Radiator reservoir keeps emptying - 2001 Mitsubishi Galant

Maybe it's not over heating , the gauge is bad .
Coolant not emptying from the reservoir to the radiator until the car turns off. That's how it works , doesn't draw coolant while vehicle is running . System under pressure , too high of pressure an it sends coolant to the reservoir, when you shut the vehicle off as it cools down it draws coolant back into the radiator. Your best bet , take it to a qualified GM technician . The man who knows your vehicle best .

It could be anywhere in the cooling system, a hose, the radiator, the engine block, the head, or any gasket between those points.

If you can't keep fluid in the overflow you either have an external leak, you should see fluid on the ground after stopping, if no fluid is apparent you have an internal engine leak and need a mechanic to determine the cause and repair.

Check the water pump and see if coolant is around it.

1. Check the hoses and clamps going from the reservoir to the radiator and from the radiator to the engine. Make sure they are flexible and in good condition.
2. Check the reservoir and radiator for leaks.
3. Replace any parts they may be failing. If no leaks are found proceed to next step.
4. Check engine oil. If oil has coolant in it you may have a blown head gasket or crack in the head or engine block. Another sign of a coolant leak into the cylinders is white smoke coming from the exhaust after the engine is warmed up.

So the level keeps dropping in the reservoir? If you have to keep adding coolant to the reservoir, the system is leaking or losing coolant somewhere. Have the system pressure tested to find the leak. Is the reservoir itself leaking? When the level gets low enough, first the reservoir will go dry, then the radiator level will start to drop.
Here's how the reservoir works: coolant is under pressure from the radiator cap seal. As coolant heats up from hot engine, it expands, and pressure forces the radiator cap seal up, coolant is forced into the reservoir-remember the hot mark on the reservoir? When car is shut off, coolant contracts, creating a vacuum in top of radiator. This vacuum works to suction coolant back from reservoir into the radiator, keeping the radiator topped up, and coolant should now be at the lower cold mark on the reservoir. It is a closed, sealed system. The only loss of coolant will be a very small amount of evaporation from the reservoir. If coolant level keeps dropping, there is a leak somewhere.

You can buy a 50/50 mix of coolant and water. Use that. And dont use tap water it can hurt your engine. If your loosing coolant check all your hoses for leaks and your reservoir for leaks.

Hi Tiffany,

The engine coolant does not "circulate" through the reservoir in your Jeep. This system works on the fact that things expand when they are hot and contract when they are cold. When the radiator is full, the coolant expands when the engine gets hot and the overflow runs down the small hose to the reservoir. When you shut the engine off, the coolant contracts and a vacuum is created inside the radiator causing fluid to be drawn out of the reservoir and into the radiator. When you start your engine and it gets hot, the cycle begins again.

If the radiator is empty, this sytem cannot work. There will not be enough vacuum generated in the radiator to draw the fluid from the reservoir (too much empty space and not enough coolant contracting as it cools).

You need to find out WHY the radiator is low. If it is low, there is a reason for it. Either something is leaking EXTERNALLY like a hose or water pump, or something is leaking INTERNALLY like a blown head gasket or a cracked cylinder head. Proper diagnosis is recommended.

fill the reservoir with the coolant. it is a GOOD thing you dont see steam or a leak I hope.YOU DO WANT TO CATCH THE PROBLEM BEFORE IT REALLY OVERHEATS OR YOU MAY HAVE MORE COSTLY PROBLEMS. fill the reservoir. BUT, it may only fill the "radiator" once you do this as it cools off. As the radiator water cools it sucks the reservoir water into the radiator. as it heats up and the water swells (increases in volume) it pushes the excess into the reservoir. when the engine is good and hot and you dont have any coolant in the reservoir, that is a sign that the radiator is low or empty also.
when the engine is cold, find the radiator cap and remove it, add as much coolant you can there. fill the reservoir also. If it has been several years since the radiator cap has been replaced, I would do that now ( it is a cheap investment). if the gasket on the cap is not sealing well anymore or the exspansion valve mechanism on the cap is not working properly anymore, then it will let coolant pump out into the reservoir and not hold radiator pressure. if the reservoir is empty the radiator itself is probably too low or empty.

I hate to tell you this but its possible...

You have a leak. Look around on the driveway and try to determine if you have an external leak as opposed to an internal leak. If you see no coolant on the ground, suspect a blown head gasket. Do not continue to drive this car in this condition. If it does indeed have a blown head gasket, serious engine damage will occur.

Check your exhaust for white smoke. Chances are good you have a blown head gasket and coolant is leaking into the engines combustion chambers and is essentially burning off. Also check your oil, if it looks like caf mocha, this will confirm coolant is leaking into the oil via the blown head gasket