Oil Leak @ Thru Case Stud

[JMACFLY]

My oil leak got worse over the past 25 hours. I thought it came from the old seals in the push rod tubes so I bought 6 kits plus the spring compressor tool. Good tool, good kits. During the installation of the push rod kits, we found oil weeping around #4 cylinder (middle one on left side). Upon further inspection we found that the leak came from the Thru Crank Case Stud (@ the 10:00 position when looking at the crank case with the cylinder removed). A call to Continental felt like a call to the weather office. (How many of you have cancelled flights because some weather briefer in a windowless office tells you how bad it is outside). Well, the Continental guy tells us that they no longer support the C145 series engine. They still support the 0300 series but not the C145. He said that the leaky thru bolt was a precursor to dire things like crank case halves rubbing together and fretting, main bearings moving about in their race and creating a condition for crankshaft failure. The Continental guy said he would not run the engine again but would recommend overhaul.

Have any of you folks had this kind of leak? Did you goop sealant around the stud and put things back together or did you go the overhaul route. This is a 1500 hr.+/- engine, 2500 total time.

John

[FredM]

Luckily I have not had this problem yet. I have seen some posts on here before about the same problem. I think you were misled by continental. The only way you would have the problems they described is if the nuts
were loose on the thru studs. I would first check all the cylinder nuts for proper torque. According to my overhaul manual the thru bolts should be torqued to 490-510 in. lbs. The 7/16 cylinder studs also have the same torque 490-510 in. lbs. The 3/8 cylinder studs should be torqued to 410-430 in. lbs. If these all check good I am sure you won't have any of the problems described to you by continental. This Problem is most likely caused by the o-ring that is installed on the thru stud during engine case assembly, they are easily damaged during assembly. Unfortunately it can't be replaced without splitting the case. Your best bet would be to seal it the best you can. If you use RTV make sure it is oil resistant and you have to clean the stud repeatedly until no more oil is present, since nothing will ever seal oily parts. You might also try using an o-ring at the base of the nut. Personally I would do both at the same time. I would find the smallest o-ring that would fit and lubricate it with the RTV so it won't get torn while the nut is being torqued then I would fill the threads on the stud with RTV. Install the nut and clean off all the excess sealant.

Let us know how it works. I am sure someone else will have the same problem sooner or later.

[GAHorn]

Careful when playing with through-bolt torques on mid-life engines. If you change that torque, you can crush a main-bearing, or loosen it in it's race and cause it to spin. Remember that the case was supposedly torqued originally when the bearing was nice and new. Now that it's measurements have changed through operation, you can cause more grief if you upset the torque.
I agree with Fred that you probably got an inexperienced (possible new-hire) at TCM if he gave you that advice.
Try calling one of the older field reps who have experience with the C145/O-300 engines (and who know that TCM actually still does support the engine, they just don't offer factor remans/overhauls anymore) when you need good advice.
Use electrical contact cleaner to clean the stud area thoroughly, and use Permatex Aviation gasket sealant and a small O-ring to re-seal the stud at the exit point. Wait 24 hours before flying. I've used this technique on many leaking studs with no problems whatever.

[Kurt Aichele]

I know this post is old. It appears we are finding a few more oil leaks. It appears there is an oil leak at the base of #6 cylinder, between the bottom cylinder base stud and the thru bolt at the 4 o'clock position on the cylinder base. It looks like it is either the cylinder base "O" ring or the "O" ring that goes on the thru bolt stud. In order to replace the thru stud "O" ring, does the engine have to be disassembled, or can it just be pulled out and the "O" rings be replaced?

[Kurt Aichele]

Not sure on the "O" ring placement for the different thru bolts, but the "O" ring that we suspect is leaking is on the thru bolt that goes thru the case and secures the cylinder bases to the case. It's on an 0300D.

[johneeb]

Look at this picture and decide if you can remove a thru bolt with or without splitting the case halves.

[Kurt Aichele]

Thanks for the help. Will try it this weekend and update.

[edbooth]

I'm no expert, but after disassembling a C-145 to part out, I don't think you can replace the o-rings near the center of the through bolt without splitting the case.

I don't know if the C-145 and the 0-300-A are exactly the same, but the "O ringed " thru bolts on the 0-300 can be pulled without splitting the case. You do have to remove one of the cylinders that they go thru to get it out. Not a pleasent job since you have to disassemble a lot of the engine anyway.

[blueldr]

In my wildly misspent youth, I used to be acquainted with a very generous young lady that used some kind of "Cold Cream" that would really allow those O rings to slip in there.

[edbooth]

In my wildly misspent youth, I used to be acquainted with a very generous young lady that used some kind of "Cold Cream" that would really allow those O rings to slip in there.

Also it is a straight smooth bore and really nothing to tear up the "O" ring.

[blueldr]

If it was mine, I'd give it a try slipping new O rings in with plenty of lube on them.

[cessna170bdriver]

I'll have to check the photos from my 2006 overhaul when I get back to California, but I think the through-bolt holes in the case at the split are chamfered for o-rings. Also, I think the center shoulders of the through bolts are precision ground; that's what aligns the case halves. The rough part of the web castings don't necessarily line up exactly, but they don't have to.

[edbooth]

After disassembling two engines (one C-145 and one O-300) only half of the through bolts were able to come out without splitting the case. After lining them up without any bolts, you can see there isn't perfect alignment between the left/right case halves and the o-rings would catch on a small lip.

Like I said, I'm no expert and just interested to know if anyone has actually been able to successfully remove and replace the center o-rings without splitting the case and how they did it in a way that renders the engine airworthy.

Sounds like a defective case to me.

[edbooth]

I'll have to check the photos from my 2006 overhaul when I get back to California, but I think the through-bolt holes in the case at the split are chamfered for o-rings. Also, I think the center shoulders of the through bolts are precision ground; that's what aligns the case halves. The rough part of the web castings don't necessarily line up exactly, but they don't have to.

Your recollections are exactly right Miles. I have a dis-assembled case out in the hangar. The through bolts are chamfered for the "o" rings on a machined raised area that helps align the case halves. I can slide these through very easily. Of course as noted in this thread, is this the right way to assemble the engine ?...no. The question was can they be removed to replace the "O" rings without splitting the case ? Yes.

[GAHorn]

I had an oil leak at #6 cyl and the engine mount thrubolt which I stopped by removing the mount leg, cleaning the stud where it exited the case using aerosol electronics cleaner. After it dried, I packed Permatex #2 gasket sealant where the stud exits the case beneath the engine mount leg, slipped an O--ring onto the stud, then reassembled the mount leg and let it dry overnight. It worked like a charm at that location.