The International Cessna^® 170 Association

Hi everyone—

I keep finding water in my 1956 170b's starboard fuel tank (not unusual for the wet coastal BC climate where I live).

HOWEVER, the water I'm sumping from the drain is rust coloured.

Does this mean my tanks are rusting, or there is some other part within the fuel tank which is rusting? I've heard the top fuel cap and mount assembly or can rust causing these issues, but I didn't see any.

It's worth noting the tank is not leaking at all. The port side tank has a new venting style fuel cap and there is no rust coloured water in that tank.

Thoughts?

I'm not sure how to upload photos, so check out the pics of the same forum post I made on Backcountry.com https://backcountrypilot.org/forum/rust ... 60#p346060

Well... the FIrst thing to note is that the vented cap is required by AD note to be installed on the RIGHT tank....and the pic shows what appears to be a non-vented cap.
As for the rusty water... I’m going to venture that your have rusted hardware at the fuel filler-neck and that old non-vented cap. You might also have a rusting steel fuel-drain or “curtis” valve. I’d suggest you replace the cap on that right tank with a serviceable vented cap and consider pulling the drain valve out for inspection. While it’s out...you might want to “flush” the tank to get all the water out.

Hope this helps.

GAHorn wrote:Well... the FIrst thing to note is that the vented cap is required by AD note to be installed on the RIGHT tank....and the pic shows what appears to be a non-vented cap.
As for the rusty water... I’m going to venture that your have rusted hardware at the fuel filler-neck and that old non-vented cap. You might also have a rusting steel fuel-drain or “curtis” valve. I’d suggest you replace the cap on that right tank with a serviceable vented cap and consider pulling the drain valve out for inspection. While it’s out...you might want to “flush” the tank to get all the water out.

Hope this helps.

Thanks for this. I'll replace the cap, drain, and filler-neck hardware.

Is the hardware for the filler neck part 41 or 30 here? ---> https://backcountrypilot.org/me/my-phot ... toid=57585

Also—I have the newer style fuel drain, not the Curtis valve, but it isn't listed in the parts catalog. Suggestions on a part #?



Sincerely,

Relatively new to aviation.

Do you mean a CAV-170?

DaveF wrote:Do you mean a CAV-170?

Yes, that's exactly what I mean. Is this the exact one I should order?

First off, join the association. Save yourself alot of grief and get all the good info you need. Is Mike doing your annuals? Good guy but the info here would be very helpful for him as well.
I know that plane somewhat, it was for sale in Vanderhoof a few years ago. Prior to that it might have been in Alberta and possibly sold out of Victoria probably 10-12 years ago I’m guessing but my date may be off there. I guess previously owned by someone who flew for Kiwi Air but that might have been somewhere else.
From your questions you could use some guidance and you won’t find a better place. As well, there’s a bunch of us in the lower mainland and most of us a members as well. Just across the border at S43 a bunch more plus instruction.
Not being critical here but your plane is interesting in that last time I saw it I guestimated I was looking at at least 4 planes. Doesn’t matter, just means its had a good life out there anfd should be good to you as well.
Rust issue as mentioned, likely your drain valve and filler neck and cap. Plane probably sat somewhere with minimal fuel, never a good idea. Be real careful removing it, use mouse milk or equivalent penetrating fluid to help removal. Filler neck that’s a bigger problem but likely the issue is the plane has sat for awhile with little fuel in the tank. Do you have a belly drain? Is the gascolator clean and has the fuel bowl drain been removed to clean out any debris? Should have been done on the annual but doesn’t mean it was and again you want to have that done to be on the safe side.
I’m in YPK PM if you need help anytime
Again godd luck and safe flying should the weather lift


PM me I’m in YPK if you need anything. Good luck and safe flying if the weather breaks

How much info is contained in this website ? ; if you do become a member, read everything here and understand everything, you’re probably ready to become an AME M1 (you also get an automatic Psy D degree if you comprehend all of George Horn’s posts)

George hit it on the head but I will emphasize it. If you haven't already found it I'm confident when you pull your sump drain you will see it is all rusted. Just replace it. This is the source of your rust. Actually water and this steel valve is the source.

