BMW e46 Plumbing – Convertible Drain Holes

Have you ever opened the trunk of you e46 convertible and found a wet and musty mess; you might have assume that the trunk seal was somehow involved. I did, and I was very, very wrong. After months of bailing my car like a row-boat, and much detective work — I stumbled on the culprit entirely by accident:

The Secret BMW e46 convertible drain holes.

As it turns out the mess in your trunk (and possibly in your back seat, mine is stained from water coming over the top of the rear bulkhead) has very little to do with your trunk or seals and almost certainly started in the compartment the soft-top disappears into while you are enjoying open air motoring. BMW soft tops have 2 layers the outer canvas and a molded headliner that insulates your head from the heat and the interior of car and look the business, however one of the layers in this molded headliner breaks down and falls in the convertible boot eventually clogging the drains.

If you have not done so yet, you will run to car look in the convertible boot, scratch your head, take another look, and then you are going to call me a moron. There can’t possibly be a drain down in there; BMW is very clever and German, surely if they put a drain … nope they didn’t. The drain is centered under that burly steel plate that together with the same bolts that hold up Golden Gate Bridge keeps the convertible top attached to the rest of the car. As you have already seen (after you called me a moron) there are no access holes to snake or blow the drain tubes. Score 1 for the hidden flaw that will flood your car.

There are only 3 options to deal with this man made problem.

1. Brute Force: Unbolt and remove the convertible top as one assembly. Yikes!
2. Sheer Luck: Fashion a tube with a slight bend at one end and try to chase the drain tube with .7 weed-waker line. Best of luck to you. I spent hours looking for the hole, cursed all of heaven and creation, and gave up.
   Nope you can’t get at the tube from the bottom. We said it was a secret tube.
3. Better Living Through Chemistry: Out of desperation I march to the kitchen and grabbed a bottle of Liquid Plumber and pour about a cup in each corner. Not entirely sure this would work I waited. And then as if by magic I hear lots of water pouring out in front of the rear wheels. Eureka!

Make sure to rinse with plenty of clean water or the same chemistry that saved you from hours of back braking labor removing the top, will kill you by asphyxiation.