Question is about the plastic tank 4 the radiator. I have a 2001 Taurus (3.0 Vulcan engine 12 valve) that had a crack in the tank. I replaced the tank and it keeps over flowing now. I put my old cap on because the new cap would not hold in the fluid. The old cap won't work either. While the engine is running it is O.K. but when shut off the fluid raises up until it starts coming out. My gauge reads center so it doesn't show overheating and when cold the level in the tank is fine. I did a cleaning and new fluid and that didn't help. Could it be the thermostat? Any help would greatly be appreciated.

 

Sometimes you have to play detective and determine why the original tank cracked. Just replacing parts is alright , but it gets expensive after a while.
I am very suspicious of a compression leak into your cooling system or a water pump pulling in air and sending it up thru the rest of the cooling system.

If you remove the radiator cap when the engine is cold, leave it off then run the engine, if you see the bubbles coming up to the neck of the radiator it would conform a compression leak into the cooling system. It wouldn't hurt to remove and check the thermostat. Air that is trapped in the system can also do this. hanky

 

The vulcan 3.0 does not have a radiator cap on the radiator. I found a sticking thermostat and weak antifreeze. Replaced the thermostat and added 70/30 antifreeze solution. Seems to have fixed the problem.

 

Thanks for reminding me . I have a 98 Taurus w/ 3.0 engine and if I didn't get so involved in the theory of operation of things I would have remembered that it has no typical radiator cap. Glad you corrected your vehicle's problem. Also I should have asked if you were referring to the radiator tank or overflow tank.
hanky