IO360 - is a re-torque needed/recommended?

[Yourpilotincommand]

I have 350 hours SMOH, and wondering if there is a standard practice to recheck the case and cylinder torques? If so, how many hours would it take an avg A&P to do this?

[carusoam]

YPIC,

While we wait for an answer to that interesting question...

What makes you think this is a normal procedure?

Got something loose, falling off, or just leaking?

Best regards,

-a-

[Yourpilotincommand]

Nothing loose or falling off, but I do have an annoying oil leak somewhere around the back of the engine. I tried probing around with a borescope unsuccessfully. 

[A64Pilot]

I have never heard of a retorque based on hours. Actually if properly built and torqued I don’t believe one is required at all.

Back of the engine should be accessory case, and there are several places leaks can occur because of accessories driven off of the accessory case.

Best way to find them is to throughly degrease the engine and then run it up for a few minutes and look with a flashlight and mirror and use a paper towel to see if you can find any oil.

Especially if you fly it, the air can carry oil pretty far away from the actual leak

[ArtVandelay]

Good shops/mechanics use paint to mark a bolt that’s been properly torqued. You can visually check these.

[PT20J]

I don't believe there is any way to accurately check the torque by just applying a torque wrench to the previously torqued fastener. When you originally torque a fastener, the nut is moving until you reach the desired torque and stop. The friction of the nut is less when moving than the friction needed to get it moving again so the "breakaway" torque will be greater than the desired torque. When you attempt to recheck the torque with a torque wrench you are probably measuring the friction more than the bolt stretch.

In order to accurately retorque, you would need to loosen the fastener and retorque it. That's  likely to cause more problems than it solves. The official answer would come from Lycoming - I've found them pretty good at answering questions.

Skip

[carusoam]

Wait a second...

When you have an oil leak....

First step is to find out where it is coming from...

There are a few methods for that entailed around here...

Most methods start with a clean engine and work with a powder...

Next is the same thing but using a black light dye in the oil...

Once you identify where the leak is coming from...

There will be procedures for that too...

Your mechanic will know these steps too.

Often... leaks are caused by...

• a bad seal
• a cracked case
• aged plumbing
• I’m sure a loose bolt can cause a leak too... just not very probable...

Pics of what you know so far can be very helpful...  they tell a lot....   and they don’t misinterpret or add any extra meaning accidentally...

PP thoughts only, not a mechanic...

Best regards,

-a-

[A64Pilot]

I’ve seen case bolts be loose and cases leak from them, the real concern is that the case has “fretted” or worn when that bolt was loose. The few that I have seen stopped leaking when re-torqued, and yes you break torque on them one at a time and re-torque, so hopefully the cases weren’t worn beyond limits.

‘Many mechanics will use silk thread between the case halves, I use silk thread and Copper Coat, but I doubt Copper Coat is recommended by the engine manufacturers. I believe silk is preferred as I assume it will compress very thin and absorb a sealing compound and synthetic thread may not. Or maybe it’s just been used for 100 years 

The stuff used to mark bolts is called anti sabotage lacquer, a very popular brand name is torqueseal, so you will hear it called that, but I have used model airplane paint before, you want a thicker fast drying paint, the anti sabotage lacquer is more plastic like, it is the correct tool for the job. Place I worked at I had the inspection dept use yellow slippage marking, no one else in the plant was allowed to use yellow. so when you saw yellow, you knew it had been inspected.

‘Good mechanics will use it or a piece of chalk when they are final torquing whatever, it’s a way to make sure they don’t miss any fasteners 

Edited June 10, 2021 by A64Pilot

[RobertGary1]

Unless there is a problem I would just add torque paint. I did have a bolt on a piston end cap work loose 1050’hrs since factory new but you’d have to pull the cylinder to check that. That turned the engine case into corn flakes. 

[Yetti]

Mag seals, mech fuel pump seal, bad filter install, Start with the easy stuff

[Guest]

6 hours ago, RobertGary1 said:

Unless there is a problem I would just add torque paint. I did have a bolt on a piston end cap work loose 1050’hrs since factory new but you’d have to pull the cylinder to check that. That turned the engine case into corn flakes. 

A bolt on a piston end cap?  Do tell us more, I’ve never heard of such a thing.

Clarence

[PT20J]

Just now, M20Doc said:

A bolt on a piston end cap?  Do tell us more, I’ve never heard of such a thing.

Clarence

Connecting rod?

[RobertGary1]

20 hours ago, M20Doc said:

A bolt on a piston end cap?  Do tell us more, I’ve never heard of such a thing.

Clarence

It backed off so the piston rod only had 1/2 the end cap holding it on the crank. Mass destruction followed.