Cardinal767
Member
Afternoon everyone, first time poster. I bought an RV-8 with an IO-360 that had three through bolts leaking. I found O-rings on the treads of each through bolt that were obviously installed during the top overhaul years ago. Clearly they didn't work and I see why there is a SB on not doing such things. I emailed Lycoming about my possible solution two weeks ago, but absolutely no reply. After reading all the different fixes I decided to try something different. The bolts have smaller unthreaded areas and a larger center area that the original o-ring seals on. It's a firm fit but I was able to slide the lower forward bolt out to see what I could do since the bolt was not torqued properly anyway. I installed two O-rings just inboard of the larger threaded end of the bolt. Before sliding the bolt into position I applied Hylomar between the two O-rings because I was not sure the bore area in the case would be smooth enough for the O-rings to seal. I slid the bolt far enough to the opposite side to install two more O-rings on the other end, again just inboard of the threaded area. When properly positioned, every thing is inboard of the cylinder mating surface. I did all this without removing any cylinders and I always kept the remaining through bolts torqued properly per the Lycoming manual. The thought is, oil pressure will push the first O-ring into the Hylomar and the second o-ring against the chamfered area of the bolt and sealing it. The O-rings and the Hylomar are nonhardening and easily removeable, so when it time for an overhaul, I shouldn't need a big hammer and a heat gun to pull it apart.
10 hours after doing this repair, the engine is still bone dry. I'd like to hear any thoughts on possible harm this fix could have since Lycoming has never replied to me. Thanks
10 hours after doing this repair, the engine is still bone dry. I'd like to hear any thoughts on possible harm this fix could have since Lycoming has never replied to me. Thanks