John,
Sorry for the mislead, looks like Gates no longer makes anything smaller than 9.5 mm.
That AutoZone hose is the right size but I think it’s fuel line, I wouldn’t do that.
VanCafe sells the silicone hose Dennis refers to at $13.50/meter.
https://www.vancafe.com/N90097601SIL-p/443121107asil.htm

From: John H. Lauterbach
Sent: Sunday, October 20, 2019 6:12 AM
To: Gene P; vanagon@GERRY.VANAGON.COM
Subject: Re: Hose from pressure cap on expansion tank to coolant overflow tank

Thank you, Gene. I would appreciate it if you would post the Gates Part Number for the hose you are using. I was able to find anything like what the stock hose is on the Gates website.

John

On Thu, 2019-10-17 at 18:53 -0700, Gene P wrote:
Probably not at all chains but at a local auto supply I got
Gates 5/16 (8.0mm) premium heater hose, made in USA.
It’s straight heater hose, buy what you need by the foot.

From: John H. Lauterbach
Sent: Thursday, October 17, 2019 6:07 PM
To: 
vanagon@GERRY.VANAGON.COM

Subject: Re: Hose from pressure cap on expansion tank to coolant overflow tank

Thank you, Dan.  I went to the local AutoZone and O'Reilly's and neither store
had anything close except for high-pressure fuel lines.  That is why I posted to
the list.  John

On Thu, 2019-10-17 at 17:44 -0700, Dan N wrote:
cut a short section of the hose and bring it to any auto-parts store andthey
will match it.
On Thu, Oct 17, 2019 at 4:15 PM John H. Lauterbach <
john@jhl.mgacoxmail.com

>wr
ote:
What are the correct dimensions (ID, OD, Length) for subject hose, andwhere
doI get it?  I have seen some hoses on list vendor websites that
looksimilar, butnot the same.
If one cannot get a direct replacement hose, what are the alternatives?
Thank you,
John