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IO-360 through bolt leak fix

C

Cardinal767

I'm New Here
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
 
There are two case options that can apply. One is that there are dowels at the case mating surfaces that have orings there and that prevents the leak and supplies the rigidity necessary to support the main bearing journal. These don't normally leak and it doesn't sound like that is what you have as you had orings on the thru bolts. It sounds like you have the normal body fit setup and you may have some fairly serious fretting on the crankcase halves. Before doing anything else, I would retorque all through studs properly and make sure the engine doesn't get tight. If it does you are in for a complete disassembly and case overhaul/replacement. The fact that, the thru bolt wasn't torqued properly and it is leaking there, shows that the metal to metal fit of the crankcase halves has been weakened and maybe worn away and thus the main journal support that should be there, has been effected. If that is the case, on re-torque the missing crankcase material space is taken up and the main bearing gets tight on the shaft. If it passes the retorque test there is service Instruction 1290 on reaming the thru bolt passages and installing oversize thru bolts , as an in service repair. That will work if the fretting is minor and the thru bolt bores are not worn that bad.

Good Luck,
Mahlon
 
Thank you Mike for the welcome.

Thank you Mahlon for the advise, detailed advice was what I was hoping to get. Here?s more details on my end. I?ve been working the oil leak issue for several months since I bought the aircraft. It started with fixing the crankshaft seal which was actually free to move. Then I thought it was a cylinder base o-ring that was the next leak. After more cleaning of old stains, it pointed at the through bolts. I did a lot of homework and studied the IPC, SB?s, and overhaul manual. Finding o-rings on the through bolts THREADS told what I needed to know. Everything I?ve fixed was from someone else doing a poor job trying to fix the issues. After that, torquing everything was the next thing I did since an NTSB report pointed out what can happen if such things are done. Only the one bolt was what I considered under torqued. Like you said, turning the engine after torquing everything was when I held my breath. Everything turned freely with no difference in how it felt. Oil pressure and temperature was normal on all flights since after studying the Dynon recorded data. Oil sample I took 8 hours after doing this repair came back ?normal? this week. When I removed the one through bolt, there was resistance with a firm fit. I examined the bolt and saw no polishing from movement. The solution I tried was based on some of the repairs I?ve read using Loctite which basically holds the bolt firmly in place. I just tried to improve on it since I?ll probably overhaul the engine hopefully no sooner than 500 hours from now and I don?t want to hammer it apart. It has 1200 hours on it now and only 200 hours on the cylinders, but 15 years. I?m very happy to say that the inside of my cowling is still bone dry. But, I?m still getting something on my windshield and see streaks down my prop, I can?t tell if it?s grease or oil. Time to call the prop shop since it was just in there according to the previous owner.
So back to my question, does anyone see a possible harmful affect to the fix, and with the materials I used? I accept all judgements
To answer the question about my aircraft experience, I?m an A&P/IA with 35 years of experience. I fly fixed wings, sling wings, and no wings. I?ve overhauled several engines over the years, none have failed to my knowledge. This is my first experimental aircraft. In the past I usually steered away from working on them because owners tended to be automotive minded. Now that I own one, Ive brought this aircraft back to the aviation side, but I know that I can EXPERIMENT.

Thanks for any and all help

Bob
 
Yes sir, it’s a Hartzell CS, I was hoping it was grease since I couldn’t even find oil on the fly wheel or on the back of the spinner bulkhead. Thanks so much for the advice, I knew the four bolts you are talking about, but the picture confirmed it. I’ll try that tomorrow.
 
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