The International Cessna 170 Association

Hi all—

My gascolator is leaking from the fuel sump valve. When I sump the fuel by temporarily flipping the switch, the gascolator continues to drip after.

Here's my gascolator:

Can anyone help me with a part # for a replacement valve and gaskets? I couldn't find it in the 170 catalog.

- Reece
1956 170B

The picture you showed, not being that of the exact valve you have, we can not exactly help you.

What we can do is educate you a little so maybe you can help yourself. There are probably 3 or 4 valves that could be found in your gascolator. And there are several gascolators that could have been installed in your airplane over it's life. The quick drain valves available today are made by either Curtis or Saf-Air. See this page: https://www.aircraftspruce.com/categori ... alves.html.

The key to getting the correct valve or the valve that is currently installed, is to look at what is working for your situation. Look at and identify the size and type of thread it has. Identify if it is a momentary push style or a quarter turn locking style.

BTW there was a time when you could get a new seal for your old valve. They, with very few exceptions, are no longer sold. The reason is by the time a seal goes bad, it is likely time to replace the entire valve as depending on the design and manufacture, they can fail and fall apart.

According to the IPC fig 63, item 50, if you still have the original Kohler gascolator, a Curtis CCA-7450 is what the factory would have installed. https://www.aircraftspruce.com/catalog/ ... ickdv6.php

I have a paper envelope in which was shipped a bunch of the tip o-rings to which Bruce referred. Here’s the problem with them:

1-They are not really “O-rings”.
2-They are actually specially-shaped “seals”.
3-Using common O-rings can lead to loss-of-fuel (because being improperly-shaped they can fall off the tip and make an even larger leak.)
4-By the time the seals fail (dry and crack) the rest of the valve also likely suffers from water-damage and is rusted/corroded.
5-The entire Curtis or Saf-Air valve is cheap ... don’t screw this up by using the incorrect part (o-ring) or an old, shelf-life-limited tip-seal that’s been sitting in George’s hangar for 15 years.

Bruce Fenstermacher wrote:The picture you showed, not being that of the exact valve you have, we can not exactly help you.

What we can do is educate you a little so maybe you can help yourself. There are probably 3 or 4 valves that could be found in your gascolator. And there are several gascolators that could have been installed in your airplane over it's life. The quick drain valves available today are made by either Curtis or Saf-Air. See this page: https://www.aircraftspruce.com/categori ... alves.html.

The key to getting the correct valve or the valve that is currently installed, is to look at what is working for your situation. Look at and identify the size and type of thread it has. Identify if it is a momentary push style or a quarter turn locking style.

BTW there was a time when you could get a new seal for your old valve. They, with very few exceptions, are no longer sold. The reason is by the time a seal goes bad, it is likely time to replace the entire valve as depending on the design and manufacture, they can fail and fall apart.

According to the IPC fig 63, item 50, if you still have the original Kohler gascolator, a Curtis CCA-7450 is what the factory would have installed. https://www.aircraftspruce.com/catalog/ ... ickdv6.php

Thanks for all the info, Bruce.

My valve looks nothing like the ones pictured on Aircraft Spruce. As per the picture I uploaded, it's more of a quick flip drain valve which you simply 'tap' the lever to sump fuel.

Given none of the valves on Aircraft Spruce as the same as mine, does this mean I'd have to install an entirely new gascolator, or can I retrofit one of the new style valves to my existing unit once I know the thread spec?

GAHorn wrote:I have a paper envelope in which was shipped a bunch of the tip o-rings to which Bruce referred. Here’s the problem with them:

1-They are not really “O-rings”.
2-They are actually specially-shaped “seals”.
3-Using common O-rings can lead to loss-of-fuel (because being improperly-shaped they can fall off the tip and make an even larger leak.)
4-By the time the seals fail (dry and crack) the rest of the valve also likely suffers from water-damage and is rusted/corroded.
5-The entire Curtis or Saf-Air valve is cheap ... don’t screw this up by using the incorrect part (o-ring) or an old, shelf-life-limited tip-seal that’s been sitting in George’s hangar for 15 years.

Thanks for this.

As per my response to Bruce above, I'll plan to order an entirely new drain valve but mine looks nothing like the ones pictured of ACS. I'll go look at it closely today and take some photos.

Am I able to install the newer type ones pictured on ACS?

Ah, so though not a picture of your gascolator, the picture does show the type of valve you have. That type is found fairly commonly in aircraft. I don't know of the name of the manufacturer or current availability. Identify the type as size of thread yours has and replace it with an appropriate Curtis valve.

Bruce Fenstermacher wrote:Ah, so though not a picture of your gascolator, the picture does show the type of valve you have. That type is found fairly commonly in aircraft. I don't know of the name of the manufacturer or current availability. Identify the type as size of thread yours has and replace it with an appropriate Curtis valve.

Can I replace it with any Curtis style valve that's not the flip valve style I have?

reecewallace wrote:

Bruce Fenstermacher wrote:Ah, so though not a picture of your gascolator, the picture does show the type of valve you have. That type is found fairly commonly in aircraft. I don't know of the name of the manufacturer or current availability. Identify the type as size of thread yours has and replace it with an appropriate Curtis valve.

Can I replace it with any Curtis style valve that's not the flip valve style I have?

Yes. And I'd look closely at the Curtis CCA-7450 for it's suitability. After all it is the one called for in the IPC. Going on the assumption your gascolator is the original and has been unmodified, the factory felt it would work fine.

