What is the process.
I had to install an new overflow bottle and don't want trapped air.

do i simply start the car with the cap of overflow bottle?

I don't think the actual radiator has a cap.

 

If you didn't drop all the coolant and just replaced the bottle you should be ok .

 

yeah just overflow and a few pipes.
started it with cap off.

got it up to temp and put it back on. i assume there's a relief valve somewhere but it seems okay.


Now I'm never letting anyone look at the car, when I have the hood up a passer by leaned on the bottle and snapped an end off it.

 

usually you disconnect the pipe that leading into the top of the overflow reservoir from the front and point it down and keep adding until the water that comes out is solid and consistent. But I suppose getting the engine up to temperature will open the thermostat which should get rid of air when the water starts flowing.

 

The system is "self bleeding". Just make sure you run the heater for a while so the valve opens and bleeds the heater core, too.

 

I have done this several times. Just add coolant. Wait until it won't take any more and then drive around and check/top it up periodically for a couple of days.