Mysterious water leak from speaker grille

[Bob E]

Here's one I can't figure out.  My '65 C is a ramp airplane and has never leaked water from the roof before.  But after a heavy rain a few days ago, I noticed water dripping from the speaker grille.  (See photo.) Not a lot, but enough to make a towel I draped over the pilot's seat back moist.  I thought it had to be a leak in the cabin air intake drain, but that's not possible:  The cabin air intake is a good inch or two lower than the speaker grille and water would have to run uphill, including over various indentations in the plastic, to reach it.  The only other place in the roof where there's an opening is the GPS antenna. It looks pretty solid, but just in case I smeared a very thin layer of clear silicone sealant around the base.  The next day the drip was back, or still there.  Any ideas?  (The top of the cabin door entry opening is solid metal and is also downhill from the leak.)

Edited November 27, 2020 by Bob E

[N201MKTurbo]

Maybe it is just condensation.

If the drain is clogged, the plenum could be filling with water and leaking from a higher point than the drain.

[0TreeLemur]

Your gps antenna is installed at a location directly above the overhead air plenum, which means that there is a cable penetration.  Most installers I've seen don't do that.  Rather they install it between the air plenum and the door someplace.   That plastic overhead panel is easy to remove.  I'd take it out and have a look.  Maybe experiment with one person outside with a hose, and another inside watching.   It could be that the plenum has a leak where the cable penetration is, and that is wicking water down onto the overhead panel near the speaker.

Good luck.

[carusoam]

My 65C liked to do that when the cover wasn’t on the plane....

You can test the drain for the air vent by putting some water in it... the water should drain down a tube to the outside...

If you can’t find the tube (near the wing) and water shows up... the tube may be ancient PVC from the days when your plane was built...

If replacing the tube is the solution... taking down the ceiling cover is the method....

How long ago was the antenna installed? That would have been a great time to see the the drain hose and cable that operates the vent... two things that don’t age very well after 50years... 

PP thoughts only, not a mechanic...

Best regards,

-a-

[Bob E]

Thanks for all these suggestions N201MKTurob, OTreeLemur, and carusoam.  I agree that I'll probably have to remove the ovehead panels and test for leaks by pouring water around.  If I don't remove the panels I'll only be able to confirm where the leak is but not what's going on.  The GPS antenna was installed four years ago.  The air vent drain pipe has never been replaced, and the last time I looked at it was 10 years ago when I replaced the open/shut cable mechanism. 

 

[carusoam]

Bob,

Expect that it takes a lot of water to make drips show up there...

So... it is probably less likely that a properly installed antenna would behave that way...

Best regards,

-a-

[mike20papa]

My A model has the speaker mounted thru the cabin roof with 2 - #10 screws.  I see one #10 (?) screw about 6" forward of the GPS antenna.  You might check it.