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Andair Gascolator O-Ring

pa38112

Well Known Member
There is that old saying about "fool me once..." - I am really tired of the O-rings for my Andair gascolator. If you purchase the correct O-ring they do not fit tightly against the bowl grove, making it almost a sure thing that the O-ring will be damaged during assembly. I am tired of replacing it every year only to find that the new O-ring fits as poorly as the one I am replacing. From searching the forums I do not think I am alone with this problem. I use Fuel Lube on the O-ring, so that could be causing drag as I assemble it. Regardless, I have decided that I am going to replace it with a "proper" fitting O-ring. After {this part is re-edited after much o-ring sizing}. I have tried every conceivable size o-ring and found the a 2.5mm X 36mm is the perfect fit.
(Edit 6/25/2018 - After a year in service I had a VERY difficult time removing the glascolator bowl for my condition inspection. So hard that I was going to go back to the standard Andair o-ring, but when I installed one it was so loose that it reminded me why I started this investigation to begin with. I ended up re-installing a 2.5mm X 36mm o-ring and used fuel lube to lubricate it. I will report back next year. I would not recommend installing this o-ring without lubricant and I can't say for sure if lubricant will fix the removal issue.)

Below are photos of the Andair 2mm X 39mm and my replacement 2.5mm X 36mm. They can be purchased here: http://www.theoringstore.com/index.php?main_page=product_info&cPath=368_65_67&products_id=2776

Andair 0-ring:


2.5mm X 36mm Viton 75 O-ring:
 
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Grease

Just a thought.
I use the DOW silicone grease on my o rings.
Same stuff I put on the oil filter gasket.
DC-4 is what it is called, I just looked and it is recommended for oil filters but not fuel....but DOW has other silicones that are.

Fuel lube is very sticky....wonder if that just makes a not so tight fit worse?
 
Yes, I am sure the fuel lube is not helping with the install, other than it does help keep the O-ring in the grove.
I use Dow Molykote 55 on my other O-rings, but did not want to use it on the fuel system.
 
Does you follow the maintenance instriction?

Hello pa38112

Does you follow the maintenance instruction?

There it is mentioned, that you should use a NEW O-Ring, when you take the bowl of. This has a reason: The fuel will swell the o-ring over time. When you take the bowl of, the o-ring has now space to grow. After you cleaned the filter and bowl, your o-ring does not fit anymore, regardles which grease you are using. If you now force the bowl into position, you will damage your o-ring and generate a big risk, that the gascolator leak fuel and/or even greater risk, that your engine is sucking air ... and loose power soon.

I have found this situation by myself and two other buddy's ... I will do my two gascolators next weekend and will take a close look and make photos. I also have two o-rings from the last change, one year old on the shelf. I'm pretty sure they have again the original size ... they where swollen and dryed now. But I will not use them again.
 
Yes, I do replace them every time - that is my frustration. The new O-rings are not a good fit right out of the package.
 
O-rings

This is what I use.

2mm X 39mm V75 Viton O-ring Black

I order them through the o-ring store online. I tried 40mm, but they fit too loose.

-Andy
 
Let me check

Hello Keith

I understand that this is frustrating.

Let me check the situation next weekend, I have a few new o-rings from Andair here on my desk. Also the one that where in until next weekend and those that I took out last time.

I will report here.
 
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Thank you. I will be interested to hear how the different O-rings from Adnair compare. My son has my plane until next weekend. When I get it back I will try a few and see what fits best. I have the following to try:

- Stock O-ring from Andair
- AS568-029
- AS568-128
- 2mm X 39mm
- 2.5mm X 39mm

For full disclosure, the "Andair" O-rings I have are from ACS; however, I think it is a safe bet that they get them from the OEM.
 
No problem to change the bowl ...

Hello Keith

Today I opend one gascolator and cleaned the filter, put a new o-ring on and installed it again.

It was no problem at all! Also the old o-ring did not look'd bad/bigger!?

