Power steering return line
 

I need to replace the low pressure return line. Does anyone know if this is Special size or a typical 3/8.

It should be a standard size but probably not 3/8 inch, perhaps the metric equivalent of 3/8 inch?

Guess that would 9.5 mm

I'm trying to build a custom high-pressure hose. My measurements of the pressure hose are ID = 9.43 mm so that would be close enough; you should be able to use 3/8 inch hose.

Awesome, thank you so much!

Autozone Sells the 3/8" Power Steering Return Hose by the foot and some stores Sell it in a plastic bag with 2 or 3 feet of Hose.
Power Steering Return Hose Specification SAE J189

http://standards.sae.org/j189_200306/

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For PS return hose, Gates Lock - On or the Dayco equivalent works fine. Transmission cooler hose works too. There is some really thick wall stuff that doesn't seal so well so I avoid that.

Standard fuel hose will work in a pinch though long term it will deteriorate, the lined barrier hose may have a better chance.

I used 3/8" Gates Lock-On hose for my thermostat hsg bleed to coolant pressure tank and it clamped just fine.

Pretty sure I used 3/8" on my swap, just standard stuff the parts store had. ~13k miles and no leaks.

I can attest that air brake line will last less than 2k miles.