My hhr ss has a 2 litre engine. A mechanic put new brakes on the rear, the front brakes were okay, but it still stays down on the floor when I shift. The Dot-3 fluid was full. No apparent leaks, and it works better after the car warms up. Do I need a new master cylinder or could it be something else

It started two days ago, while driving when I reach about 30 mph this noise starts that sounds like a wide open outboard motor. What could this be? Turning on or off the a/c fan does nothing.

It also when i floor the gas peddle the turbo starts to kick-in b
ut it don't and i was watching and the engine lite started to flicker as soon as i let off the gas peddle it went out? When the engine lite came on i called on star they came up with a code that the cam timing sensor problem. Can you tell me alittle bit about this please?

Engine cranks but does not turnover.