'66 small block...refilling coolant

[Rob A.]

I've installed a new H2O pump and everything is back on. Is filling and refilling the overflow tank as needed the way to get all the coolant back in. Do I leave the cap off while doing this?

[Jack H.]

Re: '66 small block...refilling coolant

If you saved the original coolant you drained, then you know how much is needed. The system may not accept it all in one fill due to trapped air pockets.

But, fire the engine, let it come up to temp and it'll 'burp' out the trapped air. Shut 'er down and let 'er cool and she should swallow the balance of the coolant.

If you didn't save the drained coolant, then fill the system until it's full and fire/run the engine to temp, shut down and let 'er cool. Now, INTENTIONALLY overfill the system and go for a ride. The first time you shut 'er down, expect the system to expell excess coolant via the overflow hose. By the third thermal cycle, the system should have achieved its natural coolant level repleat with appropriate expansion space and stop 'puking' excess coolant on engine shut down....

[Duke W.]

Re: '66 small block...refilling coolant

Fill it slowly until the expansion tank is about half full. Push the car up and down by the bumper to dislodge trapped air. Start it up with the cap off. Don't touch the throttle so it stays at fast idle as it warms up.

When the thermostat opens the level should drop as coolent flows to the radiator, which will include trapped air that will escape out the small radiator vent hose to the top of the tank. Add coolant as required to keep the tank about half full and watch the temp gage and drop revs to 1000-1500. If it goes much over the lowest normal part of the range (180), shut it down, let it cool for 20 minutes, then resume the fill process.

Once the level stabilizes at about half full at operating temperature, put the cap on, and take it for a short drive - like around the block a couple of times. Then let it cool for about 30 minutes and check the level. Also check the level the next couple of operating cycles. The tank should be about half full when cold.

Duke

[Rob A.]

Thanks for the replies....I did save the coolant *NM*