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#1 Old 03-16-2010, 06:12 AM
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radiator drain petcock

I finally installed a new radiator (Proliance).

When I went to install the drain petcock, much to my surprise the hole in the bottom of the radiator was too small for the 1/4" NPT fitting. So I went and got the next smallest size petcock, 1/8" NPT, and the hole is too big.

Is there a 3/16" NPT size petcock? Guy at the parts store said no.

Why in the world would this radiator have an oddball-size hole?

___________

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#2 Old 03-16-2010, 06:58 AM
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Metric???
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#3 Old 03-16-2010, 10:09 AM
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I'm guessing that 383 is guessing right..
Doncha' love finding this stuff out after you have something installed and all the bolts tight?

Yeah, there is no such thing as 3/16" pipe thread and there is also no such thing as 'metric' pipe thread...

It's probably some metric size thread where the drain plug uses an o-ring to seal. If you have a set of metric taps, you might want to run a tap in the hole to figure out what size it is. But be careful as metric stuff has different thread pitches also.. Don't want to bugger up your threads.

Jeeeeez. You'd think if they were gonna go 'different' on a new rad, they'd at least of supplied you with the right draincock...

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#4 Old 03-16-2010, 11:12 AM
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I had the same problem with my rad so I ran a 1/4 NPT tap into the hole.
Works now.

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#5 Old 03-17-2010, 05:37 AM
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Originally Posted by 3834B View Post
Metric???
Could be...why the @##$!& would a big old radiator for an old American vehicle have a metric thread, though? Seems odd.

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#6 Old 03-17-2010, 05:44 AM
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Originally Posted by bherder View Post
Doncha' love finding this stuff out after you have something installed and all the bolts tight?
I'm kicking myself for that, as the thing was sitting in my workshop for 2 months and I could've easily checked it. Never even occurred to me that it might not be 1/4" NPT.

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Originally Posted by bherder View Post
It's probably some metric size thread where the drain plug uses an o-ring to seal. If you have a set of metric taps, you might want to run a tap in the hole to figure out what size it is.
I'll pull out my metric thread chasers and see. I'm guessing I won't be able to get a petcock for it, though.

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Originally Posted by bherder View Post
Jeeeeez. You'd think if they were gonna go 'different' on a new rad, they'd at least of supplied you with the right draincock...
It had a flimsy-looking plastic "plug" in it that I assumed was just to keep dirt, etc. out during shipment. It was not threaded, just pulled right out. I chucked it during the installation.

Is it possible there is a bushing of some kind in there? There's a thin hexagonal shape around the hole. I put a socket on it thinking I might unthread it, but it didn't budge and I didn't want to lean on it too hard.

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#7 Old 03-17-2010, 05:45 AM
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Originally Posted by buck99 View Post
I had the same problem with my rad so I ran a 1/4 NPT tap into the hole.
Works now.
Hmmmm....there's an idea.

___________

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#8 Old 03-17-2010, 10:10 AM
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Originally Posted by Megunticook View Post
Could be...why the @##$!& would a big old radiator for an old American vehicle have a metric thread, though? Seems odd.
Probably made in china.

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#9 Old 03-17-2010, 06:00 PM
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Some after market radiators just have a plastic plug for a drain.
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#10 Old 03-17-2010, 11:23 PM
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yep sure do ^^
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#11 Old 03-18-2010, 09:55 AM
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Originally Posted by Awingandachair View Post
Some after market radiators just have a plastic plug for a drain.
Hmmm, let's see, a new brass petcock retails for maybe $3, which means it costs probably $1. A plastic plug costs maybe $ 0.25. So the business geniuses at Proliance are making an extra 75 cents on a $180 product by substituting a plastic plug for a proper petcock. And in the process the customer gets an inferior product because when you go to drain the thing you get coolant spilled all over everywhere.

Might this be the same business mentality that brought such financial success to GM?

I'll see if I can tap out that friggin' hole I guess.

I understand the need to be competitive in the global marketplace, but sometimes I think the folks running our nation's companies are just plain idiots.

But hey, no problem, I guess nowadays you can drive your company into the ground while lining the executive's pockets and no problem, us taxpayers will bail you right out and you can do it all over again.

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