Tight oil dip stick

brien23

brien23

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Brien
Ongoing problem over tight oil dip stick on Lycoming O-320 and O-360 , people still snug it down and the next person has a real problem trying to get it loose. Telling people not to tighten it down after checking the oil does not seem to work.
 
Seems to happen quite regularly in our rental outfit. Usually take a pair of pliers and gently twist it loose.
 
2777-removal.jpg


https://www.sportys.com/pilotshop/dipstick-removal-tool.html
 
They have those dipsticks where u just flip a lever type thingy and it seals, not sure if U can convert to one of those.
 
brien23 said:
Ongoing problem over tight oil dip stick on Lycoming O-320 and O-360 , people still snug it down and the next person has a real problem trying to get it loose. Telling people not to tighten it down after checking the oil does not seem to work.
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Yeah, get the tool; ultimately, too tight is better than too loose when it comes to that oil filler.
 
Most pilots are afraid that the dipstick might come out in flight, so they overtighten it. It's silly. One way to reduce the problem is to install the red silicone O-ring instead of the black Buna-N O-ring; the silicone is much softer and doesn't offer the braking action of the Buna.

If you have to be using pliers or a wrench of some sort, you will eventually bust the tube loose in the crankcase. It's lockwired, but the lockwire stretches and will also break, and if that tube comes out you really do have a big problem in flight. Tell your renters and students that. You have to scare them into going easy on it. I wish Lycoming had a bayonet closure there instead of the thread.
 
Dan Thomas said:
Most pilots are afraid that the dipstick might come out in flight, so they overtighten it. It's silly. One way to reduce the problem is to install the red silicone O-ring instead of the black Buna-N O-ring; the silicone is much softer and doesn't offer the braking action of the Buna.

If you have to be using pliers or a wrench of some sort, you will eventually bust the tube loose in the crankcase. It's lockwired, but the lockwire stretches and will also break, and if that tube comes out you really do have a big problem in flight. Tell your renters and students that. You have to scare them into going easy on it. I wish Lycoming had a bayonet closure there instead of the thread.
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Do you have a part number for the silicone o-ring?
 
Normally I only use my thumb and forefinger and maybe middle finger to install the dipstick, never had a issue, I have seen people take a full grip as they install, not sure if they think it impresses other people or something, but yeah sucks when folks do that.
 
They always get tighter after a flight. I’m the sole operator of my Cub and don’t over tighten mine but it’s always pretty dang snug at the next preflight.
 
Stewartb said:
They always get tighter after a flight. I’m the sole operator of my Cub and don’t over tighten mine but it’s always pretty dang snug at the next preflight.
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The rubber expands when hot, so they'll be tighter immediately afterward. The oil you got on the tube's threads when you pulled the stick out is thick when cold and lubricates the O-ring when you screw the cap in. Then it thins when hot, runs off and down the tube, leaving the o-ring fairly dry and tight even after cooling off. Both factors prevent the dipstick's loosening in flight even if it isn't tightened much at all.

I've never seen one back out on its own.
 
It’s usually a dipstick that over tightens the dipstick!
 
I bet you could make a tool like that with a short piece of PVC and T connector.

0107_RodEndBearing_DriverWeb.jpg
 
Dan Thomas said:
One way to reduce the problem is to install the red silicone O-ring instead of the black Buna-N O-ring; the silicone is much softer and doesn't offer the braking action of the Buna.
Click to expand...

I’ve actually had better luck with the black o-rings than I have with the red ones. Not sure why but that has been the trend. Perhaps people are less aggressive when tightening them or something.

Regardless, I always carry a leatherman. It seems like at least 50% of the time I walk out to one of the rental airplanes with a student the dipstick is on so tight there is nobody with enough grip strength to get it off. I usually use that as a teaching lesson to hopefully get my students to just get it snug enough.

The push in dipsticks have their own problems. I’ve seen a lot of them that don’t get pushed back in like they need to be because people either can’t see them or understand what needs to be done.
 
Kenny Phillips said:
There was no "plastic tube" on my airplane.
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Some were aluminum, but the vast majority are plastic. Even if they're metal, an overtightened dipstick can cause the tube to back out of the crankcase.
 
My partners do that, tighten the damned thing gorilla tight.
 
Very common at our club too... you find yourself needing a Leatherman half the tight to loosen it

Kenny Phillips said:
Yeah, get the tool; ultimately, too tight is better than too loose when it comes to that oil filler.
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Should really just be finger tightening it. I've never heard of an issue with someone not tightening it enough, but have heard of plenty of stories of damage from over tightening.

