How to seal fuel sender

After a bit more than a year of flying, I'm getting some minor leakage (weeping) from the left fuel tank level sender. It seems to appear primarily when doing acro or steep turns. This is the standard Stewart Warner float type sender. I installed it without any pro-seal, but may have put perma-tex (non-hardening) on the rubber gasket. The weepage appears to be coming from one screw and maybe a bit around the gasket.

Does anyone have any best practice suggestions for this? I could always pro-seal it like everything else, but figured I'd pulse the group for any other good fixes. Just a nuisance leak where I occasionaly have to clean off a blue streak at the root fairing.

The new pushrod shroud springs seemed to have taken care of the oil drips I was getting

I would like to here from others as well, as I'm going to have to remove my left sinding unit as it quite for one reason or another.

I don't know why you couldn't just toss the thick rubber gasket and just pro seal it on?

It seems like that rubber gasket is so thick that it easily gets distorted.

Here is a link guiding you through replacement.

http://www.vansairforce.com/community/showthread.php?t=54790&highlight=replacing+fuel+sender

I would suggest leaving out the gasket and going with proseal only.

Yep - this got talked about a lot years back - haven't seen as much discussion in recent years, which leads me to believe that more have taken the option of pro-seal and no gasket. Mine seeped when I first fueled - the leak was from the screws, which the gasket doesn't really seal. When I took it all apart to proseal the screws, I was never satisfied that the gasket was going to seal at all, so i just left it out. No further leaks. It's how we'll assemble the tanks on the new -3...no use changing what has worked!

Paul

Head to the local hardware store and get a handful of #8 Allen head screws 3/4" long. Coat these screws with Permatex Aviation form-a-gasket and replace the phillips screws in the sender. You won't have to replace the gasket and the sender will come off when you have to replace it. If this doesn't work, then you can go the proseal route. BTW, it worked for me and hasn't leaked in 7 years. Don't crank down too hard on the Allen head screws, guten tight is enough! Also, wait several days before refilling your tanks. Good luck!

Jim

Another way is to use the screws with the viton O rings under the heads of them. McMaster Carr has them. Then you can go ahead and use the gasket. I've already had to replace a faulty fuel quantity sender in the 10, so I was real glad I had not prosealed it on.

Vic

Vans says toss rubber gasket.

Vans instructions on their drawing "Wing Float Wires" specifically says: "Discard rubber gaskets supplied with senders. Use tank sealant to seal sender to the access panel or rib."

How clear is that.

I have a friend who got his RV7 into the air for the first time recently. The following day he came back to the hangar and found avgas dripping onto the floor under the wing root. Yep, used the rubber gasket on the fuel sender.

He subsequently tossed the rubber gasket and used PPG Aerospace PR1428 B2 Access Port Sealant only. No subsequent problem.

Many builders use standard "Proseal" as used for tank construction (PPG Aerospace PR1440 B2 Tank Sealant or equivalent) for the sender but it is probably not the best product.

PPG Aerospace PR 1428 B2 Access Port Sealant (or equivalent) is resistant to fuel (same basic formulation as PR1440) but has lower adhesion specifically to allow easier removal of the access cover at a later date. Very commonly used in the certificated world for fuel tank access covers.

Yep, no gasket here and I just used a lot of proseal. I dipped each screw in proseal before tightening them up. So far so good.

Hey Steve, I wouldn't pull the plate to check the sender just yet...it may be a wire or connection under your panel. I'd go with the easiest fix first. Pull the wire on the tank first, then check to see if it has continuity to the back of your gauge (with an ohmeter).

thanks for all the help. I like the option of leaving the gasket and sealing the screws with form-a-gasket, but I'm also really tired of chasing that oil leak for 3 months and will most likely just go with the proseal on the gasket and screws. Fix it and forget it! I don't recall the van's instructions to throw away the gasket and seal the sender, but mine is a 6A, not a 7A. Probably a lesson learned incorporated into the newer model! Hopefully, since my sender has worked fine for over a year it will continue to do so .

lostpilot28 said:

Yep, no gasket here and I just used a lot of proseal. I dipped each screw in proseal before tightening them up. So far so good.

Hey Steve, I wouldn't pull the plate to check the sender just yet...it may be a wire or connection under your panel. I'd go with the easiest fix first. Pull the wire on the tank first, then check to see if it has continuity to the back of your gauge (with an ohmeter).

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Hey Sonny

I already checked the wiring and tested gauge it appears I have a problem with the sinding unit or my float came off. I will follow the advice of this thread and throw away the rubber gasket when I redo it.

vic syracuse said:

Another way is to use the screws with the viton O rings under the heads of them. McMaster Carr has them. Then you can go ahead and use the gasket. I've already had to replace a faulty fuel quantity sender in the 10, so I was real glad I had not prosealed it on.

Vic

Click to expand...

I have had to replace a sender on my -10 as well. I used the rubber gaskets with fuel lube originally, and on the replacement sender. No signs of any leakage in 2 1/2 years and 330+ hours. I was really glad they weren't prosealed in place when I replaced the sender. I think the secret is not putting much torque on those screws. The screws with the viton o rings sound like a good idea, Vic.

I prosealed the gasket in place. Four years and not a single leak.

Here's how I did it. Smeared proseal on the end rib, and pushed it into the platenuts. Put proseal on the cover and then lined up the cork gasket with the holes on the cover. Put the cover in place, dipped each 8-32 cap screw in proseal and put in place. Once all the cap screws were started by hand, I tightened them in a cross pattern, same as you would do to a five lug car wheel.

YMMV

My hope with using proseal and the gasket is that should I ever have to remove that cover, it will be easier to do.

Seal procedure for fuel tank plate (not sender)

What's the best way to seal the tank access plate? I followed the string on the sender and will ditch the rubber gasket on that. But on the access plate, cork gasket PLUS pro seal? just cork gasket with pro seal on screws? Washers or no washers? Ditch the cork gasket? Thanks for any responses.

Just from research on VAF, I concluded that tank sealant only with no gasket was the way to go to seal the cover plate to the rib. I also went with internal wrenching screws to facilitate easier removal should it become necessary. I don't recall reading of anyone having an issue getting the plates to pop loose if/when it became necessary. (The black goo is a much better sealant than it is an adhesive). My covers passed the 1 psi pressure test, but haven't yet seen fuel.

My research showed the cork gasket on the access plate to be a known problem, so I used proseal on the access plate and screws. However, I wanted to be able to easily get the sender out if it failed, so I used an automotive rubberized gasket material (cut and drilled to size) and used an anaerobic sealant on the gasket and on the screws. This material has held up well for me in auto applications.

I would avoid the rubber seal provided, as thick rubber is prone to cracking from age. The gasket material is a combination of rubber and paper and holds up for decades on auto engines. FYI, My wing was a quickbuild from 2000 and already had substantial cracking on the standard rubber seal.

Haven't fueled the tanks yet, but they held 1 PSI air for several days.