I have a 1996 Olds Ciera which has 110,000 miles on it and I am on my second engine. The engine has around 40,000 miles on it. last week the temperature gauge started climbing,then falling back to normal when I started driving. If the car is sitting idling the temp stays stable. I replaced the water pump and thermostat and the same problem persists. It will warm up very quickly, then stabilize, then shoot up again. the heater will blow cold air intermittently while this happens. The temp also fluctuates if I make a turn. It doesn't seem to be using antifreeze, or not enough to notice since this just started this last week. There is some condensation coming out of the tail pipe. I believe I purged all of the air out of the system. When I rev the engine with the cap off the fluid level goes down, and then comes back up. There seems to be some bubbling in the coolant and overflow while running. The upper radiator hose is hot, so there is flow.Could this be a head gasket or manifild leak? i am going to attempt the repair on my own but want to be sure this is the problems. When the engine fully warms up, the temp remains stable.Thanks, Rick

Is the vehicle puffing white smoke at all?

Only when it isjust started up and cold. When it warms up, there is no exhaust that can be seen. Rick

I have a 95 Grans Prix 3.1 with the exact same problem. I have replaced the water pump, Thermostat, coolant temp sensor, radiator cap, radiator was removed and cleaned and flow tested, serpentine belt has been replaced. There is nort much left besides major engine problems. There is no antifreeze in the oil no white smoke.

when an engine head gasget fails, it can cause many very strange problems. one very common problem is called quenching. Quenching is a condition where coolant leaks from the cooling chambres into the combustion chambres. It is detected as a start followed by a stall when engine temp is normal, or in very minor cases a stumble right after starting at normal opp temps. does it do this?

Have you had the system press tested?...Does it hold press over time?

Any oily film on top of your coolant (black) after it is parked for a while?