2000 malibu shooting coolant out the overflow?

You probably have a blown head gasket. In fact, the chance of this is about 90%, and I'm about to tell you why. First, those cars were only available with 1 engine: a 3.1 liter V6. The design for this engine was inherently flawed, but that's another story.

If you are using Dex-cool for coolant, then that is the problem. That's why you have a blown head gasket. Why? Dex-Cool was originally designed for use in military vehicles for the desert. Little did the Army know, GM had put together a low-budget liquid and sold it to the military for a very high price.

Soon, the military found out that this garbage actually became highly corrosive after about 6 months of use, and then slowly ate through head gaskets.

After eating through the gasket, it mixed with the oil, and turned to gelatin. Engines lost the ability to cool down, overheated, and craked heads, blew out rings, welded themselves together, etc, leaving soldiers stranded under fire.

GM then lost the contract to the military, and decided to unload the remaining Dex-cool on consumers. Marking the price up, they said it was REQUIRED in all their cars and trucks. Easy way to get rid of it all.

If that's what you use, that is why you now have a blown head gasket.

If you are NOT using dex-cool, you still have a blown head gasket, because that is the only way for the problem you described to happen. Replace the head gasket and switch to Ethylene Glycol - the normal old green stuff.

I believe your 2000 Malibu has a surge tank - the radiator has no cap but the cap on the plastic tank is a pressure cap. If it is the original cap (which I suspect it is) you should replace it with one from the dealer. Ten years is a long time for a pressure cap. Also check the surge tank for cracks and replace it if it is cracked. Those tanks can't be repaired, which is just as well - it would just crack elsewhere.

Because you say it doesn't get hot until it loses coolant, don't worry about other areas - stop the coolant loss under normal conditions and I bet your overheating goes away.

Michael S's answer is probably the answer but if not. read below

Not sure if the malibu has a belt driven fan, but it could be the fan clutch. Sometimes when the fan clutch becomes old it will slip, but seem to operate.

if the malibu only has electric fans they could be wearing out, if high mileage. Also check radiator to see if the fins are clogged with dirt or bug guts. you can pressure wash it at a local car wash.

if there is a crack, there will be allot of moisture in the tail pipe.

Also verify that the thermostat is sized properly (temp setting) your old one may have failed and then an incorrect temp thermostat was put in its place. Auto part stores and some mechanics don't do their due diligence to find the correct thermostat.

blown head gasket. you're pressurizing the coolant passages. orange gunk is in all probability rust buildup thats been sitting interior the engine block all this time. fill it up returned with water and go away the radiator cap off and crank it up, if the cap putting out starts spewing coolant like loopy, then you definitely maximum easily have a blown head gasket. don't be shocked in the event that they permit you be attentive to the top desires to be floor as its in all probability warped to hell and returned after being overheated that badly as its aluminum. optimistically, the block doesnt ought to be surfaced as properly as its aluminum too.

I agree with that guy, 100%. And also if you have a crack in that tank or any type of small coolant leak, it can cause it to do that. When the cooling system is completely contained, the system is under pressure, water and coolant have a much higher boiling point when they are under pressure, so any lack of pressure drops the boiling point and lets this boil out.

If it's starting to push out the overflow, check your radiator cap, it might me bad.

The other thing is you might have a compression leak across the head gasket to the coolant system and that would forcefully push the coolant out.