Old one:
gfLUsQYqM9skQwJB6

tw1L-efFD0MSEROurB_RtkYtt6LSyECpqcUvydqzTMzR-QGKn9bpK_IHOg0ebA9w026DAOdL6TXYfmL81-L-eNpFSChB7kSOnqBpagmaueQ5BDkBunLFATgH4F7PWEIiLyFZowUDrEMKYHBW0uLJSnzF_m0YSzWI8NbufB2Acs_X6DXiX9jtThC2zekM67JkB9uHs3Rnw7moJzfdaLtgwUXOY2nMgZjg9qb6kpg4n7SXHcsQeIqsMzg7vtyliAVZK3BZ-FLPwwGEogx-ofqNJ5y6Qs7lXXd_1e9CRl0V8w4tOX_Yw8T2d9gE9Fx9RCPCbfhLfpJ_zpijSlzesCBLDiJqw0maTfWzfWK8U9kdzGZTB4K5IkeSwnhY7DymxomdjXARxBAMtcPy6TvNg2jX70t54BXUo7TrmLw5mwRgxK1NODnSTeh2pydrOAaWUVqweAIOXFl9ZaJem-7xjsGcjfPeghPvNKbPyfml4wu4aHJXCtuqunFii46yeoZHXK7VRKwW_Tzy7luaveKzzkb_Rs9hY7_QfOPKB6o-Tu6lkvbXnaCLqkHy9bGewEwAMbn-35-hjK28JJ3L2ePCrm11PN96Ky-VUiy1tJPj_Q2rwHAIR7KGOVsHej_YIbexGmbjuVZe0jLMKpMcj-s-bv2HVxNWVnOqff5ATPNbX4wHkQ=w1252-h940-no


New one:
YZ7OojZepA5YEt3GzULjtIJzF4uO6ncrOz6Mfuhee_0vN38xhAQAeLvUUcXeadog1YzdvG_Z26QtGaD7thmoSieJhZ1jVsKYp-AuEKCNxYyFCPqNABFerMla5DNgLSbURUwXOB3LcuBuPMoIDxKwn8AplF9fvDiyygxrzAyHK8wurmuU9L5e02vYTUn3vlVVUXhUyjUb1mpPt49ZsUyTM7tbMsA0VOWkJpOeOHw-jm2KYuPIQ5qqO_mzeSQphGczUAfXv33YJW0RRMNndPabiyYNy9s8WCec4HrHT5F8GlK8aftoox2LaGKXWRk8SovkI88Rai5rrSexRCw2E-8as1VqJI3P1mgn7kfjQvqRMKB06mhqXDwx7H2AuagtQsQS4uY5LCbeF4VJAfTneWaNT0l_P5jKpY1aK1jgxsWmnAOzT2LYgr9wFUxZLzIdP-xZk5G8KiyFujMTUx_9RySw6S3tLwzfQ2CDh8gLLagzUEZZPRdkabQqwJlVKUhQfIMoBmErh6X_n8GMYzeiYM1yQSZlGo2HT8UvSRPWPZkP6ywgCFrGxpPwd9fuaXwdo7Jzu7v625_oZ49blMw6pUHwtQOcJ3EFnCurFczBorIpyuhkBwJE0c1M=w1348-h1011-no

Its difficult or nearly impossible to measure the o-ring size, because of the big diameter, you need a cylinder with the exact dimension to try and find out.

Toolshop is far away, so no quick trial.

