In addition to the seal at the bottom, there is a rubber seal at the top,
under the part that looks like a removable cap. Carbon can build up around
this seal and/or it can split (I cut my old one open and posted a picture
here: (
https://www.thesamba.com/vw/forum/viewtopic.php?p=8756021&highlight=#8756021
).

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On Sun, Jan 20, 2019 at 12:00 AM Dennis Haynes <d23haynes57@hotmail.com>
wrote:

> While the oil itself may be able to withstand temps that high there is a
> difference from hitting the bottom of hot pistons or cooling bearings and
> the "bulk" temperature of the oil in the sump getting that hot. Just like
> the cooling system there are parts that are much hotter than the
> temperature reading at the gauge. That is why it is so important for the
> cooling system to maintain pressure to prevent vaporization. Anyway, for
> the Waterboxer a lot of bad things happen when the oil temp gets out of
> control. The first is the drop in oil pressure. This is due to the oil
> viscosity dropping and over expansion of parts of the engine causing
> clearances to increase.  VW added the oil cooler on the 2.1L engines to
> keep the oil temp close to coolant temp. At times it just isn't enough.
> Even with the oil cooler in Fun Bus oil testing has shown oxidation and
> nitration is happening, most likely due to high ring temp temps. Getting
> back to the oil tower question I have replaced many an o-ring at the base
> and the towers themselves du to them getting distorted or even melting
> where they sit on the crankcase.
>
> Dennis
>
>
> -----Original Message-----
> From: OlRivrRat [mailto:OlRivrRat@comcast.net]
> Sent: Saturday, January 19, 2019 10:11 PM
> To: Dennis Haynes <d23haynes57@HOTMAIL.COM>
> Cc: vanagon@GERRY.VANAGON.COM
> Subject: Re: breather tower
>
> On 19 Jan , 2019, at 2:23 PM, Dennis Haynes wrote:
>
> > Again from overheating that seal can fail also. BTW the crankcase and
> engine oil can over heat even with the coolant temperature indicating all
> is normal. Enough speed and load or over filling can easily get the oil to
> 270F or more.
>
>         While 270ºF is Pretty Darned Toasty it is not OverHeated,
> Especially if using a High Quality Synthetic ~
>
> The Mob1 15w50 is Good to 500ºF According to the Mob'Guys ~
>
>
> https://eur03.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.mobil1racingstore.com%2Fmobil-1-15w50-122377-oil&amp;data=02%7C01%7C%7C8a747041879d4e75c41708d67e84dbf9%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636835506417353785&amp;sdata=blJf79CgTU7jvvyUDjrfJEBFAGDKS5R0v7DYJRgPXIM%3D&amp;reserved=0
>