bf falcon rattles

[john gordon]

my bf falcon started a strange rattle coming from the left front. I took it back to the ford dealer and boy, they went over everything. From re-tensioning caliper clips to fitting new grommets on brake lines that run along the chassis.Everything under the bonnet is now more secure than Fort Knox.
Alas rattle still there.
The rattle would stay until the car warmed up, not only in motor but body
It started about 3 weeks ago when it got really cold in chch
A mate of mine is a panelbeater and he found it in 5 mins.
Cold weather plastic shrinks. hot, it expands. The bloody bumper was rattling against the front guard and when temp went up rattle stopped.
solution;took off bumper, cleaned up and re-fitted .Rattle gone