The author of this chart says 5/8" for all heater hoses:
    http://www.loam.org/vw/Vanagon/VWtoNapaHoses/
The chart is for '86 - '91, but should be similar to '85.
Jerry

----- Original Message -----
From: "Jeff Lincoln" <magikvw@GMAIL.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Tuesday, March 09, 2010 10:07 AM
Subject: Heater hoses '85 Vanagon

> Hello -
>
> Can anyone tell me if the heater hose (that runs from the front heater
> core
> to the T fittings in the rear is 1/2in hose or 5/8in? I'm sure it's
> actually
> a metric measurement but the local FLAPS never seem to understand metric
> :)
>
> --
> Thanks,
>
> Jeff
> '85 GL (Gertie)
> '90 Carat (Grover - the noble parts donor)
> '86 (We call this one Scrap)
> '78 Bus (Melissa) Patty's Bus