If you can measure out the thread size etc, it’s a candidate for 3D printing. Yeah that’s a pretty useless observation.

But I’m curious , is the mm measurement the major diameter of the male part sticking down from tank? 

Alistair 

> On Jun 29, 2019, at 12:51 PM, Jack Elliott <pdaxe2gto@gmail.com> wrote:
> 
> No, the original cap is long gone. I do have a reasonably not terrible
> solution that only loses about 1 drop of water per every 10 minutes. At
> this point it's become a puzzle I'd like to solve! VW lists 34mm and 35mm
> as their options. Clearly I am not the only owner with a tank that takes an
> unknown thread size.
> 
>> On Fri, Jun 28, 2019 at 5:41 PM Stephen Grisanti <bike2vcu@yahoo.com> wrote:
>> 
>> Do you have the original cracked cap? When that happened to mine I glued
>> the halves together and then set that repaired cap into a PVC end cap from
>> the HoDepot plumbing department and glued it in place for reinforcement.
>> Leak free for years now.
>> 
>> Stephen
>> 
>> On Friday, June 28, 2019, 11:00:26 AM EDT, Jack Elliott <
>> pdaxe2gto@GMAIL.COM> wrote:
>> 
>> 
>> The drain cap for my 84 Westy's freshwater tank developed a crack. The
>> online vendors give us two size options: 34mm and 35mm. The smaller 34mm
>> (P/N  253-067-285A) seems to be the correct size for this model year, so I
>> ordered one from GoWesty.
>> 
>> It's too large, turns without engaging the threads. I double-checked the
>> dimensions with their customer service dept. and it's clear that they
>> didn't send the 35mm one by accident.
>> 
>> So . . . here's what I'm looking at: a Westfalia OEM water tank (GoWesty
>> also looked at pictures of the tank I sent and agreed this is a stock
>> tank); with a drain pipe that has an o.d. of 34mm for the unthreaded
>> portion; and the threads are in quite good condition with no sign of
>> stripping, cross-threading, or wear. Nice sharp edges.
>> 
>> Yet the 34mm cap turns and turns without tightening.
>> 
>> I have a clunky fix installed, using a PVC ball valve from Home Depot and
>> it works ... but still, is there some odd smaller-than-34mm size rarely
>> seen?
>>