Radiator OK, plug not OK

[C10wip]

I recently installed a new Spectra radiator, the CU161 version which fits and is slightly larger and presumably better cooling than the CU162. Also, it's cheaper at AutoZone than RockAuto, which is a little unusual.
Anyway, it comes with a bypass plug/cap hose clamped on up by the filler neck. After only a month, I noticed that this plug was already cracking at the end. Not good! So, I am replacing it with a Dorman plug which appears to be a lot thicker but I am still a little concerned. The Dorman plug is part of a set, number 02253 so you end up with 7 other odd plugs. The plug ID is 11/16". Has anyone found a sturdier plug or better way to plug this off?
If you have installed one of these radiators and used the original plug, you might want to check it.

[gchemist]

Why don't you have a resevior installed? The neck connections goes to the resevior. It's Texas. When it gets hot, the plug is going blow right off when you turn off the engine.

[ElGracho]

He isn't plugging the neck. He's plugging the heater return hose connection. Some engines return to the water pump, some to the radiator.

[Katrina/10]

All those bypass caps are made out of junk rubber. Your'e better off with a piece of heater hose with a plug in it.

[C10wip]

Correct, the heater hoses return to the water pump and block so outlet this is "extra". I looked around some more and apparently this is a fairly common problem; supposedly the Dorman plug will last longer, a year or so but will give out. Kind of surprised there isn't anything decent ready made. So, I'll look for a small chunk of heater hose and something to plug it with. Thanks.

[Katrina/10]

The best plug is a copper water pipe cap.

[ElGracho]

It would also be easy to plug the hole in the water pump with a real threaded pipe plug and return the heater to the radiator...

[C10wip]

This water pump has a cast outlet rather than a nipple like I have seen on some.
So, I'll go with a plug - also from the plumbing section - a short 3/4" brass PEX test plug; this thing has ribs on it so it shouldn't slip out of the heater hose and shouldn't corrode. All for $1.53 at Lowe's!
The outlet is 11/16" and apparently it's better to squeeze the 3/4" hose down onto it than try to stretch the 5/8, if you even can.

[ElGracho]

Oh yeah, I didn't read the 250 L6 part. I have one of those also, I think all of the 250 water pumps have the cast heater hose return...

I'll shut up now.

[C10wip]

Not at all, thanks for the help. I see my truck is also "super duper plain" ...

[ElGracho]

I thought my 85 was plain. 4.3, SM465 4 speed, no cig lighter and no dome light. But at least it has power steering and brakes and gages. My 84 has a 250, 3 on the tree (now floor shifted) no dome light, no lighter, manual steering (I added power) and manual brakes. That's how I came up with super duper plain.

Both were cheap and straight. The 84 is even rust free and the dents are on parts that unbolt.

[C10wip]

Jschuder asked for pictures of the plug installed, and here they are. I used tensions clamps ( Corbin clamps ) because I had them from another vehicle, but I'm sure hose clamps would work just as well.

[y5mgisi]

Im having the same issue so i'll have to do the same thing.

[gchemist]

Nice plug!! I need bypass valve during the summer. Heat off the heater core is an A/C killer.

[motornut]

I'm using the doorman plug,thought they were for the carb,thats why they don't last very long.
(one a year,they only last that long on the carb anyway)
i like the brass plug idea better,didn't see those

[buddy_1]

--.

[jschuder]

Thanks for the pictures I got it all fixed up and no leaks I used hose clamps instead but like you said it worked just fine