Fuel inlet strainer

[Scott Hersha]

Hopefully someone here has a solution for my issue. The fuel inlet strainer on my MA-4-5 carburetor is leaking. I removed the strainer for inspection last month during my C I. I used a new copper A16-A48 gasket when I reassembled it. It wasn’t leaking right after the condition inspection, but yesterday after a flight I removed the cowling for another reason and found blue stains around the strainer/gasket area. I removed the strainer and installed another new gasket. I tested it with the boost pump, and was still leaking. I thought maybe I had installed the gasket backward because it is similar to a spark plug gasket With a smooth side with slightly rounded edges. Installing it the other way around didn’t stop the leak. Next I looked for info in the Marvel-Schebler O/H manual. It says that the strainer should be torqued to between 35-40 inch pounds. I know had tightened to a much higher torque than that. Well it still leaks with the correct torque, no matter which way the gasket is installed. I’ve gone through 3 gaskets - only bent the tabs on the first one, but I’ll run out if I don’t figure it pretty soon.

What am I doing wrong??

Thanks

 

[Mel]

Have you inspected the surfaces that the gasket seals upon? If both surfaces are flat and smooth and the torque is correct, it should seal.

While you inspecting, look for cracks in the housing using a 10X jewelers loupe. If it was over-torqued, possibly the housing was cracked.

 

[WingsOnWheels]

Make sure the carb body and fitting didn't get cracked by the high torque as well. Make sure the strainer is seated properly and something isn't preventing the fitting from bottoming before full contact with the gasket.

 

[Scott Hersha]

Thanks for the suggestions. I did try/check those things. I finally got it to stop leaking. Here?s how....... I annealed the gaskets with a torch and quenched in water. I re-installed the strainer with newly annealed gasket, and torqued to spec, 40 in/lbs. it still leaked, so I tightened it a little more and it stopped leaking. I can only assume there are slight irregularities in the casting, and the softer copper gasket was squished to conform. I?ll be keeping my eye on it. I purchased 5 of these gaskets from Aircraft Spruce a couple months ago. I guess they were age hardened.

I asked my local mechanic about it. He said that when they have had this issue, he has put a thin layer of permatex #2 on each side of the gasket, and that has worked. If it starts leaking again maybe I?ll try that.