tight oil filler after mx

GeorgeC

GeorgeC

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GeorgeC
The oil filler cap on my O-200 is now really hard to remove initially, but subsequent removals feel normal. Is this something that will break in over time, or was the wrong gasket put on?
 
Right, but the next morning, it will be tight again. Maybe the gasket is deforming around the tabs on the cap?
 
Get a pipe wrench, or some large Channellocks.
 
It's not threaded, you turn it to the stop.
 
yes it could be the wrong gasket.
I did that with a fuel filler cap once, thought fuel lube would help til it got seated in; nuh-uh.
(so I doubt a little grease will help)
I'd double check the new gasket PN against the engine parts manual
 
GeorgeC said:
The oil filler cap on my O-200 is now really hard to remove initially, but subsequent removals feel normal. Is this something that will break in over time, or was the wrong gasket put on?
Click to expand...
Gaskets will compress over time - and become "loose". I suspect that you have the correct gasket - but it isn't broken in yet. Another factor is whether or not the engine is warm. Cold = a tight filler cap.
BTDT with the filler cap on my O-470. When the engine was fully warmed up it would leak a bit - some of which oil wound up on the windscreen (naturally the filler is directly in front of the pilot seat).
Unsettling - but the cure was as simple as installing a new gasket.

Dave
 
There are two types of springs used to retain those caps.

Each type requires either a thin or a thick neoprene gasket.

My airplane had the opposite problem. The thin gasket was installed in the flat leaf spring cap and was always loose.

With a new, thick gasket, the cap will be tight for a while, then loosen up over the years.
 
The oil filler cap on an O-200 is a turn-to-the-stop affair like a fuel cap. A new gasket will make it stiff. There is no torque setting. And yes, perhaps the wrong gasket was installed. Or the new gasket is of some sort of plastic instead of the old Buna. I've been seeing more of that sort of nonsense, and not just in aviation. Manufacturers use some substitutionary material that's cheaper or something, and performance suffers. Gascolator gaskets come to mind. In the household plumbing department, just try to find faucet washers that last even a quarter as long as the old ones did.
 
Mine does the same thing. I think it’s because after it sits a while the oil is squeezed out of the seal making it hard to turn where as repeated use keeps it better lubricated. You can try a little LPS on it to see if that helps.
 
Just evaluate it after you secure it. Just like that ‘free’ oil change at the dealership, the drain plug may be to tight. I guess to tight is better than quickie lube leaving it loose.

I just snug mine up, not to tight or loose, try it.
 
sourdough44 said:
Just evaluate it after you secure it. Just like that ‘free’ oil change at the dealership, the drain plug may be to tight. I guess to tight is better than quickie lube leaving it loose.

I just snug mine up, not to tight or loose, try it.
Click to expand...

On the O-200 (and A-65 thru O-300) that cap needs to be turned to the stop. There are little ramps in the filler neck that pull it down tight, and if you stop turning before the stop the cap might back off under vibration.

You might be thinking of a Lycoming or the odd larger Continental. They use an O-ring that gets compressed when the cap is tightened, and yes, they're often overtightened real badly. That O-ring compresses easily when hot and oily, and once it cools off and the oil has squeezed out you need a wrench to bust it loose. On the Lyc I was forever retightening and sometimes resealing the oil filler tube at the crankcase because it would get pulled loose against the lockwire by the force needed to break the cap loose. Had lots of fun trying to convince the other instructors and the students to just gently snug it. Gently. Never saw one of those caps come loose. I wish Lyc had a turn-to-stop cap instead. And a bigger filler tube.
 
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