Aaron, like Dave said, that's the oil pressure relief valve. Leave
that alone. Only a couple of reasons to ever go in there!
Miguel

'In heaven all the interesting people are missing.'
  - Friedrich Nietzsche

On Wed, Dec 30, 2009 at 6:13 PM, Dave Mcneely <mcneely4@cox.net> wrote:
> The "big plug" is the port for the oil pressure bypass valve.  The
> coolant is coming from somewhere else.  It could be from the water pump,
> or from a head seal leak.  DMc
>
>
> On Wed, Dec 30, 2009 at 6:07 PM, Aaron wrote:
>
>> Hello all.
>> I just noticed a coolant leak out of what appears to be a drain plug
>> in the engine on the driver's side of my '87 westy. It's flat, about
>> 1" across with a slot in it and sits just to the left and behind the
>> oil drain plug. Anyway, I'm not sure if it's plugging the cooling
>> system, but it appears that coolant is leaking out of there.  I
>> suppose it could be the water pump as well, but it didn't appear to be
>> dripping down from above. I'm planning on doing some driving this
>> weekend and wanted to hear opinions on:
>>
>> Is the big plug likely where it's leaking from?
>> Will this leak get worse?
>> What's the best way to fix it?
>>
>> Thanks!
>> Aaron '87 Westfalia
>