Chevrolet Repair: Re my malibu car 2002 model, upper radiator hose, radiator fan

Question
Dear Mr. John,

I own a malibu car model 2002, 3.1L engine and mileage of 105,000 kms. My first question is everytime i park on a nonflat surface( not level) overnight, after starting in the morning  sometimes i can hear sudden rough sound underneath like from the transmission or somewhere down there. Sounds like making some adjustment after the engine starts. Second question, the temperature gauge indicator goes up to two lines from the midline if running for sometime especially in a traffic area and aircon is off.When aircon is on, i got no problem. Gauge indicator remians at midline all the time. I noticed that radiator fan works only everytime aircon is on. Isn't it radiator fan automatically switch on once temperature goes up above midline.Is there somethign wrong with my sensor or is it normal to just keep the aircon on all the time. Need your help to solve these two problems  which i thought might give me more worse problem later.


Thank a lot,
Gary

Answer
Hello Gary...lets fix this! The single type radiator fan will activate any time the ac is on. This is normal.The fan relay is activated by a temp sensor right in the area of the upper radiator hose,near the thermostat.If you disconnect that single wire that goes to this switch, while the vehicle is running, the fan should come on. This tells you that the computer has grounded the fan relay and wants to cool the engine. If the fan comes on...change the little temp switch..ok the rattle...Check the shield that goes around the catalytic converter.Do this only when it is cold!The tin heat shield will rust and come loose. You might also need to change the filter and sump oil in the transmission..That noise ..buzzing...Might be the pressure regulator oscillating causing a ''buzzing sound'' Now go fix it!....Best