I gave my 1992 wagon a thorough wash today, including some of the engine bay. I discovered that the right side cowl vent wasn't draining, which isn't surprising since the hole is ridiculously small, about the size of my pinky finger. I came up with a cheap solution that doesn't scratch anything up. I got a big Tyrap and cut the tip off to make a concave end. Then I poked and prodded the hole while trickling water on it, until - hurray! it drained away like an unclogged toilet. The purpose of the concave end is to capture the gunk and push it down. If the end is pointy, it will just slide next to the clog, wedging the two together. The Tyrap is flexible enough to follow a twisty drain hole, but rigid enough to be able to force out the clog. I used a pair of rose pruners to cut the tough plastic Tyrap with control.