[Buckeye]

I have an engine that has a through bolt that holds the two halves of an engine together. I think an O-ring on the through bolt has cracked/broken/destroyed and I am getting oil leaking thru the threads of the bolt. I didn't know if anyone knows of a good "putty/high temp tape to put on the threads to stop an oil leak?

Tired of putting in oil,
Greg

[johnsongrass1]

What engine?

[Buckeye]

It is an IO-360 Lycoming aircraft engine. It is a 200 hp fuel injection engine in a beechcraft sierra. I was just looking to see what everyone uses to stop oil leaks from an engine. I heard of some high temperature teflon tape and wanted to know if anyone has ever tried it or something like it? I really wasn't ready to do a major overhaul on the engine to replace worn O-rings.

Greg

[RGassman]

My o320 160 hp had the front o ring leaking out the bolt also, with a multigrade oil at 130 mph it would spread oil everywhere. When those cases are put together if they are not carefully that o ring gets damages or pushed out. Here's what my mechanic had me do. Pull the leaking bolt use a gun barrel cleaning rod and solvent and swab out that bolt hole, swab a bunch of red silicone in the hole focus on the O ring in the middle. Silicone the bolt and reinstall and torque correctly. I have a very very minor oil drop now and again. The alternative? tear her down and do it right just as well overhaul. I know a good mechanic for cheap in Oregon.
Most AP's will freak if they see silicon or teflon tape, not approved for inside that lyc, but they can complain all they want but they can't ground because of it.

Rgassman

[Buckeye]

Are you talking about taking the rod out? If that is the case, I am scared to damage the O-rings even more & also you need a brass punch & brass hammer to get that thing out! But we have tried to silicone the bolt twice with no luck. As you said, the oil just pours out. It is coming from the threads of the bolt. I didn't know about using some high temperature teflon tape? I don't know if anyone has used it before?
Greg

[Henry Highrise]

I ain't gonna go flying with you, Lmao.

[Buckeye]

I know this is a common problem with the lycoming engines. It is "legal" to slow down an oil leak from a through bolt. I am just looking to see what works best. Like I said, this is a common problem and I know people have dealt with it in the past. I just want to see what someone else did that had the best results.
Greg

[weirdbeard]

Originally Posted by Henry Highrise

I ain't gonna go flying with you, Lmao.

LOL! I was thinking the same thing. slathering tape and silicon on a car engine is one thing but when your life depends on that motor.... I would think twice about taking short cuts.

[RGassman]

My leak was the front case half bolt behind the prop flange. You could email Steve's aviation in Oregon Brian or Steve may have an idea for you. You could also with a warm engine remove the nut, put silicon on the bolt,put a piece of vinyl tubing over the bolt that has some slop, push the vinyl tubing tight against the block, take your air hose insert it into the vinyl tube and with air pressure try to force blow some silicon into the Small space where the bolt passes through the block, put your nut back on wait for it to cure then restart and check, maybe a copper washer under the nut? temp should not be much of an issue I would think, I barely hit 200 oil temp in the summer.

[RGassman]

Heres another thought from sacskyranch. This question came up with my 0320, if your breathers not breathing its gonna blow oil, front seal is typical but, It's worth a thought, for a sealer you might consider the plyable aviation gasket comes in a brush on can.
1. Crankcase pressurization. Normal Lycoming aircraft engine crankcase pressures range from 1-1.5 inches of water pressure in climb, zero inches in cruise, and 0.5 to 1.5 in descent. Lycoming specifications allow up to 5 inches of water maximum. However, no type certificated engine installations reach this level of pressurization.

An easy method of measuring crankcase pressures is to hook up an airspeed indicator to the crankcase, with the hose from the meter installed over the dipstick tube. The airspeed indicator would indicate 100 mph for a pressure of 5 inches of water or 50 mph for 2.5 inches of water.

High crankcase pressures can be caused by:

Blowby of combustion gas past the ring belt
Frozen or blocked breather vent

Ron

[RGassman]

For all you hot rodders out there, airplane engines may not interest you too much but heres some cool facts, we run 5" bores and long strokes with only 4 cylinders, making over 200 horses at only 2700 RPMS, Some are flat 8's with super chargers pullings some awesome horse power and we don't do it for just 11 seconds but from the time we mash the throttle wide open we may never back off more than 200 rpms for [U]hours. All this from an engine that only weighs a few hundred pounds. And no pullin to the side when it frags. My plane is totally old school, 1959, with a chromoly steel frame and fabric skin, 160 hp and it will run 142 mph all day long and "no speeding tickets" But you cant fly on the bad days so I mechanic on the 31 chevy. It is what it is.

You have time to spare go by air.

[johnsongrass1]

I wanna, but never known anybody to take me.

[Buckeye]

I called Lycoming and they are sending me an update to the engineering plan for the Lycoming engines (may 1997). They have made two ways of fixing the thru bolt. One is that you can now put in an "oversize" stud bolt or there is a way to replace to O-rings without tearing down the engine. I am not sure how that is done, but they are sending my mechanic the "bulletins" on how to do it. I think it will be another couple hundred dollars to fix it right, but it still beats a $31,000 overhaul. Thanks for everyone’s help and input. It was from the input that I finally figured out where the answer was.....thanks again.
Relieved,
Greg