My monte carlo overheats when idle but no signs of a blown head gasket nor water in oil. the temp gauge will go up to half way then the radiator fans will come on. when i'm driving it will go down to

milky oil is a indication of blown or leaking head gasket , or cracked head.

try a pressure test on the radiator while it engine is running.. If your head gasket is broken the compression of the engine goes into the cooling system. If the pressure rapidy increases it would indicate a head gasket problem.

you have a blown head gasket or leak at the intake gasket 9 out of 10 it the head gasket good luck....

If temp gauge is going into the red on a 3.4 engine it must be shut down or head damage can happen within minutes. I have a Monte Carlo that was overheating. I changed everything, thermostat, water pump, belt tensioner, radiator, all with no result. It would start out okay on a cold start but then I would come to a red light and the temp would creep up. Higher and higher until it neared the red zone. The heat would run cold. Most of the time, as soon as it was about to touch the red it would start to drop, the heat would blow hot again and all seemed okay but not for long. This would get worse and worse until the red hot light came on and I found myself on the side of the thruway. This problem is a blown head gasket. I had no other obvious signs, no white smoke from the exhaust, no oil in the antifreeze. I even changed the intake gaskets. Head gasket issues are common on the 3.4 liter engines.

Your engine is overheating, which isn't directly related to oil pressure. I would take the S10 to a reputable/trusted mechanic and have him perform the following tests.
Compression Test Leak Down Test Coolant System Pressure Test Inspect Oil for Moisture (you can do this one, remove the dipstick, does the oil on it look like milk? If it looks like milk it means there is water/coolant in the oil, a sign of a blown head gasket. However not all head gaskets dump coolant into the oil when they blow) Inspect Clutch Fan for proper operation
The mechanic will know what those mean, It sounds like your head gaskets may be blown, which is why the engine would be overheating. Also if the Clutch Fan isn't working properly, it won't pull enough air through the radiator to keep the engine cool at an idle or while sitting still.
If the Head Gaskets are blown, it doesn't necessarily mean you need a new engine.
One other thing to note, when an engine overheats, the oil breaks down and no longer works as good as it used to.

well,probably needs radiator replaced,burning off fluid smoking problem?if not going out exhaust or in oil,have radiator checked-replaced,if fan not running check relay and fuses,might need fan replaced,if you overheat engine to bad you will blow head gaskets and this is costly.check your oil,see if gray and milky,if so blown head gasket and water-antifreeze in oil,if going out exhaust will be blown head gasket inbetween the cylinders,fix radiator and fan first,but check out to see where all fluid is going.

I had problem with overheating on motorway when I drove over 60 mph i changed thermostat,radiator,thermostat housing, nothing helps.Then i find out that the problem was AIR IN THE COOLING SYSTEM try to squeeze all rubber pipes especially where is coming coolant to radiator.

That slushy brown stuff is signs of a blown head gasket. Have a code scanner hooked up to find out why the light is on, it will probably show coolant temperature sensor. Just out of curiosity, check the pvc valve (if your car has one), and see if it's clogged. If it is replace it, the crank case is not getting ventilated.

First when vehicle is cold like in the morning check and make sure that the vehicle has enough coolant/ antifreeze in radiator and reservoir. If coolant is need use a 50/50 mixture of water and antifreeze. You will need some time to do this let car run at idle until the temp guage is in the middle NOT+ normal operating temperature. At this point if the thermostat should be in the open position. Let vehicle run and check to make sure that radiator fan comes on. This should come on when guage is about midway/half way. If temperature rises above half going to h/hot and fan doesn't come on, you either have a BAD FAN BAD FAN SWITCH BAD FAN RELAY OR BLOWN FAN SWITCH FUSE. You will need to check all of the following I will help if its needed. If fan comes on and doesn't go off and vehicle continues to get hot even with fan running. Feel radiator hoses and see if the lower radiator hose is cool/cold. If it is you have thermostat that stuck closed. Replace thermostat and fix problem. If all the above is good and vehicle continues to over heat. THE BAD NEW IS THAT YOU MAY HAVE A BLOWN HEAD GASKET /CRACKED HEAD /BROKEN WATER JACKET. Basically you will need a HEAD JOB at least a head gasket. ONe tell tail sign of this is oil looking like milkshake/chocolate milk-a creamish while residue in oil or antifreeze. Contact if you need hel0p. Good Luck and thanks for using FIX YA