Manifold drain plug: seized

[Clucas]

The drain plug on my manifold is seized (corrosion) and won't budge. To date, I've tried multiple rounds of PB Blaster and tap-tap-tapping without success (not certain the PB is even getting into where it needs to go). I haven't tried heat yet but am admittedly skeptical that it will help.

Thoughts on how best to approach? I've thought about cutting it flush with the manifold, drilling it out and re-tapping, but have never done work of that type and certainly don't want to do any harm. The exhaust flange is in a similar state -- intuition says leave it alone since it ain't broke, but the practical side of me says this is the right time to do this.

Engine is fully winterized btw (by the book apart from draining the manifold via the forementioned drain plug). The plug has never come out in the 5 years I've owned her, but I'm looking to address some of these issues this winter.

Thanks in advance for your suggestions.

[hanleyclifford]

manifold water drain plug

If you are serious about cleaning out the manifold it is worth it to get that plug out any way you can. My experience with these manifolds is that to clean them properly you need to get every hole opened up and rodded out. In fact I have removed both expansion plugs and replaced them with 3/4" NPT plugs so that I could clean the chamber behind them. If you have not done this type of work before, best to let a machine shop do it. You'll be shocked at how much additional crud you get out.

[Clucas]

If you are serious about cleaning out the manifold it is worth it to get that plug out any way you can. My experience with these manifolds is that to clean them properly you need to get every hole opened up and rodded out. In fact I have removed both expansion plugs and replaced them with 3/4" NPT plugs so that I could clean the chamber behind them. If you have not done this type of work before, best to let a machine shop do it. You'll be shocked at how much additional crud you get out.

I'll be doing a pressure flush once we're in the 'safe' zone temp-wise to partially 'de-crud' the manifold -- probably won't go so far as opening up the freeze plugs. As far as the drain plug goes, part of me says to leave well-enough alone, but also feel it's putting off the inevitable.

Meanwhile... more snow tonight. (stupid groundhog...)

[hanleyclifford]

The cleaning value of that little plug is minimal compared to the other 4 holes. If you just back flush the manifold thru the two top (1/2" NPT) holes you will get almost the same result as if you had pulled the little plug. Take the nipples off and rod the chamber out with mechanics wire.