Oil Cooler Line Fitting size

[1BadBowtie]

I am making up my own oil cooler lines and I have no idea what size and thread the fitting into the radiator is. It looks like 1/2" NPT but I am not sure. I have attached the pictures of the radiator and older fitting.

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[df2x4]

5/8"-18 inverted flare.

 

[RDF1]

Its not going to be NPT which is a taper thread. It might be a metric thread with o-ring. Let me do some looking.

What about 1/2" straight pipe thread? I don't have a radiator with oil cooler to test it with so not much help. And cant find any info on the net

 

[RDF1]

5/8"-18 inverted flare.

Inverted flare doesn't use a o-ring does it?

 

[df2x4]

Inverted flare doesn't use a o-ring does it?

I honestly have no idea. I just know that I'd read 5/8"-18 inverted flare was the factory size for those radiator trans cooler line fittings, so that's what size -6AN adapters I bought for my 4L80E swap. Went in just fine, no leaks.

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[RDF1]

Do you need Engine Oil Cooler fittings or Transmission cooler fittings?

 

[1BadBowtie]

Oil Cooler right now. I will probably need the Transmission Cooler Fittings as well.

 

[RDF1]

Ah ok, I know the Engine oil cooler lines are a little larger than the trans cooler lines.
And the trans cooler fittings in the radiator are Inverter Flare. Engine oil cooler are Oring straight threads i think.

 

[df2x4]

OK that's the confusion. I saw those fittings and my mind defaulted to transmission, I forgot that some of these trucks have the in-radiator engine oil coolers as well. Those should be 20mm X 1.5 according to this thread.

http://www.gmt400.com/threads/how-to-install-an-oil-cooler-lines.30454/

 

[RDF1]

Now that is helpful right there!!