Leaking Avionics Bay Access Doors

[jimmuse]

I have a normally aspirated '75 337G.

Does anyone else have a problem keeping the avionics access doors (between the engine and the windshield) from leaking? Know a trick to stop same?

My '67B never leaked, but the door arrangement was different.

Thanks,

Jim

[kevin]

Jim,

I *thought* I had this problem with my current plane, but it turned out to be a windshield leak, not the panels. Each screw in the panel has a little rubber seal on it, as well as the seal around the "gutter" for each panel. If these are kept in good shape, I have not had a problem with leaks.

Kevin

[Ernie Martin]

Peter's archives had a lot of info on fixing leaks into the electronics bay. Went to get it but the airframe archive won't come up (other archives do come up). Have messaged Peter to try to fix.

Ernie

[SkyKing]

Jim,

The avionics access door leaking problem has been the subject of prior threads, I believe on this website or Peters, where it was covered extensively. You might do a search first.

While you have the covers off, inspect the chain connecting your yokes for rust... which is a tell-tale sign of probs. You might want to shoot a little LPS on them as you get them rotated both directions.

Using a mirror look at the underneath side of the small cups that are attached and sealed with the greenish-gray putty stuff that Cessna used at the factory when they built the plane -- I forget the name of it. These are beneath the receptacles and we've seen them loose on several 337's, letting water in, or in the case of the P-models, a nice air leak. A quick fixit to seal out the water is to use a good grade of clear silicone, although the original stuff would be best. In either event, it's a messy and rather time consuming/tedious job to get each one of the cups sealed around its circumference. Perfect weekend project.

If the lip of the rubber seal isn't sticking up like it should so that it has some compressibility, that could lead to leaking water and air too, in which case you might consider replacing the seal... or perhaps laying down a bead of clear silicone on top of the rubber and let it set-up overnight without putting the panels on... this will give some additional height to make for a better seal. But DON'T lay a bead of silicone down and then attach the panels, or you'll play hell getting them off and may even damage the panel in trying to.

Hope this helps.

SkyKing

[EZCOPE]

I always worried about leaks - been in some hefty showers - zo I seal around the hatch with polyseam seal, pocket knife cleans out when access needed. I was never impressed with the factory drain system.
Good luck

[jimmuse]

Well, it's been a while, but here is the upshot.

One of the former owners had siliconed the access panels shut (ahem, Skyking, recognize this problem?)... and one of the former owners had opened them up... with a crowbar (seemingly).

Anyway, I pulled them off, took them to a really creative body man who couldn't do anything with them, as the two aluminum surfaces had separated, so they would no longer hold shape.

At my first annual since in my stable, when the a/c was returned to service, there was much blowing of fuses, etc. Seems that my FBO (not my mechanic) had done a wash, and the t&b and the d/g for the hsi both blew and shorted.

Nearly 3g's to r&r. The bottom of the d/g was totally rusted out. So much for silicone.

Anyway, I am looking for replacements from the junk fleet... I can only find the left one new at $800.

I appreciate all of the responses.

Jim

[SkyKing]

Jim,

Whoa... I don't envy your problem at all, Jim! This isn't the first time we've heard of this 'little' problem. Seems the shop that FORMERLY maintained our P337 did that little silicone trick on ours and actually glued them down.... they were a real bitch to get off. But we managed and without messing them up. A narrow and flexible stainless steel putty knife will ease the endeavor... and patience, LOTS of p-a-t-i-e-n-c-e! Probably best to clean all the old stuff out... 3M Scotchbright works really well to clean the alum after you get most of the nasty stuff off... then lay down the new seal, which is reasonably priced ... or at least it USE to be... from Cessna. Plio-Bond works best and let it set-up... and CAREFULLY lay the new seal down so that it's slightly elevated so you have good compressibility when you put the cover on it. It's also good to check the attachment hardware, as the ends can and do rust, and we've seen some rounded off... your wouldn't want to lose an avionics hatch cover... no telling where it would go (probably through the rear prop though!)... and talk about a sudden decompression if you're a "P"model! Oh, THAT could be fun... so check the hardware and REPLACE ANY that looks SUSPECT!

SkyKing

[Jack Moore]

the fix that i ran into twice is it isnt so much that the panel itself is leaking but there are two drain tubes running down from the tray under the fastners make sure they do not have dry rott or the clamp holding the hose to the nipple hasn't come loose....Jack