3.0L Exhaust Manifold Drain Plug

[TyeeMan]

Happy Friday!

1989 Merc 3.0L, the 1/8 NPT threads in the water drain on my exhaust manifold are getting a bit beat up. I cleaned up the threads with a pipe tap last year but after that now the brass plug is barely long enough to engage the threads as much as I would like.
My question is, is there enough metal in that area of the manifold to enlarge the existing drain hole to a 1/4 NPT thread? Or can I get a longer brass plug from a Merc dealer? I've looked various places and am having no luck finding anything like that.

Thanks

 

[Don S]

Re: 3.0L Exhaust Manifold Drain Plug

It's a tapered pipe thread, when you use the tap to clean the threads, you should only be cleaning the threads not tapping the threads deeper. To prevent needing to clean the threads, just put the plug back in after draining, a little grease, or gasket sealer keeps them from rusting.
To fix your's, get a short brass pipe nipple and install it. Since it doesn't have a head on it, it can go deeper. IF it hits the inside of the manifold, just grind of some of the threads. Then, get a cap for the other end of the pipe.

 

[Bondo]

Re: 3.0L Exhaust Manifold Drain Plug

I cleaned up the threads with a pipe tap last year but after that now the brass plug is barely long enough to engage the threads as much as I would like.

Ayuh,... Does it Leak,..?? If Not,.. Don't worry about it...

 

[TyeeMan]

Re: 3.0L Exhaust Manifold Drain Plug

Thanks guys! I'm just trying to clean up what the PO did. By the time the tap engaged any threads it was already up to the bigger part of the taper.
I'll go get a nipple and cap. Gotta like those easier fixes.

Thanks again!