blue/fuel stain on carb - normal?

alpinelakespilot2000 · #1 10-24-2013, 04:04 PM

During my last oil change I noticed a bit of blue staining around the nut on the bottom of the carb (I'm not sure what it's called). I think it's probably been gradual enough that I just haven't noticed it before, and it doesn't seem to be much of a weep or leak, but what might cause it and what should I do, if anything, to address it?
Thanks.

crabandy · #2 10-24-2013, 06:44 PM

I'm not a carb expert, but on my Marvel Schebler MA4-5 I have a similar looking copper crush/lock washer that is probably seeping.

Vlad · #3 10-24-2013, 06:59 PM

Couple hundred hours ago I noticed this

Cleaned thoroughly and watched closely. Nothing since then.

alpinelakespilot2000 · #4 10-25-2013, 06:30 PM

Thanks guys. I'll keep my eye on it and keep looking for answers.

turbo · #5 10-26-2013, 02:52 AM

Clean it up, snug it down and keep an eye on it.

report back next month.

alpinelakespilot2000 · #6 10-26-2013, 02:14 PM

Quote:

Originally Posted by turbo

Clean it up, snug it down and keep an eye on it.

report back next month.

Thanks Ed. What do I snug down? The outer brass part or the inner silver hex-head screw? Do I need to keep one in the same position while tightening the other down?

turbo · #7 10-27-2013, 08:45 AM

clean it off first so you can keep track of the leak. put a wrench on the brass nut and see if it is a bit loose. check with your mechanic if this doent help.

az_gila · #8 10-27-2013, 10:57 AM

Quote:

Originally Posted by turbo

clean it off first so you can keep track of the leak. put a wrench on the brass nut and see if it is a bit loose. check with your mechanic if this doent help.

....

It is probably not a good idea to try and tighten any nuts that are safetied with a bent tab safety washer...

The correct fix would be to remove, replace the tabbed washer, retorque and rebend the tab.

goatflieg · #9 10-27-2013, 05:25 PM

This is just a guess... but could the blue stains be a side effect of combining dissimilar metals and aviation fuel?

aerhed · #10 10-27-2013, 05:55 PM

No, its just blue dye getting thicker as fuel vaps off leaving the dye. Common. Also common are small seeps like this with copper gaskets. Turbo hit it already. Crunch that brass into that copper a microturn and snug the tab flush again. Spritz it clean with a little electronic cleaner and check later. Done.