National Aeronca Association Bulletin Board

Anyone ever had a leak from the cylinder base, that seemed to be coming from the stud area? Lloyd is having problems with his C90-8 and has tried everything. He pulled the cylinder, and used sealant(the purple TCM stuff) on the studs and nuts. It seems to have stopped the leak. This one is new to me. Any ideas, advice? Thanks, David J.

It seems to me that some of those studs have an "O" ring around them. Its been a long time since I overhauled a small continental. I know some of the studs have "O" rings between the case halves.... If I had a leak around a stud, I would suspect that someone left the "O" ring out when they put the case halves back together. Might be worth trying a sealant, like you guys did, or perhaps a few turns of either a heavy silk thread, or dental floss.

Mike

David,
The earlier studded case uses sealant at the stud pad area. I use a thread there also. And now for the bad news, In two cases I had similar problems and found the case cracked at the center main into the stud boss. Both of the cracks were between the cylinders at the base stud. I pulled the nut off and sealed the suspect stud and it did work for a while. I found the cracking by removal of the cylinders.
If the leak stops great, mine had oil pressure decreasing as it heated. Down to about 10 PSI at 2300 hot, but normal on cold oil.
Paul

Guys, Thanks for the info. The leak was not between cylinders. It was at the lower front of the left front cylinder(sitting in the airplane). Real weird. Will keep you up to date as the hours go on. David J.

I have the same leak at the same stud. I contacted Triad In Greensboro NC and they said to remove the stud and put red lock tight on it before installing. I did so but still have the leak. I recently talked to Don Sword and he said the best fix is to drill the cylinder base with a counter sink bit just enough for an O-ring. Well I don't want to pull the cylinder for no more oil than I am loosing and certainly don't want to take the chance on improperly drilling the cylinder base. I'm only using a quart every 7 hours and have good oil pressure. For now I will just put up with the constant corrosion proofing the oil provides

If you are having trouble finding exactly where the oil is leaking then gunk the engine and when it is dry spray it with soft and dry deoderant (or any deoderant with baby powder in it). it will leave a layer of white talc and when you run the engine the exact location of the oil leak will appear. It will turn the powder dark very quickly. I have been doing this for years and deoderant is always in my tool box.
(it works good for the mechanic on a hot day too).......Jim

Guys, thanks for the help. It was coming from the front lower cylinder hold down stud on the left side(sitting in the plane). Lloyd pulled the cylinder and used the purple TCM sealant all over the treads and nut. 4-6 hours on it and so far no leaks. David J.

I wanted to check with you and find out if the oil leak is still stopped. Mine is leaking pretty bad now & and I really did not want to drill out the case and add an O-ring. Did Lloyd pull the stud completely out and put the sealant on the threads of the through stud that go into the center of the case or just put the sealant on the cylinder end and around the cylinder base?

He did not pull the stud out of the case. He used the purple Continental sealant that is $30.00 a tube. Coated the threads and whole area and put the cyl back on and so far it is dry. He also had a breather issue that was probably making the case pressure too high also. Hope this helps, David J.

You don't have to spend $30 for the Continental stuff. In their service bulletin that iists all lubricants and sealants, they cross a Loctite product (515?) that equals their product. A little cheaper. I found it through Graingers and Motion Industries (bearing company) also had it.

Brian Walker
'46 7 AC/DC

found it on Ebay for $9..thanks for the info