Boy is my face red

I installed my fuel gauge sending units with a stock rubber gasket coated with Fuel Lube because I thought I read that's a good way to do it. BIG MISTAKE. Both failed and started leaking 6 months later. The gaskets squeezed out just enough to leak. It may work if you don't tighten the screws too much or maybe skip the Fuel Lube. I pulled the tanks again and I'm prosealing them now. I also read that's a good way to install them but a bugger to remove later. Well, pulling the tanks again is a bummer too. Just an FYI.

Cadstat said:

I installed my fuel gauge sending units with a stock rubber gasket coated with Fuel Lube because I thought I read that's a good way to do it. BIG MISTAKE. Both failed and started leaking 6 months later. The gaskets squeezed out just enough to leak. It may work if you don't tighten the screws too much or maybe skip the Fuel Lube. I pulled the tanks again and I'm prosealing them now. I also read that's a good way to install them but a bugger to remove later. Well, pulling the tanks again is a bummer too. Just an FYI.

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The sending units can usually be serviced without pulling tanks. I resealed a sender (RV-6) by carefully working it out through the gap between tank and fuse.

Cadstat said:

...I also read that's a good way to install them but a bugger to remove later. Well, pulling the tanks again is a bummer too. Just an FYI.

Click to expand...

I agree that just proseal is the way to go. I have had to remove the prosealed plates and found that it wasn't difficult at all.

Flop tube option

You can service one sender from the outside but the other is on the back side of the tank if the tank was built with a flop tube.

The gooey brown Permatex "Aviation" Form-a-Gasket #3 sealant works perfectly well on cork fuel sender gaskets, no leaks after years and years (10 yrs on my old Cherokee, 7 yrs on a buddy's RV-4), and can still be disassembled much more easily than gluing everything together with proseal.

Heavy on the Proseal

I recommend if you are going to go with only the proseal, to put a nice thick layer, on the tank and the back of the sending unit. The proseal will seal up nicely and it will give you just enough clearance to get a box cutter blade behind the sender front plate and the tank wall to cut the proseal should you ever have to remove it agian.

I just had to cut out the access plate with a dremel, then use the box cutter from inside, the smaller hole, to remove the remaining portion of the access panel. There was no removing the sending unit though. The proseal was sealed good, but so little was used it was impossible to get a blade under it. For $27 I put in a new fuel sender with the new access panel and my fuel gauge works again. (So it is not all bad!)

IMHO,

Dan

Waitaminnit, guys, he didn't say the cork gasket failed. He said it was the rubber one. Now, I'm indifferent to which gasket you use on the big plate, though I have personally been happy with my cork gaskets, especially when I had to pull a tank open to install a fuel return for the AFP injection. I know another builder who had to do the same after using ProSeal and I can only say that I know a few words I didn't before... . But I'm having a hard time picturing how the smaller gaskets will be improved with ProSeal. To respond to the OP, I doubt the Fuel Lube was a factor; I'm betting you over-torqued the plate, crushing the gasket. And, yes, pulling the senders later, if you ever need to, will be a bugger.

Update

The fuel lube (E-Z- turn) is a synthetic grease. I essentially took a rubber gasket and greased it. I may have over torqued it but they were fine for 20 hours flight time and 6 months before the leak began but after removing them they look puffy like the grease degraded the rubber. The gaskets had migrated to one side on both tanks. The rubber gasket alone would probably be fine. I left out the gaskets this time and prosealed the senders to the tank.

425 hours on rubber gaskets with fuel lube. No leaks at all. I was cautioned about over-torquing the screws, so was very careful. I had to replace the RH sender about a year ago. Very easy job using this method.

Just another data point.