Weird Happening

That heater line is 20 feet long (or so it seems). You should at least replace the first 2 or 3 feet of the line at the connection to the head, this time.

 

I have success with Hylomar, Permatex Aviation seems common too. You could also use that on your old nipple if it is pitted/corroded, and that would help the hose seal as well.

 

If worse comes to worse, you can do what I did for this exact problem, but it will require removing the piece to work on it.
Buy a Fragola 484006-BL MPT Fitting (3/8 Hose Barb X 1/4 Black) from Amazon for $8.99 and a 1/4" NPT tap and drill set from amazon for $4.69 (https://www.amazon.com/gp/product/B01MDV3A30/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1) - Then just drill out the rotted fitting, tap the hole, coat the threads of the new Fragola fitting and you're done for less than $15.

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(before the hose clamp was installed)
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The right fitting is sold for $10.

 

of course the "right fitting" is the preferred solution -- however, the original fitting will most likely be destroyed upon attempting removal and the threads in the aluminum will also be un-usable because of the galvanic corrosion - this was what prompted the alternate fix with easy to acquire, low cost parts...

 

Hi Mr. Coppari,

A thought: continued corrosion/disintegration of that fitting is inevitable and at present yours appears sufficiently intact to probably remove without incident; if deferred until it breaks off you may find yourself having to remove in pieces (I think the crossover plenum#116968 is NLA).

Removal of the intake plenum and water crossover manifold is not extremely difficult, just a bit awkward. The fitting on my car - which was in a similar state - was held in place with a light grey sealant (the threads are not tapered), and with application of a propane torch I was able to unscrew the original without any damage whatsoever to the threads. Replacements are available in either aluminum (factory #106241) or stainless steel (Hill products), and I used the original version with Permatex water pump sealant, which was only a bit darker grey in color than what was removed. Gaskets are #132981 (x2) and O-rings #103039 (x2). Then not to worry about this for another several decades.

 

+1 on carlrose's advice - replace the fitting now if it can be unscrewed or you will end up with something like this and you will have to drill out and re-tap:
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My part 18 (Nipple in the rear (1-4) head) needs to be replaced.

I've been trying to break it loose for an Embarrassingly (VERY) LONG TIME.

ANY SUGGESTIONS on getting it OUT?

 

I was able to drill mine out. I first cut off the corroded stub near flush with the head, then used progressively larger bits until there was just a very thin bit of male thread left which I was able to remove with a mechanics pick. Did it with the motor out of the car btw, which certainly made it easier.

 

Maybe that's what I'll have to try.

Has anyone tried using IODINE?

Supposedly it "Eats" the Aliminum-Steel corrosion like a "Rust Remover."

 

Perhaps a dumb question but,

WHY put another STEEL Nipple back IN?

 

The Gavarino annodized Al one I linked to makes alot of sense. With some antiseize compound on it, it should last forever, and it has the socket aspect for future removal if required.