My 97 keeps trying to dump coolant into the overflow, then overheats. I changed the thermostat, and got a new overflow. Flushed the coolant-twice. Got it pressure tested, and there are no leaks. What else can it be?

 

Air trapped in the system?

 

failing radiator cap.

 

+1 Yep, forgot about that battle last winter...

 

How do I get that air out?

 

What would a failing radiator cap have to do with it, what fails about it?

 

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a failing radiator cap can allow the coolant from the motor to go into the overflow when the system heats up and when it cools it lets air into the radiator.

 

when you bleed it park it on the steepest hill you can with the front of the car on the up side. when changing the opti i have left the front of mine on jackstands and filled the radiator and did a pre bleed and refill the let it set overnight and refilled the next day before starting, if you wait for the motor to warm enough to open the therostat then you are going to see an overflow from the expansion of the coolant. ok ill go through this for you, get the front of the car up, let it cool and fill the radiator, open the lower bleeder/bleeders and close when coolant comes out, refill the radiator and start the car with the radiator cap off, if the coolant level drops refill and put the cap on, now bleed the air out of the bleeder on the hose by the alternator. if on jack stands turn the motor off and lower, then take it for a spin around the block and re park on a hill with the front up. let cool and re fill the radiator,open the lower bleeder to check for air. put cap back on and start, bleed the bleeder in the hose, and take it for a spin around the block. redo this till you get no air.

 

my problem isn't that it is going into the overflow. My problem is that when it tries to put the coolant into the over flow, it doesnt go in. It just dumps onto the ground