Thank you for your quick response!Its been 4 hours so I went out and checked the overflow tank and radiator.the overflow tank had went down a little,I think I put too much this morning but it leveled

You have a coolant leak. The engine gets hot and pushes coolant out under pressure into the overflow tank.When it cools, the volume of coolant decreases, the pressure drops to the point that it becomes a vacuum. The vacuum pulls in air more easily than coolant. It's thinner. So, you keep losing coolant from the radiator which makes the engine run hotter, each time until it eventually overheats and does damage. You need to have the cooling system pressure tested. The leak will show up. Usually, it's a loose hose clamp or cracked radiator tank high up, which makes it had to see the coolant because it doesn't leak much and it boils off leaving little or no evidence. Fill the system completely before pressure testing. Remember, checking the overflow tank means nothing when checking coolant level. There's no short-cut to checking the coolant level, take the radiator cap off when cold to accurately check level. Read the safety precautions on the car but always check when the engine is cold. NEVER HOT.

Hi Larry:
Good observation. Not too many people would spot that.
When the engine is hot, the coolant is hot and expands. At the filler cap for the radiator, there will be a hose that goes to the overflow tank. As the coolant fluid expands, it flows through thie tube into the overflow tank.
When the engine is turned off, as it cools, the volume of coolant in the engine and radiator contracts, and is supposed to suck fluid back from the overflow tank.
I'm suspicious that something is preventing this from happening so the vacuum in the engine coolant system is collapsing the hose.
WHAT TO DO?
- Check the radiator cap. Make sure it is functioning correctly. Make sure that it is correctly installed and screwed all the way on.
- Check the coolant overflow hose. Make sure it is not plugged.
Odds are that you will find the problem quite quickly.
Cheerfuls.

have a compression test done as that will most likely be a blown head gasket or cracked head allowing combustion pressure into the cooling system. A quick check is to remove the radiator cap and fill right to the top . Run the engine and if you see small bubbles in the water or it tends to belch out then it will be the gasket of cracked.

Raise the car front end as high as possible with a floor jack, fill the coolant tank to the top, run the engine until it reaches just short of overheating, shut it down and run water over the radiator, this will burp the air out. Repeat as needed. Don't let the coolant recovery tank run dry during procedure.

Check that the fan is working. You do not give a make or model, so it could be the thermostatic switch, fuse or relay for an electric fan or the viscous clutch if it has that type of fan. If the water bubbles out or you see bubbles either in the radiator or the overflow, you might have a head gasket leaking into the coolant system.

might not be a radiator capon this one - some mfgr's went to that design,. to fill it would be the overflow tank.
Possible thermostat or water pump issue..
Ck

Your overflow tank works on suction to return coolant to the radiator. Check the line and nipple ends for any cracking (cracking on the plastic radiator nippl is very commom). The radiator nipple is not under high prrssure like the fluid under the cap (inside the coolant system). It's on the otherside of the cap and will never "stream or gush" coolant (uless you are over heating badly). As the coolant in the radiator cools it creates a vacuum and draws coolant back from the overflow throgh a small hose. You might not see any leaks as coolant heats up and travels to the overflow. It might be a very small leak and you are usaully driving around and drying up before you see it. Even with a very small crack it will only draw in air and not liquid (as liquid is way heavier than air). Also, I've seen where people have taken out (or fallen out) the tube attached to the overflow cap that goes down deep into the overflow tank. That tube should be long enough to almost reach the bottom of the tank. It's hard to know if something is missing if you do not know it was suppose to be there in th first place but it needs to be there.

There are 4 things you want to check in this order.
1. Make sure your fluid level is up to specifications.
2. Make sure the fluid is travelling through the radiator freely(water pump).
3. Make sure your thermostat is opening. This requires a great deal of caution, leave the radiator cap open (if it has one) and run the engine until the top radiator hose gets hot, If you have no radiator cap, watch for water rising or dropping in the overflow tank.Also watch for bubbles within the overflow or radiator.Also put all temp controls on high on the climate control center and feel for hot air once the engine reaches operating temperature(185-200 degrees). If you don't get heat within the regular time slot of 10-15 minutes you will need a new thermostat.
4. If you discover a large amount of bubbles within the radiator or the overflow tank than you've got a headgasket situation and should not drive the vehicle until necessary repairs are made. Thank you, Dana

about 100K miles? sounds like a blown head gasket is allowing coolant to be pushed out the exaust,and combustion pressure is pushing fluid out the overflow.have your compression tested.

leave the overflow tank cap off and start engine. turn your heater setting to max heat and fan on highpour 50/50 mixture of coolant till you see the coolant at the proper level on the tank. wait for the vehicle to reach optimum temp about 180 degrees. you should feel; the upper radiator hose it should be hot. then check level of coolant in overflow tank fill to proper level if neccessary. A quick note if you continue to lose coolant and can;t find a leak chances are it's being burned in the cylinder and this would mean you have a blown head gasket. to check this just start the vehicle the next day if there is white smoke yo have a seeping gasket if it's a constant white smoke then it's a severe problem and needs to be repaired immediately or you will warp or crack the intake manifold , the head or the block.. please rate this........thanks