My 2003 Galant has a lound knocking noise when started on 50f and below freezing temps. It eventualy goes away after warming up to Normal running temp.

The 3.4L engine has special pistons that are designed to expand as the engine heats up. When the engine is cold, the pistons make a knocking sound that resembles lifter noise or piston slap. As long as the noise goes away after the engine warms up, don't sweat it; this is normal.

Sounds like excess bearing clearance, when the engine sits overnight the oil between the bearings and the crankshaft is able to run back into the oil pan. When you first start it up it takes a few seconds for the oil pump to fill the spaces back up and you get some clatter.

this engine has forged pistons whitch expand more than hyper-u-tec-tic pistons when heated . this is normal for this engine . my brother has a chevy silverado 2001 1500 4.8Lwith 650,000 kms and he said his made that noise when it was brand new and the dealer said this is normal. the truck still runs like new with lots of power and it still makes that noise before it reaches operating temp then goes away.My brother uses lucas oil treatment and it helps quiet the knock a little when cold.

Your cataylic convertor is going south thats the rattleing noise eventualy it will clog you may get a couple of years at best but you need to start thinking about replaceing it

make sure first you check your anti-freeze level. one simple procedure to do is to see if both radiator hoses are the same temp after the car is warm up. if not suspect faulty thermostat.

WHEN COLD THEN GOES AWAY WHEN WARM. THATS NORMAL FORGED PISTONS SLOP WHEN COLD.I HAVE 01 SILVERADO WITH 390,000 RUNS GREAT 21MPG 40TO50 PSI OIL PRESSURE KNOCKS WHEN COLD THEN GOES AWAY. NOT A PROBLEM. IF IT DOSE IT WHEN WARM AND LOW OIL PRESSURE WORN BEARINGS NOT GOOD.

it may need a lifter or valve adjustment when cold they will tick or knock depending on how loose or worn out then when it warms up they swell with heast and noise stops. after adjusting or replacing it will stop making noise

this is a sign of worn engine components, sounds like piston noise and vlave train noise

THE HUMMING NOISE IS YOUR SECONDARY AIR INJECTION PUMP. THEY TEND TO BE NOISEY AT START-UP. IF IT IS NOT WORKING COREECTLY IT WILL SET A CHECK ENIGNE LITE. THE CLICKING NOISE IS NORMAL IF IT GOES AWAY AFTER WARM-UP. THESE MOTORS ARE NOISEY WARMING UP DUE TO THE HYDRAULIC LIFTERS.

This is Caused By the Grease in the Spindle Bearings Getting frozen. Get it Greased up really Well and you Might need to Repack the Bearings on this side to Stop this and Stop further Damage to the Spindle.