Quote:
Originally Posted by dc_wright
The down side of this approach is that you're just displacing the clogging debris back up into the water collection funnel. Unless you're then going in from the top and vacuuming out the funnels, the next time it rains the same debris gets deposited back into the drains. The reason for using the vac method is to try to actually remove the debris so that new debris has to work its way in there and collect in the drain tubes.
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If your car is dry (and the drain channels too), you see the small leaves&twigs flying out of the slits by the roof from the blast of air.
But blowing is always much more powerful than suction, both in force (more than a factor 20) as in direction. And stuff comes out easier the way it came in, so I believe that blowing from below is a more secure way to unclog than suction from below.
But if you can get a vac. in from above, that would be a good way to clean up debris that was left behind by the compressed air.
I use a cheap ebay endoscope to look if there is debris.
Sometimes when I clean cars I make a thin hose (1/2" or so) on the shop vac to clean stuff in creavases on cars when there's wet debris (not necessarily on z4's but general; for example between hood latches and bodypanels etc)
Regarding the spraycan with air: that has not that much power and air. Buy a cheap compressor and a blow gun
Compressed air is also a great way to dry your engine when washed (sometimes that has to be done....). You can blow the water out of the connectors and hard to reach places. (don't use compresses air on soft materials like sound dampening etc)
(probably more useful in wet hars climates and cars that are stored outside than the dry and conservative climate in california etc)