Swirl flaps and the problems they may cause first began to be raised as a possible problem to BMW car owners on 14th June 2007 by members of BMWLand, so members wanted to prevent costly repair bills.

The BMW inlet manifold have swirl flaps which are designed to create a swirl of air to improve combustion under light load and to reduce a slight increase in emissions from soot due to a lack of air. The flap is closed by an actuator during light load, idling and fully open during engine load to maximise air intake and increase engine output.

The problem with swirl flaps is that when they fail, the rivets/screws can get sucked into the engine causing damage to pistons, valves, cylinder heads and damage to the turbo which results in several thousand pounds worth of repairs.

BMW introduced an improved and stronger swirl flaps to address the issue in 2004, however there have been reports of the newer design failing and this obviously becomes more of a risk as cars start to come to the end of their warranty.

BMW swirl flap failure can result in a repair bill of several thousand pounds and there are many reported incidents of BMW swirl flap failure on the internet. There are three options for BMW swirl flaps if BMW car is out of warranty:

1) Leave the swirl flaps as they are and hope they don't fail
2) Every two years buy a new manifold to keep it within BMW warranty
3) Buy swirl flap blanking plates and have peace of mind that nothing can fall off & get sucked in to your engine

source: http://www.bmwswirlflaps.co.uk/