O-235 Lycoming Blowing Prop Seal

[4930s]

Hi

[Cranium]

I don't know about the O-235, but the 540 can take two sizes - a standard size or an oversize seal (if the recess has been worn over many years and overhauls).

Other than that, check your oil pressure; make sure it's not too high. Make sure no one is starting the engine with the throttle forward more than a quarter inch or so - if a cold engine goes to 1500 rpm, oil pressure will spike severely.

[Strega]

Im no "engineer"

But I bet the breather is clogged up,,

[Hedley]

Looking for excessive crankcase pressure would be reasonable.

This can be caused by worn rings/cylinder walls resulting
in excessive blowby, or as Strega says, the breather plugging
up during the cold winter.

Make sure there is a hole drilled in the aluminum breather tube
inside the (warmer) cowling, so if the exposed outlet does
freeze over and plug up, it won't blow the front seal.

[Bulawrench]

check for cracked piston? The first time i saw this on a 985 i thought it was a varsol sprayer

[SeptRepair]

How many hours on the engine?

[cgzro]

Breather, make sure its not plugged up
Oil, make sure its warm before reving up
Oil pressure, too high (similar to second item)
Oil, what are you running?
Blow by rings, or worse , how is compression?

Is it being pre-heated? When is it blowing, at start up, or in flight?

[Strega]

forgive me If Im a little slow,

how does high oil pressure have anything to do with blowing the front main seal?

[Cranium]

forgot about the breather...

[niss]

forgive me If Im a little slow,

how does high oil pressure have anything to do with blowing the front main seal?

If your breather is clogged will it not show with excessive OP?

[SeptRepair]

Oil pressure is a function of the oil pump. I suspect through normal wear and tear the seal came loose.( they glue that holds the seal in place can break down over time) The seal spun and needed to be replaced. The new seal may not have been installed correctly or the AME used a split seal instead of a once piece( the tool to install a one piece costs about 100 bucks) The fact the seal failed again within 10 hours draws the attention automatically to something deeper than really may be happening. Human nature no one thinks they may have made a mistake on such an simple installation. They start thinking high crankcase pressures, blocked breather tubes maybe from ice formation, maybe from carbonized oil build up in the tube. The AME pulls the tube off and sees nothing whether be in the tube or the elbow coming out of the engine. Compressions are all fine. No oil on the belly and now he is scratching his head. Revisit the seal installation and this time throughly clean the surface the seal glues to, MAKE SURE YOU DO NOT GET GLUE ON THE CRANKSHAFT WHERE THE INNER SEAL RIDES!! There is a website called http://www.SacskyRanch.com and he has a good explanation on crankshaft seal problems.

[2R]

Nanook was on holiday in New Zealand ,when his rental car broke down .At the garage he was hot so he got himself a nice ice cream igloo sandwich.The cold white ice cream reminding him of his pleasant cold home on Baffin island.
In the heat it was a rush to eat the ice cream before it melted and he got some on his face.After he finished his ice cream he asked the mechanic what was wrong with the car .The mechanic said "It looks like you blown a seal"
To which nanook replied "get stuffed you sheep shagger"

[Strega]

Sept, ,

how do you install a one piece seal on the front of an O-235? never heard of that, ,
kinda like changing the alternator belt without taking the prop off...

[iflyforpie]

Sept, ,

how do you install a one piece seal on the front of an O-235? never heard of that, ,
kinda like changing the alternator belt without taking the prop off...

Kind of like childbirth, it is capable of large amounts of stretching and then returning to its (almost) original size.

[HS-748 2A]

(almost)

[fel]

Sept, ,

how do you install a one piece seal on the front of an O-235? never heard of that, ,
kinda like changing the alternator belt without taking the prop off...

I'm only an Aircraft Maintenance Engineer...and a Flight Engineer.....I used to be a Marine Engineer....and hope to be someday a Railroad Engineer, but how about using a.....
Seal installation tool! Go look at the Leavens Bros site.

Strega, say something nice about AMEs and I'll tell you how to change an alternator belt without removing the prop.

[SeptRepair]

Lycoming Service Instruction 1324C gives a detailed instruction about this topic. http://www.lycoming.textron.com/support ... I1324C.pdf The prop and starter ring gear must come off to do the one piece seal.

[iflyforpie]

Strega, say something nice about AMEs and I'll tell you how to change an alternator belt without removing the prop.

From the package to installed? Or by cheating?

[HS-748 2A]

Or by cheating?

Maybe he cheats like this guy? ...

http://www.youtube.com/watch?v=BQhfcdQf1QA

[Strega]

I know how to do it by cheating as well.. I think there is a sb somewhere that says youre not supposed to do it that way anymore...

[Strega]

Face the propeller end of the crankshaft and assemble the seal with the split at 1:00 o’clock on
standard rotation engines

I guess one piece really means split...

[fel]

Face the propeller end of the crankshaft and assemble the seal with the split at 1:00 o’clock on
standard rotation engines

I guess one piece really means split...

Nope, split means split and one piece means one piece.

The TWO crankcase front bearing oil seals used in Lycoming direct drive engines are the split seal AND the solid ring stretch seal. The split seal is open to permit assembly around the crankshaft. The solid seal is made from a highly elastic material that allows the seal to be stretched over the crankshaft propeller flange during assembly.

[fel]

Hi, I have an O-235 on a C-152 that has blown the prop seal twice in less than 10 hours, have done exhaustive troubleshooting but have not found a problem, the engineers are not comfortable signing it out without finding something they can attribute the problem too. Anyone got any suggestions?

4930's,
Is there just a leak at the seal or is the seal being forced out? What troubleshooting have the Engineers done? Have they tried a runout on the seal area with a DI to check for shaft true? Nicks, scratches etc on the seal area. Are they following the lycoming instructions to the tee, i.e. cleaning area with MEK, using 737, cure time, seal id? Heated hanger for the cure etc ? What is the oat where you are flying? Is the case vent line clear?

[SeptRepair]

Face the propeller end of the crankshaft and assemble the seal with the split at 1:00 o’clock on
standard rotation engines

I guess one piece really means split...

I take it you never read the Service Instruction.

[Heliian]

Is the oil actually coming out of the prop seal or has the crank plug become loose and is seeping oil? Don't forget to re-install the garter spring on the prop seal and glue it in there good.