Put this here because it seemed to be a gauge/dash problem.
A rattle was sounding from behind the dash at tick-over. Driving or revs up and it went away but returned at low revs.
Drove me mad looking for it, feeling around up behind the dash and even inside the cowl trying to find what was loose.
Then I noticed it stopped just for a second if I pressed the brake.
It turned out to be the check valve in the brake servo !!