I wonder if your o-ring that you purchased came like this or if your vendor buy them by himself someware else?
mi1LHE-nFfkfQeOGWQbmgOpfw-izP23yFv2nnGAuiA1v7ePNmLLPA6Mz3nNLot2JwimJp6OPA-jWXiUTlw006I7IexsqPy2mJ6cev9s97iT7YzF2OebD3WWuM3KCAQY2wH32Cf3DoyVkueXhmh6jcZyBIjB4hHtliYQofKfxWoJSo-pM4sfHL9p7qp7T5sxhnburNmklkRH1R9f8hXHFd_GHTgE7S2AcmpTnagqlKz4IAXIYNxY2ZBAdt2SyvgpRSDoxFIs6nbKqf4lBzi31-K-SNwlJTxXsMwRzC-1J2yH49ptNSbSwU7LYjbENzBlP39oL4-K3QTAonl7Srme-beQi9zJjrDDcyGk_gTDUAxUDltSWZ1ClT_Rl-s4tudx0E7MhtQqPVQG0XThFcHBDQjv6_rPFR0nPUJorg2VAO1VIKtg2uolebjq65RVEc9TbuwYNaoblz4ZJql-6AViZZ2U_Mzze4rEgdV8ahQWd4TV0N0c0M9whfAdj-10XVkXUVrY0aqBfJBoYEWa-MvkRYqpYcBEDa2C5DiB9u709u7WZbkm0vzz_xNZoG6Nb0cTfX7Ixxq4N7xl986C_HIM0xn1-vkdpYxb6AzXGa_VpboG3fnER=w758-h1011-no
fy4hQ5cmuQwAkOphITNiFv06REqCM7QxUcklVgxVVyiVJq4p-abyn74t86oLksfqPhn2tWsc5xCfrCEhOeCymfbChyM-2r1oDT53gbpVH7znaTg4l-bnTYZS5lE4zwPNiyF0ddApbrUNdKSSo0b8mVZvoQkSGWAJLfUFHCmZwScIAE5fmt5sh-sva4LOvpmZqbtIBmGBjJGKGvshXEAzXXskuigk9g8rxQQ6K31OPooNegSDZCu9OKLi6yYiVqfRBwPBUQfFL7EHXDe-MUMQEIKdyGSzTis301qS15YVQBszhzBeTHf1rbsE8G0sGGRgqHtV5Vymx-Y9X_t2BT1NyDQy6j3yPouKcd8MdqPPvjkQOGlBEmR2bRfDGq_dVi3Kmw0YaF7PXpLdRG213iOskGAkEPpLfY0HzxJYwuZ41T7QfNor1q-X2TK6zUDDlRAZr0_7SUmilwljFjLcAxGuGfy_XPnZwT92VkFHLw2MPvf7DivlKvAuT8qhUbhqG1R9Qzbxv8JGIhOO0KyaNt9m9hr4urMPZtshqgfWcLOluoSGunzbnA472J8zeouM_83Mg-ye1sOJAuxDcZJKal3qrFk7GKuWWBiLGgVwJMiCfrpQfurRcqn9=w758-h1011-no


I made a video where I install the bowl ... buy my iphone dont want to share it ... give me time to find out. https://goo.gl/photos/tV9XNosfGaXG5mJD7

I also was whiping around the seat of the o-ring on the cascolator-housing, with the finger that I was putting a small amount of fuel lube. Not a visible amount, just to not have it dry there.
 
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I would suggest replacing the filter at around 500 hours. On the threads there is a bit of a coating that, along with the pipe thread, seems to hold the filter in place. Mine got a bit worn and at the next annual I found the filter in the bottom of the bowl! There is no way of knowing how long it was like that during the year.
 
This weekend I tried several O-rings. Here is what I have found so far:

AS568-029 - Too small
AS568-129 - Too big
2.5mm X 39mm - Too big
2mm X 39mm - works, but seems a little too small

I will keep trying until I find the perfect fit !
 
Keith, how is your "original" O-Ring looking, when you purchased it from ACS? Like mine in the picture?

Check your PM!
 
I emailed Andair asking for size and material specs for the O-rings for the GAS375 Gascolator. Jenny at Andair replied: "The ORO375's are made from Viton 75, the dimensions are 39mm diameter x 2mm thick".
 
Thanks Kevin,
That is what I ended up with, but I don't like the fit. I think a 2.5mm X ? (36mm) may fit better. I just haven't gotten around to trying. The grove is 2.5mm X 39mm. I believe the ring needs to be smaller than 39mm to avoid my original complaint.
 
I have updated my original post so that those searching the forums will not have to read the entire post chain. I have found that a 2.5mm X 36mm is a perfect fit. It fills the grove, fits tight enough that it does not get caught when installing the bowl, and provides a firm seal - unlike the Andair o-ring, which slips in so easily that I wonder if it is even touching.
 
Excellent news. Be sure to keep us updated with long term performance issues if you see any.
Regards,
Tom.
 
I just took delivery of the O-ring linked to by the OP at theoringstore.com. It doesn?t quite fit - too tight (fat) for my Andair Gascolator purchased about 2001. My recommendation would be to stick with the original 2 x 39mm dimension, though I have also had two Andair O-rings shear upon reinstallation of the bowl and was hoping this thread would lead to a better fitting part. It hasn?t and I remain grounded until I get the right part.

Arlo Reeves
 
O-Ring swell in fuel ...

Hello Arlo

Stick with the original o-ring.

