When combustion gases get into the cooling system and blow out through the cap  they will destroy the cap in the process. The later disc caps also seem to be designed that during a failure they will fail open. If the caps tests good on install and fails in a short time it is most always due to system problem.

Dennis,
From my phone.
________________________________
From: Stuart MacMillan<mailto:stuartmacm@GMAIL.COM>
Sent: ‎7/‎17/‎2016 3:23 PM
To: vanagon@GERRY.VANAGON.COM<mailto:vanagon@GERRY.VANAGON.COM>
Subject: Re: WBX Cylinder Head Nut Torque check, re-torque

No, it's just poor quality!  When mine fails I'm going to cut it open and see what's inside.  I'm pretty sure It's just a rubber flap valve, which will fail over a time period in proportion to the quality of the rubber used.

A true reproduction of the OEM valve would likely cost $100 or more.  Maybe worth it, but it's stuff like this that keeps reinforcing my desire to convert to a Subaru engine.

Stuart

-----Original Message-----
From: Neil N [mailto:musomuso@gmail.com]
Sent: Sunday, July 17, 2016 11:28 AM
To: Stuart MacMillan
Cc: vanagon@gerry.vanagon.com
Subject: Re: WBX Cylinder Head Nut Torque check, re-torque

Right ok. I should've put OEM in quotes.    ;)

I have to wonder if a slightly hot running engine is part of what kills off these caps so soon. e.g. one being used in a bus with a less than efficient radiator.

Neil.

On 7/17/16, Stuart MacMillan <stuartmacm@gmail.com> wrote:

> OEM has two meanings with regard to parts for out of production vehicles.
> First, OEM means “original equipment manufacturer.” ....
>
>
> Regarding the cap, the OEM cap had a stainless steel valve and spring
> inside and a steel base.  The current ones don’t.

--
Neil n

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