I have owned my 97 Catera for many years. I have learned everything bad about this series of Cadillac and there are many. One of the biggest problems with this car is overheating. In 90% of these cases, it is warped heads and/or the gasket cylinder head gaskets that have been eaten away and water is leaking into the engine or exhaust system. When the leaking cylinder fires, it blows hot exhaust back into the cooling system that super heats the water and causes overheating. If your Catera has overheated more than once and the temperature gage was well into the red, it has most likely warped the head. In most cases the coolant from GM has to be changed every 50,000 miles or it becomesacidic and eats out the head gasket. There was a law suit against GM for this coolant that GM lost. Other causes of overheating can be caused by a stuck thermostat, but the result will be the same, a warped head. I had to replace one head (to warped to resurface) and both head gaskets. There is a simple test for a blown head gasket. It is a blue solution that if it senses carbon dioxide it turns green. A tool that is similar to a turkey baster bulb filled with this solution is put into the overflow tank hole. By squeezing the bulb it picks up air and if the air contains CO2 it turns the water to a different color. Check with a place like PEP Boys or some place that has a garage to see if they have this tool in their shop. It is the easiest, cheapest, and most sure way of checking for a blown head gasket. If you do have a blown head gasket, you will likely have to have the heads resurfaced. A good machine shop will not resurface the head if it is warped more than 10 thousands, because it will just warp again.
check radiator for small leaks or cooling lines which would most definitely cause it 2 steam when running after awhile
Do not take a radiator cap off. Fill from the overflow tank or you will add air to the cooling system and it will have to be bled off or your engine will overheat.
your radiator clogged up.cheaper to get a new radiator. nothing to do with the radiator cap.
One situation that the overflow jug would cause an overheat condition would be if the hose and/or connectors were plugged up or blocked. NOTE: before disconnecting anything to do with the radiator, ensure the engine is COOL! The cooling system operates under significant pressure.
it is possible your radiator is clogged
With the engine cold, put it in the radiator just to be sure there is no air gap. Run it for a short time until it gets warm and coolant begins to circulate. Then install the radiator cap and put coolant in the overflow to the coolant level line.
I was having the same problem with my 99 explorer. What I discovered was that the overflow tank for the radiator was empty and was causing a false reading by the temp gauge.
Blown head gasket or bad radiator cap
Check the upper and lower radiator hoses at the engine. They have a tendency to expand and split.
It probley has an AIR pocket in the cooling system. Bleed the air out of the system and make sure it is full of fluid.
Try replacing radiator cap Is cooling fan working? Make sure radiator is not plugged or dirty Check coolant level water pump
The heater core has no overflow hose. Cooling system is a closed loop system and the only overflow hose is the one going from the radiator cap to the reservoir. A thermostat that is stuck closed will cause the engine to overheat. Drain and flush the radiator, replace the thermostat, install a 50/50 mix of antifreeze and distilled water, bleed air from the system. You may also need to replace the radiator cap. Be sure and replace these parts with OEM parts.The heater core has no overflow hose. Cooling system is a closed loop system and the only overflow hose is the one going from the radiator cap to the reservoir. A thermostat that is stuck closed will cause the engine to overheat. Drain and flush the radiator, replace the thermostat, install a 50/50 mix of antifreeze and distilled water, bleed air from the system. You may also need to replace the radiator cap. Be sure and replace these parts with OEM parts.