Radiator pipe plug, what the????? HELP!

[Cowboy_Customs]

The other day I was warming the truck before going out, (on my stupidity, ran it out of fuel due to the way it was sitting) While it was out ideling a plug came out of the raditor on the driverside, a 1/2" NPT does NOT fit! It wants to, but it doesnt! What size pipe plug do I need to get?? It looks like fine thread. It isnt a sperate oil cooler built into the rad either, its like for heater hoses as it drained the coolant out of the radiator. Fortunatly it is the top plug. Now I have no wheels so running back and forth to the parts store is NOT an option. I dont not want to gall the threads as I am thinking about using those ports now that I know what they do.

[VileZambonie]

Post pix 

[enaberif]

As far as I've ever seen there are no plugs at all on the radiator.

Some radiators may have hookups to put the transmission cooler lines in place.. is this perhaps what your talking about?

Sounds like a previous fix gone awry.

[zieg85]

Wonder if the radiator drain plug went out? 

[rockable]

"Wonder if the radiator drain plug went out?" 

Bingo!  Buy that man a beer!

[enaberif]

"Wonder if the radiator drain plug went out?" 

Bingo!  Buy that man a beer!

Radiator drain plug is usually a pet c0ck (sorry one of those words swear filters like) and usually on the bottom passenger side and he said this was on the top.

[Irish_Alley]

the only holes i can think of is oil cooler, tranny cooler and ac core but none of them link to the coolent idk I'm confused. doesn't take much but i am confused

[Cowboy_Customs]

Not a radiator drain. I did figure it out though. a 1/2 NPT is 18 threads per inch, but i needed a 1/2". So off to lowes last night, found that a 1/2" FLARE is 16 TPI. Screwwed right in no problem.
They are deffinatly 2 extra ports for something, I am going to have the radiator tested to see if my thery is correct or if they are for an oil cooler but the cooling tubes are cracked. I had that happen on a camaro that munched 3 trannys!!!

My buddy did suggest maybe they are for rear heating on Suburban?

[Captkaos]

If you are talking about holes on the tank on the radiator cap side, those are for the Trans cooler, it is an automatic radiator.

There was no rear "heat" on a Suburban, only rear AC.

[Cowboy_Customs]

Well the ports are on the driver side, as well has the tranny cooler ports on the passenger side which are used. I noticed last night the tranny cooler ports have reducers on them which the trans is threaded into.

Im just thinking now maybe they are for an engine oil cooler, but the cooler is cracked or flawed so the coolant is getting into it. Fortunatly for me it wasent being used. Im going to have it pressure checked when I do the Cummins swap.

[zieg85]

My 91 and 95 have oil cooler lines on the drivers side about that pipe size, but it shouldn't leak water out.

[rockable]

I stand corrected.  Glad you figured it out.