The ford service manual states that u need to leave cap off while temp rises till operating, add coolant as the level drops after thermostat opens, then replace cap..

is that right?
or did I read wrong?

 

 

That is correct so you don’t have to remove a hot radiator cap under pressure. You also need to have your heater set all the way to hot and blowing.

 

Awesome..
many thanks..

 

I just flushed and refilled my coolant system. I'll tell you that if you drain the block on the left side and drain the radiator in my case only 2.5 gallons came out, so I put 2.5 gallons of concentrated in after flushing several times.
I didn't warm up the truck I just filled the reservoir to the top then put the cap on drove around did my errands with the heater on. Came back and the level was just at the bottom of the reservoir. I put some distilled water in to to fill line and it was good after that.