Your problem of shearing it upon re-installation is commen, the o-ring swell a bit in the fuel. So if you open it up to clean, the o-ring is a bit bigger and difficult to install without damaging it.

Try to lube it with a bit grase or fuel lube. I install ofthen a new on.

Hope it helps!

Dominik
 
I just took delivery of the O-ring linked to by the OP at theoringstore.com. It doesn?t quite fit - too tight (fat) for my Andair Gascolator purchased about 2001. My recommendation would be to stick with the original 2 x 39mm dimension, though I have also had two Andair O-rings shear upon reinstallation of the bowl and was hoping this thread would lead to a better fitting part. It hasn?t and I remain grounded until I get the right part.

Arlo Reeves
I m very sorry to read this - I would hate to think my recommendation has caused you problems and grounded your plane. I know that for my o-ring grove I used a caliper and made sure the 2.5 was the best fit. Did you use any lube when installing it?
Regardless of which size you choose to use, it is always a good idea to have 2 or 3 on hand. I started this whole search because of frustration with the stock Andair o-ring shearing on me repeatedly and being grounded like you.
-I hope you get your new one quickly and get back in the air.
 
No worries, I'm always game to try something different. It's quite possible that the Andair machining/anodization tolerances vary slightly or more likely that the O-ring durometer tolerances vary. Like you noticed, a 2.5mm thickness is a better fit for the O-ring groove, but the extra 1mm total thickness made the OD of bowl+o-ring 44mm or about 1.3mm larger than the ID of the gascolator. The 36mm ID also made the O-ring fit so tightly that it was hard to remove from the groove without damaging the O-ring.

With my 2001 vintage gascolator the OD of the groove in the gascolator bowl is 39.0 mm and the ID of the gascolator is about 42.7 mm. So a 2.0mm thick O-ring is compressed about 0.15mm whereas a 2.5mm thick O-ring is compressed about 0.65mm. I tried a couple lubricants but the extra thickness just required excessive force to get the bowl in. I finally did succeed, but not without chipping a couple small pieces off the O-ring, so I decided to wait for a better fitting part. Perhaps on newer units Andair has beveled the ID edge to allow easier insertion. My gascolator was the early style before they introduced the pleated filter element.

I did learn (re-learn?) a couple lessons from this.

First, if there's a part like this that can ground you, you should have a few spares on hand. I replaced my first Andair O-ring after 13 years in service with annual removal and replacement. I replaced it 2 years ago with a $15 part from Aircraft Spruce (I didn't order spare$).

Second, for all their beauty the Andair parts come with a price of not being easily serviced in the field because of their metric dimensions. I was unsuccessful in my attempts to locate metric o-rings of this size in stock in the greater SF Bay Area. I will be taking a spare O-ring or two along in the parts kit now.

And of course I should have hedged my bets on the first order by including a couple O-rings of the spec'd size. In the spirit of experimentation I did order a few different sizes this time 2 x 39mm as well as 38 and 38.5. One advantage the 2mm thickness has over the 2.5 is that they run cheaper - about $1 ea. vs. $3-4.

But I now have a few 2.5mm spares - PM me your address and I'll send them along.

Thanks,
Arlo Reeves
 
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I just re-edited my original post with the following addition:

Edit 6/25/2018 - After a year in service I had a VERY difficult time removing the glascolator bowl for my condition inspection. So hard that I was going to go back to the standard Andair o-ring, but when I installed one it was so loose that it reminded me why I started this investigation to begin with. I ended up re-installing a 2.5mm X 36mm o-ring and used fuel lube to lubricate it. I will report back next year. I would not recommend installing this o-ring without lubricant and I can't say for sure if lubricant will fix the removal issue.
 
Vacuum?

My fuel system is such that when the fuel selector is in the off position, the gascolator cover is basically locked on by vacuum. After finally figuring this out the gascolator cover is easy to remove. I use the original 2 by 39mm oring.

-Andy
 
Yesterday during anual inspection I broke my old original oring from Andair and I didn?t have a spare one on hand, so I starter to find one here in local market (Santiago, Chile), the only one that I found was Viton 2mm x 38mm, I installed with boelube and made a vacuum test with my mouth and tongue :D and felt like no leaking at all. I hope the new oring make a good job, I have to make a 2 hours flight with my wife today and some more to visit family next week

Cheers,
 
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