Empty coolant reservoir - 1990 Volvo 740

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 .

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

You must have a coolant leak. If there are no signs of a leak, you may have a gasket on the engine that has gone bad, and the coolant is being pushed out the exhaust system. The coolant expands when hot and cools when the engine cools. During the cooling stage the cooling system creates a suction on the coolant in the reservoir and draws enough coolant back into the system to keep it full. Apparently you are loosing enough coolant somewhere that the reservoir can not fill the system before going dry.

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.

It probably got overfilled at some point. There's a max line on the reservoir that you shouldn't fill it over. Coolant expands as it heats up so if there's too much in the system, it's normal for it to overflow.

Cooling problems can cause damage to your engine.
please have it checked out.
could be on of many problems.
Coolant level
Water pump
thermostat
fan
fan controls
drive belt or tensioner

Good luck

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.

Fill the coolant system back-up to level and pressure test the system. Check for chalky, white trails, antifreeze trails, spots on the ground, and see that the pressure is holding for more then five minutes. Could be: head-gasket, freeze plug, hose, heater core, water-pump, or radiator.

I guess the burning question is , where is the coolant going.
Is this a 4.3 engine? How many miles does the vehicle have?
Has the intake gasket been changed?
I'm guessing a can of "Bars Leak" may cure your problem.
Let me know.
Regards,

water pump