The Cessna 120-140 Association Forum

I recently purchased a 1946 C120. One thing I missed in the pre-buy was the wing fuel sumps. They are both rusted pretty good, one is completely clogged and the other dribbles fuel ever since I tried to use it. Are these replaceable without recovering the wings? Anyone have recommended part numbers for replacements?

This is my first airplane, so I apologize if this is a rookie question.

Thanks,

The valves are replaceable. Early tanks have a 1/4" pipe thread and later ones are straight thread with an o-ring, 7/16" IIRC. Curtis drain valves do not have replaceable seals (actually they do, but the life of the valve is sometimes not equal to the life of two seals,) so you have to replace the whole valve.

The straight thread valves have to be safetied to the sheet metal under the tank.

If your valve is crudded up to the point where it won't drain you have to wonder what the inside of the tank is like. I'd get to the bottom of it before you have problems in the air.

I agree!

When you go to replace the drains..........have buckets handy.

Several things can happen, only one of them good. (replacing the drain with a new part, as a simple off and then on) if you're quick, you can swap valves with minimal fuel loss. It helps to have a pal and a pail. You will get fuel running around a bit.

The bad things that can happen.

You could drop the drain and it gets away, now you decide. ..........do you remove your finger from the hole and let the fuel pour or stand around until someone fetches the drain for you.

The threads can get messed up removing the drain.

You have more fuel coming out than you have bucket.

Drain the tank through the gascolator before you try to remove the drain. That way you minimize the size of the potential leak.

Thanks for the responses. I agree, I want to take care of this ASAP. I hate the idea of going up without checking the fuel first.

I found this one that says it's made for early 120s (Mine is a 1946 SN 8574), however it says it's 1/4" NPT, not 1/8". If I grab a photo can you guys help me identify?

https://www.aircraftspruce.com/catalog/ ... cav160.php

Yeah, I think that's right. Look closely at the one that's in there now. If it's drilled for safety wire it is probably straight thread, even if it doesn't have the safety wire installed.

Why do I harp on this? Because I'm blessed with one of each...

(I did some checking, and I have corrected the original post, at least I think I have...)

John Cooper, I have straight thread valves with replaceable o-rings. The valves are drilled but but there is no tab to safety the valve to or other provision for safety wire. In the 12 years I have owned the airplane they have not been safetied and have not backed out. Are you telling me I need to find a way to safety these valves?

There is a piece of aluminum under that part of the tank. The drain protrudes through a hole in the plate. You can drill a hole near the edge of the (bigger) hole in the plate and safety it to that. I suspect you have later tanks in early wings, or someone just laid the fabric over the holes and didn't punch them through. (If so, you may be able to find them with some gentile probing.)

Early planes, hence early wings and tanks, had tapered threads and no safety wire was called for. The pipe threaded valves aren't drilled for safety wire, IIRC.

Here's a photo of mine. It does appear to match the one in the link I sent.