99 lumina over heating.. help

temp sensor may be bad telling you it's hotter than it is... Bubbles in the lines or block keeping it from cooling properly... Or thermostat could be stuck...

I was a mechanic for a GM Dealership for 9 years and this was what I found. If this has the 3.1 or 3.8 v-6 it could probably be the intake gasket. The intake gaskets on these engines were made of plastic and would detereorate over time due to the heating and cooling cycle of the engine. These were tricky to diagnose because sometimes when they leaked you would not see any coolant leaks because it would leak back into the engine. Does the coolant jar always appear to be low? Does the coolant appear to be dark and dirty after changing coolant?

The V-6 is terrible about air pockets. It usually takes a lot of time and patience to get them out.

no it isn't low usually and no never dark or dirty. yes, it is a 3.1.

I totaly agree with jesse its the intakes for sure it very common on those engines. when you replace them make sure to use a vacuum coolant filler to eliminate air in the system. oh yea if its not leaking externaly you can pull the spark plugs and see if they have a white film burnt on any of them this is coolant being burnt

there is no way to accurately diagnose a vehicle without having it in front of you stop guessing and hoping, take it to a certified gm dealer, not your corner street mechanic.

your thermostat could be the problem,also agree with intake gasket hav replaced them to .start with the basic first.

Thanks Mark, I am trying in the 34613 area code to find a mechanic who does not charge an arm & a leg, near me they get $84.00 an hour for labor only,they did not give me a quote how much the parts are, I am an older female, and like to see these quotes. The list they gave me was a R&R intake, Intake gaskets Valve cover for gaskets, thermostat Lof, no idea what this is, also a used intake

I know there are many experts here but for sure sharing some experiences about Heat or engine heat is good to people who can save money which mechanics are taking some times of no knowledge. 2006 Lumina I am driving is having a radiator cap which is having a spring inside it which opens like a value when the presure is high or heat is higher. which controls the presure of the engine and water tracks. When water is less this cap lifts up and take from reservior. and most of the reason of heating is this cap. we need to replace it due to rust in it and the uncapability of moving up and down. The other reason may be the sensor of heat is required to change. or the valve which is installed needs replacement. Some times the fans dont work due to the motor of the fans has taken its life time running. or a cut out is needed to be changed. At the same time if there is a water decrease every day you open the radiator cap in the morning and there is water in the reservior at the same time every thing is ok the cap needs to be changed as it is not helping recover the decreas. Quick checks are. Fans working tick ok, cut outs all are ok tick ok. water not leaking from below tick ok. replace cap first. if still problem remains the same than check the oil is not less. the transmission oil is not less. if all ok than only reason will be the sensor problem and the walve. or the water pump blockages