraft with a similar engine and cowl and consider using that as a starting point. No sense reinventing the wheel, Grey.

Paul McBride, recognized worldwide as an expert on engines, retired after almost 40 years with Lycoming. Send your questions to:


  1. Tony Ilyes says

    The fix for the o-235 oil cooler adapter under the filter adapter is well known! My problem is the space between filter and mounting frame! No room to fit the adapter (cooler)!
    Can the acc. case be drilled and tapped to take the cooler hoses???


    • Al Kruckeberg says

      Just spoke with the fine folks at Casper Labs about this same issue. They advised that the accessory cases off of most Lycoming engines will fit the 0-235. The larger engines have the capability of adding oil coolers. If doing so you need to use the tach drive shaft out of the engine the case came off of. Do not know how this would impact the installation on a certified airplane, ie getting FAA approval.

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