GAHorn wrote:.... I’d suggest you replace the cap on that right tank with a serviceable vented cap and consider pulling the drain valve out for inspection. While it’s out...you might want to “flush” the tank to get all the water out.

Hope this helps.

Just to reiterate: I was suggesting only that you replace the cap, the drain valve, and flush out the tank. Although it’s certainly your choice, I would not be eager to change out the filler-neck or it’s assoc’d hardware if close inspection with a mirror doesn’t reveal something obviously unairworthy. (The filler-neck cavity is notorious for holding water after a rain or washing and it’s “threaded” into the tank and will need to be resealed (pro-seal) as it’s reassembled if you get into that. Also, the filler-neck is “clocked” during assembly to align the new fuel cap with the slipstream. Once aligned, it’s staked and sealed... why I’d not be eager to disrupt it.)

My tanks sat empty for almost 3 years during a rebuild, and had lots of rust on on the fuel gauge gears inside the tank, as well as the filler neck. You might be able check inside the tank with a mirror. I found it quite difficult to get all the rust particles out of my tanks. I flushed with water and Dawn dishwashing soap many times in an attempt to float out he rust but still got the occasional few particles on preflight for about a year afterward.

The drains need to be replaced every few years.

viewtopic.php?f=24&t=6106#p53000

Miles I thought that as well, the gauge mechanism. The aircraft has been sitting somewhere and having full tanks is a solution.

I agree George, best leave the filler neck alone. Checking the gascolator and keeping it clean, again will solve the issue.

Thanks all.

I will replace the drain valve with a stainless steel one to prevent the rust moving forward. I'll drain and clean out the tanks, but leave the hardware alone for now.

c170b53 wrote:First off, join the association. Save yourself alot of grief and get all the good info you need. Is Mike doing your annuals? Good guy but the info here would be very helpful for him as well.
I know that plane somewhat, it was for sale in Vanderhoof a few years ago. Prior to that it might have been in Alberta and possibly sold out of Victoria probably 10-12 years ago I’m guessing but my date may be off there. I guess previously owned by someone who flew for Kiwi Air but that might have been somewhere else.
From your questions you could use some guidance and you won’t find a better place. As well, there’s a bunch of us in the lower mainland and most of us a members as well. Just across the border at S43 a bunch more plus instruction.
Not being critical here but your plane is interesting in that last time I saw it I guestimated I was looking at at least 4 planes. Doesn’t matter, just means its had a good life out there anfd should be good to you as well.
Rust issue as mentioned, likely your drain valve and filler neck and cap. Plane probably sat somewhere with minimal fuel, never a good idea. Be real careful removing it, use mouse milk or equivalent penetrating fluid to help removal. Filler neck that’s a bigger problem but likely the issue is the plane has sat for awhile with little fuel in the tank. Do you have a belly drain? Is the gascolator clean and has the fuel bowl drain been removed to clean out any debris? Should have been done on the annual but doesn’t mean it was and again you want to have that done to be on the safe side.
I’m in YPK PM if you need help anytime
Again godd luck and safe flying should the weather lift

PM me I’m in YPK if you need anything. Good luck and safe flying if the weather breaks

Cheers! I joined the Association last night. Mike is not doing my annuals. Unfortunately, he told me he's too busy to work on my plane, so I'm still looking for a good 170 AME. I heard there's a guy in Qualicum Beach.

You're right—the plane has parts from all over. I've spoken with a few of the previous owners and learned some of its history.

I didn't see any rust on the chain, filler neck, or cap, so it must be from the drain valve. Could the fuel quantity gauge be causing it too?

I checked the lower drain below the engine and no water or rusty water is making its way through.