Dan Thomas said:
an overtightened dipstick can cause the tube to back out of the crankcase
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Yup, had that happen once.. I went to go loosen the dipstick and the whole tube started spinning in my hand
 
^why I prefer what you find on the bigger Continental, just a big cap that does a quarter turn to lock or unlock
 
Bill Jennings said:
My partners do that, tighten the damned thing gorilla tight.
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have a little talk with Joey and ask him to "be the bad guy" and stress to everyone not to overtighten. you know, as part of things to look out for on the overhaul....
 
Tantalum said:
^why I prefer what you find on the bigger Continental, just a big cap that does a quarter turn to lock or unlock
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The small Continentals have a quarter-turn cap with the dipstick attached. The larger ones have an oil cap and separate push-in dipstick.
 
eman1200 said:
I think the point is that no one should need one of these things.
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Almost every FBO or flying club aircraft I've flown has this problem. I don't think a thread on POA is gonna change that. My suggestion was merely meant to offer an alternative to spending money on a tool, or to chewing up the dipstick cap with a pair of pliers.
 
Dan Thomas said:
The small Continentals have a quarter-turn cap with the dipstick attached. The larger ones have an oil cap and separate push-in dipstick.
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The one in the Cirrus (IO-550) has the quarter turn cap with the dipstick attached on a cable

Either way, appears to be a more elegant solution than the metal turn crank. Somehow that design just invites people to muscle into it with all their might
 
Tantalum said:
Somehow that design just invites people to muscle into it with all their might
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Many years ago I was a foreman in an air brake component remanufacturing plant. Air brake compressors, control valves and actuators all use tapered pipe threads of various sizes for the air fittings as well as for coolant fittings on the compressors. Cracked and broken pipe ports was a huge proble, caused by mechanics tightening them far beyond any reasonable torque. After all, it's the threads that take the pressure, and if sealant is used on them they don't need to be much more than finger-tight. I finally had cards printed up with torque specifications for all the various port sizes, and every product got a card. Even then there were a few that still busted stuff. The torques are surprisingly low.

The gas caps on cars are idiot-proof that way now. Instead of the old quarter-turn caps (which were vented) the manufacturers went to a threaded cap, probably to prevent people putting on old vented caps, and the cap has a ratchet-release mechanism to prevent overtightening. Maybe that's what someone needs to build for Lycoming engines. It wouldn't be difficult except that there are a lot of differing dipstick lengths.

Pilots don't seem to understand that there is no pressure being retained by that dipstick cap. All it has to keep in there is oil mist and some smoke. That's it. Gravity alone will prevent it's backing out.
 
Kenny Phillips said:
Yeah, get the tool; ultimately, too tight is better than too loose when it comes to that oil filler.
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I dunno, bout that. On mine, too tight squeezes the O ring out, and it will not only leak, but also be hard to remove. ;)
 
wilkersk said:
I bet you could make a tool like that with a short piece of PVC and T connector.

0107_RodEndBearing_DriverWeb.jpg
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I made one with two pieces of wooden dowel, the commercial one doesn't look it's enough for my plane.

The bottle opener on a Swiss Army knife works in a pinch, too.
 
Ran into something similar last week on a 172L. I'm not an engine guy, but I think that one has the O-320. There were two of us. He checked the oil while I preflighted. Engine was still warm from the previous renter that had just returned. We topped off the tanks first, then did the inspections. When I got around to the dipstick to do my own check, I couldn't get it loose. The other guy tried, since he had just checked it himself. He did not crank it down, but it wouldn't budge. I thought it might have been cross threaded, but I really doubt that was the case since it screwed in easily. I did have my Leatherman and we got it unstuck. This time I was the one that screwed it back in, and it still got stuck when I tried to immediately remove it. Don't know what the deal was, we let the line supervisor know about it and I haven't heard back.
 
Dan Thomas said:
The rubber expands when hot, so they'll be tighter immediately afterward. The oil you got on the tube's threads when you pulled the stick out is thick when cold and lubricates the O-ring when you screw the cap in. Then it thins when hot, runs off and down the tube, leaving the o-ring fairly dry and tight even after cooling off. Both factors prevent the dipstick's loosening in flight even if it isn't tightened much at all.

I've never seen one back out on its own.
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That’s what she said...
 
Matthew said:
Ran into something similar last week on a 172L. I'm not an engine guy, but I think that one has the O-320. There were two of us. He checked the oil while I preflighted. Engine was still warm from the previous renter that had just returned. We topped off the tanks first, then did the inspections. When I got around to the dipstick to do my own check, I couldn't get it loose. The other guy tried, since he had just checked it himself. He did not crank it down, but it wouldn't budge. I thought it might have been cross threaded, but I really doubt that was the case since it screwed in easily. I did have my Leatherman and we got it unstuck. This time I was the one that screwed it back in, and it still got stuck when I tried to immediately remove it. Don't know what the deal was, we let the line supervisor know about it and I haven't heard back.
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I ran into an engine like that. Either the cap thread was a bit too big, or the tube thread was too small, and it would bind.
 
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