GAHorn wrote:I have a paper envelope in which was shipped a bunch of the tip o-rings to which Bruce referred. Here’s the problem with them:

1-They are not really “O-rings”.
2-They are actually specially-shaped “seals”.
3-Using common O-rings can lead to loss-of-fuel (because being improperly-shaped they can fall off the tip and make an even larger leak.)
4-By the time the seals fail (dry and crack) the rest of the valve also likely suffers from water-damage and is rusted/corroded.
5-The entire Curtis or Saf-Air valve is cheap ... don’t screw this up by using the incorrect part (o-ring) or an old, shelf-life-limited tip-seal that’s been sitting in George’s hangar for 15 years.

FYI, George is correct in that at least one manufacture, could be Curtis, could be Saf-Air, or maybe both by now, use a special flat washer style seal. However at one time and maybe still today, one of the manufactures did or does use a round cross section o-ring for a seal. It is very small and could be bought, at least at one time, if you know the correct number.

I have the same envelope as George of flat seals stored right next to an envelope of round cross section o-rings for these valves, you'd think I could put my hands on them easily. And I could if I remembered that special place I put them 20 years ago. You see I last used them to replace a seal on a leaking valve. Removed the valve, cleaned up the rust, replaced the seal, reinstalled and tested good. The next time out to fly a week or so later, the valve was frozen closed. You see, if the valve is placed correctly, it sits in any water accumulated in the tank. Once the cad plating on the valve is gone from rust, or removed to clean the rust, it takes little time for rust too reappear.

I've replaced bad valves with new ever since. It's a pain in the butt doing a job twice. Specially when it involves leaking gas running down your arm and burning your arm pit. We use to keep a new spare gascolator valve (probably a CAA-7450) and a Saf-Air CAV-170 for the wings.

Addendum: After writing this I was looking at the Curtis info as Spruce. Indeed it lists the seal as a MS29513-007 which can be bought. And Curtis still has a valve that might be suitable for an application, CCA-1150 TSO-C76 that they advertise as having replaceable seals.

More about Curtis valve that might be suitable for a 170 gascolator application. As I have reported the CAA-7450 is the Curtis valve called out in the B model IPC. I'm sure I've used other valves and now with a job that has a parts department in which I get to rummage for parts, I've notice that lots of these valves look the same though they have different part numbers. So what is the difference. Here is a part of a Curtis chart that shows most of their 1/8 NPT valves with an install height of .75". As you can see the differences in each might be the material the bodies are made of, aluminum, brass, cad plated brass and so on. The other differences are whether the valve can be locked open and whether the action spirals to lock or is pushed straight down then twisted to lock or maybe there is no lock at all. You will note the CAA-7450 is made of cad plated brass and is a push to open then turn to lock valve with only a lever on one side. I might prefer a CAA-1550 which is brass, has the same open and locking action, but has a lever out both sides which might make it easier and more positive to operate with a fuel sample tube as a tool. Of course both levers would have to clear the gascolator, but I'd think this probably wont be an issue.

Bruce Fenstermacher wrote:More about Curtis valve that might be suitable for a 170 gascolator application. As I have reported the CAA-7450 is the Curtis valve called out in the B model IPC. I'm sure I've used other valves and now with a job that has a parts department in which I get to rummage for parts, I've notice that lots of these valves look the same though they have different part numbers. So what is the difference. Here is a part of a Curtis chart that shows most of their 1/8 NPT valves with an install height of .75". As you can see the differences in each might be the material the bodies are made of, aluminum, brass, cad plated brass and so on. The other differences are whether the valve can be locked open and whether the action spirals to lock or is pushed straight down then twisted to lock or maybe there is no lock at all. You will note the CAA-7450 is made of cad plated brass and is a push to open then turn to lock valve with only a lever on one side. I might prefer a CAA-1550 which is brass, has the same open and locking action, but has a lever out both sides which might make it easier and more positive to operate with a fuel sample tube as a tool. Of course both levers would have to clear the gascolator, but I'd think this probably wont be an issue.

curtiswallchart-2013.jpg

Thanks for all of the info here. Some of the more technical aspects of material & locking mechanism are above my pay grade and aren't of a big concern to me.

It sounds like the CAA-7450 will be my best bet. However, how do I determine its thread pitch? I've measured mine, but there's no info on ACS about the CAA-7450. It only says 1/8" NPT and I'm not sure how that relates to my thread pitch number? From the looks of it, all the pipe fittings are 1/8" NPT so I should be okay to order anyone...?

From the Standard Aircraft Handbook ( Got my copy day one aircraft school 1978)
Had a British instructor Cy Tinley who tried to drive it into us concepts such as its called Pin cotter not cotter pin

c170b53 wrote:

104D6C32-A189-4B15-8A57-373042FAC542.jpeg

From the Standard Aircraft Handbook ( Got my copy day one aircraft school 1978)
Had a British instructor Cy Tinley who tried to drive it into us concepts such as its called Pin cotter not cotter pin

Well.... he was just tying to mislead you Canucks apparently...because when I worked at British Aerospace I was corrected smartly ...that its proper term is “split pin”. It would be inserted through the locking-holes of a castellated nut only AFTER the nut had been tightened with a “spanner”.

Yes, but did he use a “torch”or a flash light for illumination , Is a flash light a momentary bright light and then it’s darkness . The word “torch” speaks for itself.

And some of what we do with our aeroplanes is "fiddly".