Spark Plugs and Water
 

I must say - changing the plugs on a MKIII can be a bear. Afterwards, the car runs smooth, but it did leave me with a related question...

Just before the change, I was cleaning my engine due to a recent oil leak. I thoroughly sprayed it with Gunk Engine Degreaser Gel (worked great, but only if the engine is warm). One of the areas I cleaned was the general vacinity of the spark plugs, and after doing so, when I removed the boot on the plugs, the cavities were full of water!

Is there no drainage hole? As I sometimes have a stubborn engine just after a good rain, and have had similar issues with spark plugs on a motorcycle that would not drain, it got me thinking. What can be done to prevent this?

Nope, no drain in the plug valley. The #3 gasket for it is mostly to keep large pieces of debris from falling into the plug wells, and any liquid which gets caught there stays there until it evaporates (or you sop it up with something). Can sometimes cause firing issues, but there's not much you can do to prevent it other than stuffing dish-rags or something into the plug wells before you hose the engine down.

BTW, if you start getting oil in the plug wells your #3 gasket may need replacing, or it could be the valve cover gaskets.