37 Hours – Oil Cooler

Here’s an update from about 37 hours since the first flight. I found a few hours ago that I was getting high oil temperatures. This turned out to be an indication of several minor factors that were working together. First, the ambient temperatures started rising with the arriving spring season. Second, I didn’t really come up with an optimal mount for the oil cooler. I had it right next to the cylinder, but it’s really better for there to be some space between the cylinder and cooler. Also, I had the cooler mounted in such a way that it could trap air. A better arrangement would have been to have the inlet down low and the outlet at the highest point, which would naturally purge any air from the cooler. Another factor is that the 7-row cooler that I started with is probably a little bit too small. Bob seems to think that it should be adequate, but I read about many other installations where the 7-row proves to be too small for the angle-valve 360s.

To help resolve the problem, I’ve made several changes to the oil cooler arrangement. Note from the future- I’ve subsequently moved the oil cooler to the firewall. See this post. First, I found a 9-row unit. It is the same width as the 7-row, just a little bit taller. I removed the back left baffle and fabricated a new mounting system. The new mount scoots the oil cooler back about an inch, and also rotates it closer to horizontal. One thing that I haven’t yet done, but plan to do, is to flip the cooler over so that the outlets are on the top. A better arrangement would be to have the oil cooler sitting with the long dimension running vertically, but I’d have to make more extensive changes to mount it that way.

I have completed almost all of my data gathering. A few days ago, I flew down to Shelby to get some fuel. When I had topped off the left tank, I tried to install the fuel cap but found that the threads had seized. I had not lubricated the threads with anything, but Bob suggests a regular application of fuel lube to keep the threads from galling. I borrowed a vice from the friendly folks at the maintenance shop, and was able to use my onboard crescent wrench to apply enough force to snap the center male threaded part in half at the o-ring gap. This allowed me to separate the parts of the fuel cap. I borrowed the airport courtesy car and drove a few miles to the hardware store, where I picked up a 3″ long 6-32 screw and nuts. My plan was to drill the center vent hole and cut threads in the lower portion, allowing me to hold the cap together with the 6-32 bolt. The hardware store didn’t carry thread cutting taps, so instead, I drilled the vent hole up to the major diameter of the number 6 threads, and just used a nut on the bottom.

This arrangement worked to seal the tank, but not to allow for any venting. While flying on one tank is not an optimal arrangement (indeed, it is even advised against by Bob because of concerns about unporting the feeding tank during uncoordinated flight), it was sufficient to get me home for a 10-minute flight. The right tank was completely full, so unporting the inboard side was highly improbable.

Once I got back home, i was able to salvage the bottom piece of the cap, and of course all of the o-rings. I chucked the bottom piece of the cap into the drill press vice so that the vent hole was in line with the drill chuck, then I started increasing the size of the vent hole. I used about four sizes to get up to the minor diameter of the 1/2″ threads, which left just a few small pieces of the old male threads in place. I was able to pick out most of those pieces with a scribe, at least enough of them to allow me to get a thread cutting tap started. I worked it back and forth slowly and the threads cleaned up just fine. I used a steel bolt from the hardware store with coarse 1/2-13 threads to make a temporary center post. I drilled a 1/8″ hole through the middle of the bolt, which will allow the cap to vent. Since the bolt has a hex head instead of the airfoil-shaped vertical blade, cap removal requires a wrench. This gets me back to a flying condition while I wait for a replacement cap to arrive. You can be sure that I have since added some lube to the threads on the other cap too! I’ll use the repaired old cap as a spare, which I’ll carry in my onboard tool kit.

Posted on
Hours Logged This Session:
Total Hours: 1883.75