I went out to fly my Comanche 260 TC today and when I checked the oil level, the dipstick would not seat properly. This is a round dipstick, on top of the engine deck, inserts vertically, with markings every 3 qts. (12qt. sump, I keep at ~10 qts.) The top is a round cap, with a half-moon lift cam handle. There is a groove with an "O" ring below the cap that fits into the top of the filler tube. When I have inserted it, it 'pops' into the tube then 'locks' by pulling the lift cam handle from vertical to horizontal.
Now, the dipstick slides freely up and down the filler tube; no 'pop' and it will not lock in place. I am not sure what holds it secure (when it was working correctly); is it a vacuum when the handle is pulled down, or does the "O" ring expand, or ?
No mechanic on the field; does anyone know what I might check; where I might get an 'O' ring if that is thought to be the problem, is there a problem with the pins that secure the handle (it seems a little loose), etc. Any thoughts?

Sounds like the same style I have in the Twin - had this problem once and the mechanic fixed it - wish I knew how so I could pass it along.

Well 22G, good to know that it 'may' be fixable. Maybe an A & P will read this on his off day and send along a suggestion.

Hi Sam!

The tube that the dipstick goes into is plastic. Get up on a step ladder and check to make sure that the tube is not cracked. Check the o-ring to see if it is flattened. If so, then you may need a new o-ring. I am not sure whether it is a standard or special o-ring. I will look at mine next time I am out in my hangar.

The handle has nothing to due with holding the dipstick in the tube. The "O" ring does the job. bernie.

Alright...any married woman and female pilots can stop reading NOW.

Cleaned up dipstick and O ring area, out to hangar, wife on step stool inspecting filler tube which looks fine. I hand her the dipstick and she inserts it. I hear the audible pop as it seals itself in place. And again. And again.
Her: "Here, you try it, it seems to work fine".
I clamber up and try to mimic her success, without luck.
Her: " You are pushing down on the sides of the top, try pushing with your thumb in the middle of the top".
Me: to humor her, I use my thumb in the center, and POP, in it goes and seals.

In summary, the dipstick (which is also my new nickname, per my wife), needs center pressure as pushing with two fingers on the sides of the top seems to get it off center and it won't seal properly.

Instructional, but embarrassing. sb

Put a new O-rings on my IO320B1A dipsticks.... the same size as the old ones, but apparently a harder rubber, as I could not push it "home" with thumb and finger of one hand. After fighting it a few times, I found I could get two hands through the oil doors and get enough pressure to seat it. It's not going to leak any oil or fumes.

Al Powers

SB,

O my gosh - Thank you for sharing! Husband and I both fly so we have many many fun times between the two of us One good laugh deserves another.

We were having troubles with our Power Tow. We replaced several parts over several weeks and no improvement. Then we noticed the wear mark on the handle had changed. The set screw had loosened over time. We pulled the handle to the correct length and tightened the set screw Ta-da - perfectly operating tow again.